Georgina H. Endfield, Isabel Fernández Tejedo and Sarah L. O'Hara

Conflict and Cooperation: Water, Floods, and Social Response in Colonial Guanajuato, Mexico

DROUGHTS AND FLOODS are as much social constructions as physical occurrences. In recent years, historians have begun to explore the ways natural disasters are in fact shaped by human actions.¹ Geographers also have produced a large literature on the effects of natural hazards and rare or extreme events, and how the scale of impact can be determined as much by prevailing social, economic, and political circumstances as by the event itself.² To date much of the work by scholars in both disciplines has focused on the recent past and the present. To provide a deeper historical perspective on the social construction of droughts and floods, this article explores the response to those events in Guanajuato, Mexico, from the sixteenth century to the eighteenth century.

Guanajuato is an important case study for a number of reasons. First, it forms part of the Bajío, a lowland area in the central highlands (mesa central) of the country and an area subject to variations from year to year in precipitation, droughts, and floods.³ Second, although the Bajío, at the time of Spanish contact, as a whole represented something of a frontier zone—only the southernmost areas being permanently occupied—the area developed rapidly into a thriving agricultural, mining, and commercial center in the colonial period. The Bajío also was the birthplace of the agrarian unrest and revolt that fueled the Mexican independence movement. The social bases of this violence have been investigated elsewhere.⁴ But the way in which people in the region conceptualized, were affected by, and responded to changes in water availability, extreme weather, and disaster within a context of resource inequality, agrarian dissent, and social unrest remains to be explored in detail. Third, because of the region's economic, social, and political importance during the colonial period, there are particularly rich archival records available with which to investigate this theme.

Because Guanajuato was a scene of agrarian unrest, our work provides new insights into the history of agrarian insurgency in colonial Mexico. The historical literature makes clear the importance of considering cultural and structural factors and of incorporating analyses of the actions, powers, and adaptations of elites, states, and the agrarian masses.⁵ The significance of environmental change and climatic parameters as "triggers" of social unrest and change also has been highlighted.⁶ Less explored is the degree to which divergent "environmental knowledges" between social groups might have helped fuel and frame class struggles and agrarian unrest. Moreover, as Riley has recently illustrated, the literature regarding interactions between social strata in colonial Mexico, specifically Indian and Hispanic groups, has concentrated almost exclusively on conflicts over distribution and use of natural resources and labor demands, although shared environmental concerns actually may have transcended differential power relationships.⁷ This article suggests that intensification of class conflict was not the only result of drought and flood. In some cases, these events stimulated cooperation among different social groups.

Data Sources and Methodology

HISTORICAL RECORDS charting the effects of extreme events, coping strategies, technological adaptation, regulation, and recovery, long have been recognized as valuable sources for investigating how people have perceived, been affected by, and reacted to a variety of environmental changes. Travel accounts and descriptions, legal documents, crop and tax records, and maps, paintings and images, for example, all have been used to identify the timing of anomalous weather and extreme events and to chart their effects and societal responses to them.⁸

The rich colonial archives of Mexico have presented similar opportunities. While these sources have been used to investigate the demographic changes of the pre- and post-Conquest period, adjustments in land tenure and agricultural dynamics since the Conquest, there is now also a large corpus of work that illustrates how these sources can provide invaluable insight into the environmental histories of different regions of the country.⁹ A number of regional archival investigations, for example, have highlighted the different document groups (ramos) and historical sources that can be employed to reconstruct micro-scale environmental characteristics and to identify the environmental effects of post-Conquest changes in land use and tenure.¹⁰ Other investigations have used these sources to explore the relationship between agricultural and economic crises and periods of drought, and to investigate the connection between water shortage and conflict over water access and water rights.¹¹ More recent research has demonstrated the potential of these colonial documents for reconstructing climatic chronologies and for investigating the effects of and responses to extreme weather events in different regions of the country over the last six centuries.¹²

Various archival sources and documents in the Archivo General de la Nación (AGN) were consulted for this investigation. The most useful ramo was the Tierras, a collection of colonial litigation documents dealing with disputes over land and water (Pleitos). These documents were used to trace dissent over water and to investigate cases of water scarcity, deprivation, monopolization, theft, and flood damage. Changes in land and resource use were investigated through viceregal land grant (Mercedes) documents, while the Indio register, dealing with post-conquest socio-economic issues and public works, provided information on how local authorities coped with changing environmental circumstances. The ramo Historia, compiled at the close of the eighteenth century, was useful for eliciting period-specific social, demographic, and economic information for the various regions. These documents also contain details of crop blights, disease epidemics, and agricultural crises, occasionally detailing a climatic cause. Tributos (tax records) and Alhóndigas (records of harvests) were used to reconstruct variations in taxable crop yields and harvest losses due to market fluctuations and/or climatic vagary, while other ramos, including Rios y Acequias and Caminos y Calzadas provided specific information on infrastructural damage and repairs following heavy rainfall and floods.

Regional and municipal archival repositories and a number of private collections also were investigated. Several ramos were consulted in the Archivo Historico Municipal de Leon, in the city of Leon, Guanajuato, including the ramos Communicaciones, Aguapecuarias, Demandas, Aguas and Notorias. Work in the Archivo Historico del Estado de Guanajuato focused on the Actas de Cabildo, Aguas, Ayuntamiento, and Communicaciones. A number of documents copied onto microfilm and held at the Archivo Histórico in the Museo Nacional de Antropología, Mexico City, also were investigated. These included papers from the Eulalia Guzman collection, the Gomez de Orosco collection, the Paso y Troncoso Collection together with copies of documents now housed in the Casa Morelos, Michoacán, and in the Archivo Judicial de Querétaro.¹³ This archival material was supplemented with information drawn from various published missionary journals, historical travel accounts, and scientific reports.¹⁴

There are, of course, a number of problems with using archival sources for reconstructing environmental history and for investigating the effects and perceptions of extreme events. As primary sources written by individuals from a particular perspective and for a specific intended audience, the colonial records used in this investigation, for example, contain both intentional and unintentional biases. There may have been instances where there was deliberate sensationalism of the impact of particular floods or droughts in order to secure financial aid or tax relief or to challenge existing rights of access to water rights. There is no uniform definition of what constitutes a flood or a drought. There is no threshold or baseline data, so it is difficult to establish from archival sources what was perceived to be normal and what was considered to be unusual or extreme by different groups of people. Unusual events are judged against what was perceived to be a normal range of variations, which itself is a function of the nature and span of an individual's experience and the average range of variation communicated through oral histories or historical knowledge.¹⁵ There are opportunities to over- and under-estimate floods or drought. A late rainy season, for example, might be reported as drought in some circumstances, even though normal seasonal rains might arrive after the document was compiled. Early rains might be similarly misinterpreted as an unusual or extreme rainfall event, especially where this meant the flash flooding of ephemeral rivers. Descriptions of flooding of a bank-full river at the close of the season, from a contemporary stance at least, could be misinterpreted as a result of unusually heavy rains or an extreme rainfall, though this might be the normal status of the river at this time. Relatively normal weather conditions thus can be misinterpreted as unusual or extreme. Interpreting these sources unavoidably involves arbitrariness and subjectivity, and, as a result, myriad opportunities for error in the identification and recording of extreme events and their effects.¹⁶ Moreover, the archives provide at best only a partial record of past events. If the events resulted in limited human impact and economic loss, they may have gone unrecorded. There also may have been periods when events themselves disrupted in the administrative systems responsible for record keeping, leaving a gap in the record for a period when data is most needed.¹⁷ For all these reasons, archival investigations of drought and flood inevitably will be subject to error. Nonetheless, as expressions of contemporary environmental awareness and perception, these documents offer a unique insight.

Water and Vulnerability in Colonial Guanajuato

GUANAJUATO LIES IN the Bajío region in the north of the central Mexican highlands. The area has a semi-arid climate with a marked pattern of seasonal rainfall. Annual precipitation is about 650mm per annum, falling between May and October, mostly in afternoon thunderstorms. The region nearly always suffers a period of water stress in the hot, dry spring. There are considerable variations both in the intensity and incidence of the summer rains, occasionally resulting in severe droughts. It also has spatial variations in seasonal rainfall, with the more southern areas receiving slightly more rainfall than central locations.¹⁸ A number of important rivers flow in the area. The Lerma is the most significant. It rises in the Valley of Toluca and enters the Bajío region at Acambaro and flows onto Salvatierra and Salamanca. The Rio Laja originates in a basin north of San Miguel de Allende. The volume of flow in the Laja is a direct function of the amount of rainfall, but the river also is fed by a few modest springs, and so has a perennial flow. In addition, many ephemeral rivers form in the hills surrounding the plains of the Bajío during the summer rainy season when water runs off the hills into a series of small stream and arroyos.¹⁹

Although settled by sedentary populations from the Pre-Classic era (c 2500 BP), by the time of European contact, the region was occupied only by dispersed, semi-nomadic tribes, collectively referred to as the Chichimecas.²⁰ Any permanent indigenous settlement and land use was restricted to the southern periphery of the Bajío around Penjamo and Acambaro. In the early years of the colony, a few encomiendas (grants of indio town or towns, carrying the right to assess tribute) were awarded in the region, mainly in the more fertile southern areas of Apaseo, Yuriria, and Acambaro but the main stimulus to colonize the area came with the discovery of silver, first north of the region in Zacatecas, and later in the mountains of Guanajuato. While the discovery of minerals was the main stimulus to colonization, the town was the main instrument. A series of garrison towns initially were established to safeguard the first settlers from Chichimec attacks and to protect the passage of mineral wealth through the area. Thus, San Miguel el Grande was established in 1555, San Felipe in 1562, Santa Fe de Guanajuato in 1554, and Leon, later the capital of Guanajuato, in 1576.²¹ Spanish colonization attracted a substantial migration of Purépecha and Otomi indios from the south and east, especially to the more southerly districts surrounding Celaya. But not all migrants relocated voluntarily. Repartimiento or forced indio labor from pueblos in Michoacán, for example, were assigned to some of the first residents of new towns to assist in the building of houses and public works in the area.²² Labor drafting appears to have continued throughout the second half of the sixteenth century, judging by claims forwarded by indios at the turn of the century that this was leaving their own pueblos "almost depopulated."²³

Map 1. Bajío Region in Mexico.

Map courtesy of Chris Lewis.

To attract settlers to the region, the Crown awarded land to each town for distribution among its new residents, each citizen being entitled to 2.5 caballerías (a unit of agricultural land equivalent to 265 acres). The colonial authorities encouraged Spanish and indigenous settlement in the area with incentives of formal viceregal land grants (mercedes reales) awarded by the Crown. Mercedes for estancias, for cattle (ganado major) and sheep (ganado menor) began to be awarded in the 1550s.²⁴ Some estancias were awarded in conjunction with small plots of agricultural land, though mercedes solely intended for agricultural land (caballerías de tierra) also were awarded.²⁵ Records indicate that the number of both agricultural and livestock awards began to increase in the 1560s and 1570s. The number and type of mercedes that were awarded in different parts of the region varied. It should be noted that these records do not necessarily represent a true picture of the nature of land-use changes, in that conferment of a grant did not always mean that the land in question came into use immediately. In the early years of colonization of the area, frequent Chichimec raids were a deterrent to permanent settlement. Moreover, land often came into use that was not formally negotiated though the legal merced system. Nonetheless, some general trends in land-use change have been identified through the land-grant records. Celaya, for example, was founded in 1571 to encourage agricultural development of the region as a whole. By 1591, an estimated 153 awards of agricultural land had been granted in the vicinity of the town.²⁶ Awards for cattle estancias were made in Salamanca, where by 1591 an estimated 41 estancias had been formally approved. Thirty-two cattle ranches had been granted in the vicinity of Guanajuato by this time. Sheep also were raised in the region, specifically in the vicinity of San Miguel. After 1591, and perhaps reflecting the Crown's livestock marginalization policies of the period, cattle were marginalized to more western regions, though in greatly reduced numbers, while sheep trans humance expanded northward.²⁷ After the 1630s, the awards of mercedes for land and livestock ranches decreased notably.²⁸ Though mercedes still were being awarded, they were only occasionally for livestock or agriculture and were more commonly for specific purposes, particularly for water for milling or irrigation.²⁹ The awards that were made between the 1550s and the 1630s are thought to have been most influential in determining the nature and form of the region's agrarian development for the remainder of the colonial period. As with other parts of the colony, it is thought that amalgamation of mercedes in the late sixteenth and early seventeenth centuries facilitated the emergence of large estates or haciendas, a process that has been investigated elsewhere.³⁰

Water was essential for cereal production. Maize flourished in this environment, but the preferred cereal crop, wheat, which the Spanish introduced, required irrigation to survive the dry winter months. Irrigation also made fields in the region much more productive.³¹ Livestock raising, too, was dependent upon a regular supply of water, and the new towns and cities of the region required the provision of a steady supply of potable water. To ensure access to water supplies, the key towns were located along major rivers, and many of the first land grants for livestock or agriculture were awarded alongside rivers and streams and near springs.³² Permanent and ephemeral watercourses, rivers, and arroyos all were exploited, and groundwater was tapped in many locations, though perhaps more so in the later colonial period.³³ In general, control of water followed control of land. Examples of direct acquisition of water rights are few and the amount of water affected was small. In Celaya in the 1570s, however, nine of the twelve grants awarded to residents of the new town included a right to access water on certain days. This trend in allocating water rights appears to have been less common after 1600.³⁴ People made extensive use of water storage, diversion, and water management systems. Storage of floodwater, for example, for use during the dry season, a strategy referred to in the documentation as medio riego, is thought to have been in practice in the late sixteenth century.³⁵ The scale of water management in the region, however, expanded significantly in the eighteenth century.³⁶ Many earthen and brick dams, canals, and reservoirs were constructed and water was diverted from key rivers in the region, such as the Rio Laja and the Lerma, to irrigate wheat fields or to provide water for towns.

Population expanded rapidly throughout the colonial period, but especially in the eighteenth century. In 1742, the intendencia of Guanajuato supported 156,140 people. (New Spain was divided into 12 intendencias, or states. The boundaries of colonial Guanajuato were approximately those of the modern state.) By 1793, the population had risen to 397,942, and there are estimates of a population of about 513,300 just after the turn of the nineteenth century.³⁷ This population expansion and the availability of land in the region stimulated an increase in cultivated acreage in the late seventeenth century and throughout the eighteenth century. Indeed, the economy shifted further away from livestock ranching to agricultural production. The production of cereals increased across the region, accounting for approximately 45 percent of total tithe value by the late eighteenth century.³⁸ The economy of Guanajuato, and the Bajío as a whole, became relatively prosperous based on agricultural production, mining, industry, trade, and, to a lesser extent, stock-raising. So rapid was the rise of economic development that one scholar of the region has referred to it as the "pace maker of the colonial Mexican economy."³⁹

By the second half of the eighteenth century, the region was characterized by a distinct class divide. The vast majority of rural residents lived as estate dependants, while the Spanish regime allowed the provincial gentry to monopolize the best land and water sources. The combined effect of population growth and commercial expansion after 1750 brought additional problems. Economic growth was led by the export-oriented mining sector, favoring only a minority of Mexicans. The estates in the Bajío began to concentrate on producing wheat, fruits, and vegetables that could be sold for high prices, while farmers lost interest in maize production—the staple of the poorer sectors of society. Seasonably variable rainfall also was a constant threat to agrarian livelihoods and affected the economic well-being of the region in general. Variations in both the intensity and incidence of summer rain and occasional extreme weather events periodically threatened harvests with profound implications for this water-dependent colonial society.⁴⁰ The archives include reports of at least nine years of severe drought-induced hardship in the region and isolated references to drought from other localities between 1600 and 1800.⁴¹ The combined droughts and frosts of the early to mid-1780s that culminated in widespread harvest failure and starvation in the "year of great hunger" between 1785 and 1786 led to a subsistence crisis among the rural poor of the region. This heightened the growing recognition of inequality and injustice helped fuel agrarian unrest in the second half of the eighteenth century.⁴² Intense rainstorms and dramatic floods also caused economic dislocation and death on many occasions.⁴³

Water Manipulation and Power Relationships

COMPARISON OF A number of different archival sources suggests that drought affected harvests in Guanajuato and the Bajío region in 1590–1591, 1601, 1641, 1647, 1651, 1662, 1696, 1751, 1778, 1780, 1784–1786, 1793, 1803, and 1809, resulting in harvest loss and, in the case of 1651, 1751, and 1784–1786, drought caused widespread hunger and famine. Given the propensity to drought, water was a highly contentious issue. Periods of drought exacerbated the competition to secure access to water and confirm water rights.⁴⁴ To some extent, expectation of drought and an acute awareness of vulnerability to fluctuations in rainfall in Guanajuato are manifest in the many and varied lawsuits concerned with water monopolization, deprivation, usurpation, and over-use.⁴⁵ Many of the cases, which date to the first stages of colonization and settlement, dealt with complaints about illegal diversion of water and the implications this had for crops reliant on irrigation water. In Celaya in 1573, for instance, complaints were made about Don Juan de Yllanes, who was diverting more than a half of the water from the Rio Laja for the benefit of his lands and those of Ponce de Leon, and depriving the local residents of the town of much-needed irrigation water for their own plots. The commissioner responsible for land administration in the region resolved to confiscate some of Yllanes' land and declared that both Yllanes and Ponce were prohibited from irrigating their fields until the residents of the town had first irrigated theirs.⁴⁶ Similarly, a number of lawsuits describe instances of water "theft." One document filed in 1634 details a dispute between the residents of Celaya, the council, and a group of local hacendados who were being charged with extracting and "stealing" water from the river to irrigate their wheat fields. According to a number of witnesses, "the river no longer contained water" as a result of the illegal actions of hacendados upstream.⁴⁷

Cases detailing perceived injustice over water distribution were filed frequently. One long-running dispute between the naturales of San Miguel and the Spanish residents of a settlement referred to as the Villa de Españoles, focused on the use and misuse of a spring of water known as El Chorillo (ironically meaning "the constant stream"). The lawsuit spanned close to a century between 1655 and 1745. In papers filed in 1745, the naturales (indigenous residents) of the town suggested that "the water which originates within the town has been demarcated half to the town and the other half to the Villa de Españoles." The problem had arisen "because it was found that almost all the water is channeled to the villa, leaving such a small amount flowing that not only do they [the naturales] suffer the loss of their sown crops but they have a lack of water provision necessary for the people." According to colonial Mexican water law, water rights held communally by indigenous communities were defined by the needs of that community. The needs of these indigenous people apparently had not been met. They were consequently left in a "miserable" state and so requested a fairer, legal division of the waters. Investigations at the time revealed that not all houses and residents had equal water allocations and this lack of equitable division was causing "much violence and leaving some with nothing and letting others take as much as they want."⁴⁸

Threats of water scarcity and actual water deprivation in this drought-prone region appear to have driven many legal disputes. In some cases, however, communities seem to have cooperated in devising a system of water sharing in order to hedge against the problems of scarcity during periods of drought or late rains. A drought in the Valle de Santiago in the summer of 1780, for instance, appears to have stimulated a degree of cooperation between local water users and the Augustinians in the area. In this case, it involved investment in a new canal to drain the water from Lake Yuriria for use by the local communities in the valley as well as the Augustinians who invested heavily in the construction works.⁴⁹ Some moves toward maximizing water efficiency appear to have been made. Water recycling strategies occasionally were adopted in order to resolve differences between conflicting users while at the same time maximizing water use. A dispute from 1614, for example, was concerned with the sharing of remanente water (literally meaning surplus water) between the indigenous residents of Acambaro who required it for irrigation and Francisco de Villadiego Senderos, who required water to run his mill. Senderos charged that the promise of the residents to leave him a quantity of water to power his mill had not been honored. Both parties finally agreed that first the water should be used in the mill and that the used water then would irrigate the fields. That way, the situation where all the water was used before it ever reached the mill could be avoided.⁵⁰

Severe droughts exacerbated problems of water sharing and rationing. During the drought in central Mexico between 1590 and 1591, Don Luis de Velasco Avasolo Perez de Bocanegra, Alcade Mayor of Celaya, was asked to support the naturales of the town in their claim that they had suffered "common damages and disputes" over water because of the actions of a number of Spaniards who had agricultural lands and ranches in the area.⁵¹ Similarly, the drought of 1696 resulted in a number of additional problems, incuding a dispute about sharing a much reduced supply of water for irrigation. In that year the residents of the town of San Juan Bautista de Apaseo battled Juan Garcia de Alarcon over water access. The residents had a concession to "half of the water to irrigate their fields" but this, they argued, apparently was being threatened by the actions of their neighbor, Alarcon, who they charged with "irrigating a great part of his lands in a year so calamitous as the one currently being experienced."⁵² The droughts that contributed to the well-documented "Year of Great Hunger" in 1785–1786 also seem to have had stimulated water disputes. One document from 1785 charts negotiations between Juan Bacilio, resident of San Andres Apaseo and Don Joaquin Fuentes, the administrator of the haciendas belonging to Captain Don Juan Antonio Fernandez de Xauregui, local councilor of the city of Querétaro. The administrator accused Bacilio of "modifying the course of water from its original route for twenty days and leaving none to pass to their destinations in the haciendas."⁵³

As in other regions, access to water and the securing of water rights were highly contentious issues in the Bajío, particularly in the eighteenth century.⁵⁴ Both actual and feared water scarcities drove legal disputes and contributed to conflicts over water between all sections of society. Drought heightened the competition for increasingly scarce supplies and frequently was cited as legal evidence in many of the lawsuits over water rights and deprivation. Virginia Garcia-Acosta has suggested that as knowledge about drought and its effects improves, more droughts are recognized, recorded, and remembered.⁵⁵ It is possible, therefore, that by the late seventeenth and eighteenth centuries, public knowledge and experience of the effects of drought were greater and may have been used as a manipulative tool in at least some disputes. To some extent, the contention over water in the later seventeenth and eighteenth centuries reflected a more general dissent and the growing awareness of power differentials and inequality over resource access and distribution, particularly in the second half of the eighteenth century. There were some instances of cooperation over water and agreements for water sharing between different groups, though these cases may have been the exception rather than the rule. Yet even legal arrangements conferring water rights or access appear to have been flaunted and actually may have exacerbated problems of water sharing in the region.

Water Management and Flood Risk

RIVERS WERE both an asset and a threat in colonial Guanajuato. They provided water for irrigation and domestic purposes and the fertile alluvial soils of the floodplains were prized for agriculture. The destruction wrought by sudden, violent, and uncontrollable flooding, however, was recognized as a recurrent problem for riverine communities, landowners, and businesses. In the archives, only a small number of records directly linked unusual extreme rainfall to flooding. The majority of floods, in contrast, were perceived to be a function of the local geography or a result of human manipulation of the water supply: By the eighteenth century, the region had a complex myriad of water diversion channels, dams, and reservoirs.

Literally hundreds of floods are recorded in the archives of Guanajuato and the records show that people were aware of the risks that the rivers posed. The Rio Laja, for example, was considered to be "one of the most heavy flowing rivers of the whole of the Americas," a claim borne out by the fact that "its terrifying waters caused infinite numbers of deaths occasioned by its very many floods."⁵⁶ Flooding as a result "of the tempestuous flow of the river which runs through the middle of the city" of Guanajuato also presented a frequent problem.⁵⁷

Various documents chart the perceived causes and effects of these events. Some locations were recognized as particularly vulnerable to flooding by reason of their physical location. One observer suggested in 1788 that flooding in Guanajuato was a function of the city's surrounding geography: "The waters of the rains were channelled/combined by the steep slopes and arid terrain ... and they [the people] fear their falling waters and often they occasion significant damage and loss, and that the most sensitive and saddening events have been seen in the last few years when the waters have increased and pour down from the hills to the east and south and bathe the city."⁵⁸

Particular buildings affected by flooding were seen to be at risk because of their location. In a document dated July 1637, Brother Pedro Guitierrez Gaton, Prior of the hospital-convent of Espiritu Santo in the Villa de Leon, noted that "there was a flood in the river which passes alongside our convent and which took away a great part of it." A series of impartial witnesses provided evidence to suggest that this was not a rare event: "The convent was founded twenty years before over which time, the hospital had seen the river flood on three or four occasions ... the waters rose, leaving the main channel and inundating the rooms/ chambers and patios of the convent and also the church."

Another witness indicated that the problem was directly associated with the location of the hospital relative to the river: "The hospital de Jesus had suffered much damage because it was located lower than the rest of the buildings ... it had survived other flood events, one in the middle of the night, that was so big that it posed a threat to many people." This witness, a wealthy resident, apparently had firsthand experience of the flood. He had been involved, along with his servants, in the rescue some of the more infirm in the hospital, taking them to higher ground. He indicated that the hospital was located in a high-risk area.⁵⁹

No mention was made of any unusually heavy rains initiating the flood. In a small number of cases, however, people described floods as being a result of extreme rainfall. The flood that inundated the city of Celaya on 28 June 1692 was attributed by the contemporary writer and commentator Lucio Marmolejo to heavy and incessant rains "which had not ceased to fall since the last hours of the afternoon." The "torrential rainstorms" caused the river to flood just after ten o'clock at night and there ensued: "terrible panic among all the inhabitants of the city, but with the darkness of the night no one knew where the most danger lay and much less how to escape this ... men, women and children were desperately shouting and crying ... and the turbulent waters invaded everything with impetuous force ... no one believed there was any possible escape from this and all began begging for mercy."

The effects of the flood were devastating and far-reaching. The whole city, "was left like an immense field covered in mud, uprooted trees and branches, rubbish, debris, bodies of all kinds of animals and ultimately, all the other remnants of the near destruction.... The groups of voluntary helpers and the troops of the leading regiments ... began the work of removing the rubbish and debris in search of victims of the flood and the residents who had died in their houses. Close to three thousand families lost their houses and livelihoods: the sown fields were destroyed and were also devastated in many of the surrounding places."

The flood was not the only catastrophe in 1692. Marmolejo suggested that "the year is memorable for the suffering from the great scarcity of provisions in the majority of the country, the cause being the loss of almost all the harvests the year before."⁶⁰ The scale of scarcity caused grain riots elsewhere in Mexico.⁶¹ Famine, disease in epidemic proportions, and unrest also gripped the Bajío region, causing massive life loss, especially among the indigenous populations.⁶² The flood of 1692 thus seems to have exacerbated more widespread problems and to have compounded the difficulties faced particularly by the rural poor. The situation became untenable and the crisis that followed culminated "in the emergence of popular uprisings in Guanajuato ... and among other populations."⁶³ In this context, the flood in Guanajuato may have gained a more significant position in the historical record because of the calamitous nature of this year in general.

Descriptions of a flood in Guanajuato in 1770, recorded as part of a survey of damages conducted by a local administrator, indicated that its origins lay in similarly heavy and unusual rainfall. "According to word of mouth" one source suggested, "there was a very heavy rainstorm in the hills and in the city, causing a great flood in the arroyo or small channel which crosses many parts of the city." A reconnaissance trip revealed that there were other exacerbating factors: "I went out to look at the whole city and its surroundings to ascertain the damage ... the cause of the ruin lay in various dams and reservoirs made in the river channel, the various pillars with foundations belonging to the haciendas with which the hacendados procure the commodities of the said arroyo, trapping the waters."⁶⁴

The description indicates that water storage systems in the city had exacerbated flood risk and the collapse of a dam seems to have been the main cause of this particular flood event. Dam breaches like this were commonplace and in most instances related to poor maintenance or neglect. Nonetheless, in this case we also must consider that the "very heavy rainstorm" may have been influential in triggering the breach.

A document recorded in Celaya on 26 June 1791 by the mayor of the indigenous residents of the city illustrates a similar problem. He suggested that "there has been seen twice an overflowing of flood waters which afterwards have caused ruin and damage in the houses and greater damage for the general public," adding that: "The Laja had destroyed our maize plots and the rest of the sown fields, indications are that the floods have completely destroyed our houses and we have been put in imminent danger."

The cause, it seems, rested with the local hacendados or estate owners who had changed the natural course of the river with dams "causing damage in times of floods." The indigenous community thus drew a direct link between the imposition of dams and flood risk, for, as the mayor suggested, "the water only has only to tip slightly over the top of the dam ... a large stretch of territory on one and other side of the land can be effectively drowned in the floods." People had a clear awareness of the environmental, social, and economic risks posed by water diversion and storage in the area, which seems to have been based on past experience of flooding.

Seeking some level of intervention from the local council, the mayor referred to the action taken following a flood on August 7 the previous year, which he described as "one of the greatest floods that there has been in this city." The scale of the inundation and the damage inflicted led the local council to decide that "all dams should be drained to prevent the floods which have caused local residents to suffer with notable damage to the health and their interests"—a course of action that they felt was justified given that one of the dams apparently had been "constructed furtively and almost with some degree of despotism." The year had been perhaps unusually wet, and the river itself was described as "tempestuous and turbulent." Nonetheless, the council perceived that water storage behind the dams had exacerbated the flood risk.⁶⁵

The council's decision to dismantle sections of the water system was controversial. Several lawsuits illustrate the degree of unrest voiced by local landowners. One dispute between Captain Crespo, hacendado of Molino Chico in Celaya, and the council called in a large number of witnesses, chosen specifically because of their "advanced years" and their consequent ability to draw on personal experience and historical knowledge of water management and previous flooding in the area. Witnesses "two, six, eight and twelve" suggested that the cause of the floods were the intakes and dam that had been built. The remaining witnesses argued that the small river channel, the poor condition of the river banks and flood walls, and the river's geographical dominance in the city were more to blame. Indeed, if anything, they argued that the water systems were quite useful in that they "abstracted water from the general flow of the river, and further argued that "before they were there, the river had more power."⁶⁶ Evidence drawn from personal experience and social memory of severe and recurrent flooding thus suggested that flooding had been a persistent problem for some time. While communities affected by flooding argued that the manipulation of water from the river and the damming of the channel by local hacendados had increased the flood hazard, the hacendados themselves, together with a series of supposedly impartial witnesses, suggested that the water management had, if anything, lessened flooding.

To resolve the differences, the local council employed Jose Mariano Orinuela, described in the document as an "expert" in this field of flood risk, to survey the problem and review the evidence. He concluded: "There is no doubt that works ... to extract or deter the waters of the river should be undertaken only with special precautions especially when there are populations located nearby. Drainage or irrigation channels crack the ground immoderately where they pass, bringing much material which is discharged into the channels and flows down ... inundating the sown plots of land, houses and roads: the dams and reservoirs collect deposits of sand and mud that they leave on the bed of the river reducing its capacity and in times of high water, causing the water to pour out across the margins of the river banks causing damage to the neighboring lands."⁶⁷ Expert opinion supported the case made by the indigenous community, though sedimentation was highlighted as a key problem.

Some floods seem to have been used as historical benchmarks against which the effects of other floods were measured. A document from 1804 charted a "grave flood that took place" in Guanajuato during the rainy season of that year when the river Lerma was "higher than the roads and in the houses." The 1804 flood apparently caused "equal or greater suffering than others" and was contrasted with the flood of 5 July 1760, which "resulted in turmoil ... causing the disaster to survive in lamentable tradition as one of the most memorable that has been experienced." Occurring "at twelve at night and finding the river without a bridge or any flood defences ... the houses were flooded with water, the roads were covered and there were innumerable people drowned or unspeakably injured." Travelling priest Fransisco de Ajofrín was in Guanajuato in 1760 when the flood took place, and his firsthand description indicated that the event may have been triggered by a storm: "The city experienced great destruction of the houses, haciendas and among the people because of a furious thunder storm which caused a sudden burst of water in the nearby areas, (a phenomenon they call here 'snakes of water') which caused an astonishing increase in the river and the ruination of houses, drowned people, destroyed water falls and caused an infinite amount of damage." Ajofrín also reported "many flashes of lightening, though these were not dangerous."⁶⁸ The event led the affected communities to address structural issues: "Various bridges were built, they build up many fences, the foundations of the houses and haciendas were re-enforced, and also these and the streets were raised with the same materials as were drawn from the river." These adaptations seem to have been partially successful as "twelve years later in 1772 there took place another flood ... although it caused fewer damages because of the actions and precautions adopted in the previous flood." This event was followed on 27 July 1780 by a flood apparently "greater than that of 1772, but less than that of 1760 in its effects because the river channel was not without some guard/defence ... this inundation, although big, did not cause any precise damage."⁶⁹ Nonetheless, the impact of floods appears to have been reduced, but the frequency of flooding in this area clearly presented a problem.

Although extreme or unusually heavy rainfall and the start of a normal rainy season no doubt contributed some floods, people in Guanajuato generally perceived the problem of flooding as a function of the geography of the area and the imposition of water storage and management structures. To some extent, the predominantly anthropogenic explanations of flooding may reflect a general awareness of the power relationships between different social sectors of the population and of the different levels of social vulnerability to drought and flooding. Local communities were keenly aware of their water rights and frequently contested them. By challenging neighboring land owners' use or misuse of water sources, or by charging them with damages resulting from the neglect of dams, fines could be levied and water rights modified. Experts employed to investigate the cause of flooding generally supported the suggestion that the water infrastructure was a key problem, though local knowledge of historical flooding seems to have gained legitimacy only when corroborated by "expert" opinion.

A cluster of recorded floods occurred in the second half of the eighteenth century. Most of the descriptions offered by local residents and administrators once again imply that these floods related more to water manipulation, diversion, and storage in the area than to other factors. This was a time when the development of complex irrigation networks, dikes, and water-storage systems in the area reached their zenith. Geomorphological research in the Bajío has revealed evidence indicating an increase in floods in real terms in the second half of the eighteenth century and supporting the suggestion that these floods had predominantly anthropogenic causes. As with other regions of central Mexico, population expansion in the eighteenth century increased pressure on resources in the region and contributed to an intensification of land use and to the clearance of vegetation to bring more land into agricultural use.⁷⁰ The increase in soil erosion that Metcalfe et al. and Endfield and O'Hara have identified in the region in the second half of the eighteenth century could be directly associated with this period of agricultural intensification and expansion.⁷¹ It could be, then, that the increase in flooding at this time was a response to population pressure, vegetation clearance, soil erosion, accelerated run off and higher peak flood discharge. Mining activities also may have contributed to flooding. Indeed, Butzer and Butzer think that the devastating 1760 flood event in Guanajuato may have been associated with "intense mining disturbance around that city," though contemporary commentators indicated that a severe storm event may have acted as something of a catalyst to this flood.⁷²

Flood Alleviation and Management

SOME OF THE high-impact floods remain prominent in the social memory, and are used as historical reference points against which the effects of other floods are compared. Such events became inscribed into the memory of communities through adaptation, response, and recovery. Indeed, the scale of the losses incurred suggested by some of the more dramatic floods stimulated a range of immediate responses and coping strategies as well as longer-term flood alleviation and remediation schemes.

One of the most immediate concerns following floods was the need to restore communication and trading links as quickly as possible. In response to the "fatal flooding" of Guanajuato in the 1770s and 1780s, which "broke the bridges and the fences, the river taking a precipitous course to the centre of the city," the local council took measures to "re-construct from new, the bridges that were destroyed and at the same time the fences/walls, both of which are necessary things."⁷³ Yet a document compiled twenty-four years later suggested that the effort was only partially successful, for there remained an "urgent need to build a bridge ... and to make two big pillars to give direction to the waters and to avoid the floods which this city has experienced."⁷⁴ Trading relationships elsewhere in the region were similarly disrupted by flooding. A request for a license "sought to build a bridge on the Turbio River in the jurisdiction of the Villa de Leon for the benefit of the residents" in 1784 represents one response to the loss of earnings caused by this recurrent problem.⁷⁵ Similarly, documents compiled between 1799 and 1803 detailed similar measures adopted on the Rio Laja. Because it was necessary to cross the river to trade with the surrounding region, it was resolved "that the bridge should be made more solid, the cost of the construction being 13,000 pesos." A complementary flood alleviation plan also was to be implemented involving the construction of a series of "steps/terraces ... to contain the sediments and other materials that could not pass through the eye of the bridge."⁷⁶

Flash flooding after periods of drought or at the end of the dry season also was recognized as a potential problem. Paradoxically, concern over the prolonged drought in the mid-1780s seems to have prompted the development of anticipatory flood alleviation projects. One document charted the need to rebuild the bridge known as Granaditas de Salgado in Guanajuato for fear that the "river will be intransitable in the next rains because the waters coming off the mountains will be copious." Residents feared that the onset of the rainy season after such a prolonged dry period would lead to massive erosion of material from the slopes into the river, increasing the risk of flooding. Thus the bridge "was not only considered useful, but necessary" to avoid the anticipated flash flooding that could ensue.⁷⁷

People also recognized that the accumulation of sediment and debris in river channels and behind dams designed to store water significantly raised the risk of flooding. Dredging and clearing, therefore, were among the more common flood prevention techniques: Several documents refer to the need to clear the rivers of sediment and debris in order to reduce the risk of flooding. Individual landowners were responsible for ensuring the steady flow of waters that passed through their lands and were charged with clearing their own stretches of the river.⁷⁸ But there were also larger community- and city-based clearance projects that involved much more participation by all sectors of society. Dramatic flooding in Guanajuato in 1749 led to the development of one such dredging project, devised and forwarded by local residents and land users, particularly those living in one street, Calle de Alonso, who regarded themselves as "being in great danger." They suggested the main cause of the problem lay in the "rubbish and waste of the city and the material from the hills and mine works" which were being dumped or washed into the river. It seems there had been previous efforts to clear the river of such debris, but these had not been maintained. The local residents also proposed additional measures to prevent flooding, which included the construction of flood defenses in the areas that previously had been flooded and an ambitious plan to reduce the steep nature of the ravines and gullies surrounding the area to reduce the likelihood of material being washed into the river. Other proposals included diverting some of the water from the channel with a series of dikes or reducing its power through a number of small waterfalls. In response to, or perhaps as a reaction to this rather proactive community, the local administration once again enlisted a group of apparent experts for their opinion on the problem. These experts produced a map that showed where debris had built up and which were most in need of clearing. One expert concluded that: "It was obvious that the river had been cleared in the past but ... it was necessary that this should be done every year and to save the 5000 peso cost for this procedure, it would be simpler to ask residents to not throw their rubbish and waste into the river."⁷⁹ Expert opinion thus supported the need for regular dredging but raised the thorny issue of the costs for such a continuous and high-maintenance endeavor and effectively attributed the cause of flooding, and by extension efforts geared towards flood-risk reduction, to the local community.

High impact "benchmark" events stimulated much more ambitious and organized structural flood alleviation programs. Following the dramatic flood on the Laja in 1692, a cross-section of representatives of the city undertook a survey of the local river systems "with the objective of ... developing measures to conduct water to avoid new floods," finally deciding that "the only way to avoid flooding was the construction of a dam above the river ... to contain the waters that come down from the hills and to release this water, little by little into small storage areas, forming in this way a controlled water flow, so reducing the danger of large floods which have proved so dangerous for the city." The undertaking was heavily dependent upon the good nature, or perhaps shared grievance of residents and landowners of the area, though the actual development and construction of the plan was influenced by class distinctions. While Spanish residents were requested to make financial contributions toward the cost of the project, for example, the indigenous residents were asked to provide support in the form of manual labor. People also recognized that the level of the river water had increased with the build up of silt at the confluence of the Laja and San Miguel rivers and a suggestion was made that the residents "would spend the whole of their lives cleaning out, year after year, the silts from this area to avoid blockages."⁸⁰ Judging by the number of later floods, the plan, although followed through to fruition, was only partially successful, largely because the local council failed to maintain the dam works.⁸¹

The documented floods that affected Guanajuato in 1760, 1772, and 1780 similarly resulted in large-scale flood response and alleviation projects. After the life and economic losses of the dramatic 1760 event, for example, the local council "resolved that it was important to build up a slag heap, as had been done in times past, to raise the level of the road and houses to a higher level to ensure that the river bed/stream bed is always lower than the level of the houses."⁸²

"Traditional" strategies were thus resorted to, but further measures also were suggested for the most vulnerable households, including "those residents that lived in Calle de Alonso." Given the disquiet that these residents had voiced following the devastating flood of 1749, it was resolved that flood warnings should be "given to the people who live there using a brief noise/signal indicating that they must leave the houses and close the doors of the houses." A list of the buildings perceived to be most at risk also was issued. Another measure promoted by the residents involved using some of the material dredged from the river to build a flood barrier. There was some objection to the proposals. Though some thought the use of a "slag heap" in this way was a good idea so long as it was properly and regularly maintained, some local landowners claimed that this proposal "would require the industry of a multitude of men to first clean the river from the point where it drains out." There also was concern among residents that such a flood barrier would allow pools of water to collect and stagnate and "this would infect the air, corrupting it and causing the residents to breathe this in." Aside from environmental health worries, the "insupportable costs" of the proposal were a problem. Other elements of the plan were implemented and appear to have been at least partially successful. Indeed, as mentioned above, the events in 1772 and 1780 caused significantly less damage. Nonetheless, it took twenty years and successive floods for the local administration to respond to the original complaints and proposals forwarded by the community in 1749. Moreover, community recommendations again were considered only when mediated and corroborated by "experts."

Following a flood in Guanajuato in 1788, residents had a well-grounded fear that "the arches of the bridges of the river" once again were posing a risk that would have an effect if "precautions are not taken." Yet again the local administration agreed "to clear the river, the eyes of the bridges and various channels and conduits ... so that even though the rains might be abundant, the waters will not leave the main channel."⁸³ This time, anticipating concerns from local landowners that the cost of the task might fall on them, the council suggested that the labor could be provided free of charge, "the offenders of the local prison bearing the cost of the work."⁸⁴ Similar schemes appear to have been proposed elsewhere in the region. In 1792, for example, the council asked the Real Hacienda for five hundred pesos "to pay for the clearing of a bank of sand that is in the river."⁸⁵ Other plans combined this tactic with more significant changes to local land-use planning. Repeated episodes of flooding in the town of Guanajuato had, by January 1805, resulted in a resolution to rebuild the main square, the Plaza de San Diego, effectively "raising it to avoid flooding." Nevertheless, it was suggested that the practice of "clearing of the river by hand" should continue.⁸⁶

Floods thus stimulated both reactionary and anticipatory responses at a range of levels, from the individual to the administrative. All sectors of society were affected by flooding and all were in some way involved in developing, financing, or implementing flood alleviation projects. People recognized the build up of debris in the river channels, behind dams, and around bridges to be a particular problem. Dredging and clearing were thus among the most common flood-management strategies. Large-scale flood alleviation projects were proposed and, in some cases, implemented, though the lack of maintenance of these works may have exacerbated flooding in the region. Perhaps most significantly, although there were some concerns over financing flood control, there appears to have been a high level of community participation in flood alleviation. Flood management and recovery appears to have engendered a degree of cooperation and collaboration between different sectors of society in the second half of the eighteenth century. Thus, while there was a rising awareness of social injustice and inequality in a context of emergent agrarian unrest, there is evidence that shared concerns over the environmental and social risks, potential damages, and losses to flooding actually transcended class divides and differences and provided something of a focus for community cohesion and cooperation.

Conclusion

WHILE SOCIAL and economic systems generally evolve to accommodate deviations from "normal" weather conditions, this is rarely true for extreme events, such as drought and flood. For this reason, such events have had dramatic and immediate environmental, social, and economic effects.⁸⁷ Inasmuch as extreme events pose a risk, however, they also have an orienting function. Knowledge of past events can condition how people comprehend and respond to uncertainties with respect to the timing and impact of events, can determine how people conceptualize risk and anticipate the impact of future events, and can be critical to the development of effective adaptation and response mechanisms. In this way, extreme or damaging events can become part of the fabric of thought, knowledge, discourse, and practice of a society or community as well as its infrastructure.⁸⁸

Archival documentation illustrates how different sectors of society perceived, conceptualized, and responded to changes in water availability and flooding and provides insight into how people used environmental and climatic knowledge and experience. Drought and water scarcity posed a constant threat to colonial society in Guanajuato and stimulated various responses. A number of scholars have investigated the landscape changes associated with the risk avoidance strategies of "traditional" agrarian societies in Mexico.⁸⁹ In Guanajuato, efforts to reduce vulnerability to variations in precipitation were geared primarily toward ensuring steady and regular water supply, specifically for irrigation, but also for domestic use and for livestock. Drought contingency planning also was built into water management legislation, and laws included clear restrictions on water use, rationing programs, conjunctive use of surface and ground water, watershed management, and recycling projects. In some instances, physical water scarcity fuelled cooperative water-sharing agreements and developments designed to improve water provision for vulnerable townships and institutions.

Experience and anticipation of drought-induced water scarcity also is evident in the legal disputes over water rights and access, particularly in the later seventeenth and eighteenth centuries. The majority of water-related lawsuits recorded in colonial Guanajuato chart the concern over water scarcity, theft, monopolization, illegal damming, or diversion and over-use. Research elsewhere in colonial central America has identified increasing unrest over access to land and other resources throughout the period.⁹⁰ Competition for resources and dissent over unequal resource distribution escalated in the 1700s, in a context of rising population and increasing monopolization of the best lands and resources by the emergent haciendas.⁹¹ Because of this population growth and the increased competition for natural resources, any analysis of the relationship between water conflicts and drought is questionable and has been dismissed by some scholars as "pointless."⁹² While drought certainly is cited in the disputes between water users in Guanajuato, only in a small number of cases can drought be verified. Rather, a fear of water deprivation or perhaps the memory of the effects of drought-induced scarcity—in a context of competition for water and dissent over poorly distributed land and water resources in general—underpinned many of the documented water disputes. In some cases, people also may have made opportunistic use of drought as a legal tool, with one or the other party highlighting drought, water deprivation, and scarcity in order to modify or secure water rights. An awareness of the propensity for drought in this region may have been employed in some litigation, highlighting at least a more indirect link between drought and water conflict.

Some scholars have questioned the effectiveness of such litigation as a means of securing water access. Legal battles were only one manifestation of the struggle over water access and water rights. Illegal diversions of water from streams and channels and deliberate sabotage of water diversion systems and dams may have been more commonly resorted to in cases of differential water access.⁹³

Neglect or deliberate sabotage of water management structures—designed to overcome the problems of drought and competition over scarce water supplies—exacerbated flood risk in the region. Only in a couple of instances was flooding directly linked to unusual or extreme rainfall or a storm. Residents of the area considered the majority of floods to be a function of the scale of the water management infrastructure and there was a keen awareness, which seems to have been based on past experience of flooding among affected communities, of the implications of upstream water storage and diversion schemes. One must bear in mind that residents also had an awareness of the way in which social power differentials influenced access to resources and vulnerability to floods. It is likely, therefore, that water users, be they vulnerable communities or individual hacendados were more likely to suggest social explanations for flooding (or water deprivation), especially where compensation for damages could be secured or where water rights and access agreements could be modified. Such trends have been recognized in investigations of contemporary flood-prone societies elsewhere.⁹⁴

Archival documentation indicates that the number of recorded floods in Guanajuato and the scale of damage caused by flooding escalated in the later colonial period. A cluster of highly destructive—and hence memorable and well-documented—floods was recorded in the second half of the eighteenth century. By this time, the level of water management, storage and diversion in the region had reached its zenith. It may be, therefore, that flood risk was exacerbated by the degree of water manipulation in the region and so had a predominantly human cause. To some extent this apparent increase in flood activity in the later colonial period reflects more general social and economic trends. Population increases and economic development in the seventeenth and eighteenth centuries meant a greater number of potentially vulnerable people and an increased risk associated with floods by this stage. The apparent increase in flooding also may reflect the expansion in mining and the cumulative effect of centuries of deforestation, both contributing to the erosion of sediment into the river valleys of the region. These anthropogenic causes of flooding certainly could explain the concern over sediment build up and the frequent references to the need to dredge and clear river channels at this time. One must also consider that the eighteenth century is better documented than earlier periods, and hence a record of floods from that period are more likely to appear in the archives, a factor that may well skew any trends we might elicit from the archival records.

Floods prompted tactical and strategic responses by individuals and communities and in some instances, structural responses led or financed by local governments. Although some documents indicate differences of opinion over the causes of flooding between different strata of society, many others suggest shared concerns over the effects of floods generally. There is some evidence of community participation in flood management and alleviation. The devastating events of the second half of the eighteenth century affected all sectors of society, but the archival documentation indicates that shared experiences and losses inspired a degree of collaboration and cooperation, not only in terms of recovery and response but also in the development and implementation of flood alleviation schemes. Examining the various projects proposed to control or mitigate flooding in Guanajuato provides insight into the degree interaction between different sectors of society in response to catastrophic events and highlights how societies were to some extent willing to tax themselves in terms of labor and money to avoid future flood losses. This kind of cooperation is particularly significant when set against the turbulent social and economic context of late-eighteenth-century Bajío in general. Though scholars have argued that eighteenth century interactions between indigenous and Hispanic groups in Guanajuato were characterized by conflict and dispute over land, labor, and water, the archives raise questions about shared environmental values and concerns between different social groups and how these contributed to cooperation and collaboration, transcendeding social and class divides.

Today, many people are interested in reducing vulnerabilities and damage associated with isolated extreme weather events such as storms and recurring droughts or floods.⁹⁵ While the use of archival sources for the reconstruction of climatic history is fraught with difficulties, historical documents nevertheless provide insight into how people were affected by, responded to, and conceptualized environmental risk and vulnerability. These sources speak to the level of environmental awareness and highlight how people understood and used environmental knowledge to address and respond to changes in water availability. The rich colonial archives represent but one source of invaluable historical information in this respect. More investigations of this type in locations with similarly rich archival legacies should now be seen as imperative.

Georgina Endfield is a senior lecturer in geography at the University of Nottingham, England. Her research interests include historical environmental change and human responses in Mexico and southern Africa and the history of extreme weather events and their effects. Isabel Fernández Tejedo is a researcher in history with interests in the pre- and post-Hispanic agricultural populations of Mexico and their interactions with the physical environment. Sarah O'Hara is a professor of geography at the University of Nottingham, England. Her research interests include recent and long-term environmental change in Mexico and human–environmental interactions in dryland environments, including Central Asia.

Notes

This paper represents research conducted as part of an Arts and Humanities Research Board (AHRB) funded project investigating "Agrarian responses to extreme climate events in colonial Mexico: 1521–1821," reference number B/RG/ AN6160/ APN 10797. The authors are very grateful to the AHRB for making this research possible. The authors would like to thank anonymous reviewers for their constructive comments on the initial manuscript.

^1. See, for example, Ted Steinberg, Acts of God: The Unnatural History of Natural Disaster in America (Oxford: Oxford University Press, 2000).

^2. See, for example, Piers Blaikie, Terry Canon, Ian Davis, and Ben Winser, At Risk: People's Vulnerability and Disasters (London: Routledge, 1994); Diana Liverman, "Drought Impacts in Mexico: Climate, Agriculture, Technology, and Land Tenure in Sonora and Puebla," Annals of the Association of American Geographers (1990): 49–72.

^3. Bajío literally means "lowlands." The area lies in the mesa central of the country and is a volcanic basin ringed by volcanic cones. The Bajío's environmental history is discussed in Karl W. Butzer and Elizabeth K. Butzer, "The Natural Vegetation of the Mexican Bajío: Archival Documentation of a Sixteenth Century Savannah Environment," Quaternary International (1997): 161–72.

^4. John Tutino, From Insurrection to Revolution in Mexico: Social Bases of Agrarian Violence, 1750–1820 (Princeton: Princeton University Press, 1988).

^5. Ibid.; Eric Van Young, The Other Rebellion : Popular Violence, Ideology and the Mexican Struggle for Independence, 1810–1821 (Stanford, Calif.: Stanford University Press, 2001).

^6. Enrique Florescano, Origen y desarollo de los problemas agrarios de Mexico (1500–1821) (Mexico: Ediciones Era, 1976); Enrique Florescano, "Una historia olvidada: la sequia en Mexico," Nexos (1980): 9–13; Diana Liverman, "Vulnerability to Drought in Mexico: The Cases of Sonora and Puebla," Annals of the Association of American Geographers (1990): 49–72; Diana Liverman, "Vulnerability and Adaptation to Drought in Mexico," Natural Resources Journal (1999): 99–115; Virginia G. Acosta, "Las Sequias Historicas de Mexico" La Red (1993): 2–18; Arij Ouweneel, Shadows over Anahuac: An Ecological Interpretation of Crisis and Development in Central Mexico, 1730–1800 (Albuquerque: University of New Mexico Press, 1996).

^7. James D. Riley, "Public Works and Local Elites: The Politics of Taxation in Tlaxcala, 1780–1810," The Americas (2002): 355–93.

^8. Helmut E. Landsberg, "Past Climates from Unexploited Written Sources," Journal of Interdisciplinary History (1980): 631–42; Emmanuel Le Roy Ladurie, Historie du Climat depuis l'an Mil (Paris: Flammarion, 1983); C. Ballard, "Drought and Economic Distress in South Africa in the 1800s," Journal of Interdisciplinary History (1986): 359–78; Sarah E. Metcalfe, "Historical Data and Climatic Change in Mexico—a Review," The Geographical Journal (1987): 211–22; Sarah L. O'Hara and Sarah E. Metcalfe, "Reconstructing the Climate of Mexico from Historical Records," The Holocene (1995): 485–90; Jean M. Grove, "Tax Records from West Norway as an Index of the Little Ice Age," Climatic Change (1983): 265–82; Jean M. Grove, The Little Ice Age (London: Methuen, 1988); Jean M. Grove, "The Initiation of the Little Ice Age in Regions Round the North Atlantic," Climatic Change (2001): 53–82; Jean M. Grove and A. Conterio, "The Climate of Crete in the Sixteenth and Seventeenth Centuries," Climatic Change 30 (1995): 223–47; David J. Nash and Georgina H. Endfield, "A Nineteenth Century Climate Chronology for the Kalahari Desert Derived from Missionary Correspondence," International Journal of Climatology (2002): 821–41; R. Grundmann and N. Stehr, "Social Science and the Absence of Nature: Uncertainty and the Reality of Extremes," Social Science Information (2000): 155–79; J. J. McCarthy, O. F. Canziani, N. A. Leary, D. J. Dokken, and S. Kasey Climatic Change 2001: Impacts, Adaptation, and Vulnerability (Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change, Intergovernmental Panel on Climate Change, Geneva, Switzerland, 2001).

^9. On demographic changes, see Sherburne Cook and Woodrow Borah, "The Indian Population of Central Mexico, 1531–1610," Iberoamericana (1960); Barbara Williams, "Tepetate in the Valley of Mexico," Annals of the Association of American Geographers (1972): 618–26.
On adjustments in land tenure, see Elinor M. Barrett, "Encomiendas, Mercedes, and Haciendas in the Tierra Caliente of Michoacán," Latinamerikas, (1973): 71–111; Hanns Prem, "Early Spanish Colonization and Indians in the Valley del Atlixo, Puebla," in Explorations in Ethnohistory: Indians in Central Mexico in the Sixteenth Century, ed. H. R. Harvey and Hanns J. Prem (Albuquerque: University of New Mexico Press, 1984), 205–28; Hanns J. Prem, "Spanish Colonisation and Indian Property in Central Mexico, 1521–1620," Annals of the Association of American Geographers (1992) 444–61; Jack A. Licate, Creation of a Mexican Landscape: Territorial Organization and Settlement in the Eastern Puebla Basin, 1520–1605 (Research paper number 201, Department of Geography, University of Chicago, 1981); Sergio Navarette Pellicer, "Las transformaciones de la económia indígena en Michoacán: siglo XVI," in Agricultura indigena pasado y presente, ed. Teresa Rojas-Rabiela (Mexico City: Centro de Investigaciones y Estudios Superiores en Antropología, 1994), 109–28.
On agriculture, see Lesley Bird Simpson, Exploitation of Land in Central Mexico in the Sixteenth Century (Berkeley: University of California Press, 1952); William B. Taylor, Landlord and Peasant in Colonial Oaxaca (Stanford, Calif.: Stanford University Press, 1972); William T. Sanders, "Ecology and Cultural Syncretism in Sixteenth Century," Mesoamerica Antiquity (1992): 172–90.

^10. Elinor G. K. Melville, "Environmental and Social Change in the Valle del Mezquital, Mexico, 1521–1600," Comparative Studies in Society and History (1990): 24–53; Elinor G. K. Melville, A Plague of Sheep: Environmental Consequences of the Conquest of Mexico (Cambridge: Cambridge University Press, 1994); Karl W. Butzer and Elizabeth K. Butzer, "Transfer of the Mediterranean Livestock Economy to New Spain: Adaptation and Ecological Consequences," in Global Land Use Change, ed. Billie Lee Turner, and Sal. A. Gomez (Mexico City: Consejo Superior de Investigaciones Cientificas, 1995), 151–93; Karl W. Butzer and Elizabeth K. Butzer, "The Sixteenth Century Environment of the Central Mexican Bajío: Archival Reconstruction from Colonial Land Grants and the Questions of Spanish Ecological Impact," in Culture, Form and Place: Essays in Cultural and Historical Geography, ed. Kent Matthewson (Baton Rouge: Louisiana State University Press, 1993): 89–124; Karl W. Butzer and Elizabeth K. Butzer, "The 'Natural' Vegetation of the Mexican Bajío: Archival Documentation of a Sixteenth Century Savannah Environment," Quaternary International (1997): 161–72; Andrew Sluyter, "Landscape Change and Livestock in Sixteenth-Century New Spain: The Archival Database," Yearbook, Conference of Latin Americanist Geographers (Austin: University of Texas Press, 1997), 27–39; Andrew Sluyter, "Colonialism and Landscape in the Americas: Material/Conceptual Transformations and Continuing Consequences," Annals of the Association of American Geographers (2001): 410–29; Andrew Sluyter, Colonialism and Landscape: Postcolonial Theory and Applications (New York: Rowman & Littlefield, 2002); Georgina H. Endfield and Sarah L. O'Hara, "Degradation, Drought and Dissent: An Environmental History of Colonial Michoacán, West Central Mexico," Annals of the Association of American Geographers (1999): 402–19.

^11. Susan C. Swan, "Mexico in the Little Ice-Age," Journal of Interdisciplinary History XIV (1981) 633–48; Enrique Florescano, Susan Swan, M. Menegus, and I. Galindo, Breve historia de la sequia en Mexico (Veracruz: Universidad Veracruzana, 1995); Sonya Lipsett-Rivera, "Puebla's Eighteenth Century Agrarian Decline: A New Perspective," Hispanic American Historical Review (1980): 463–81; Sonya Lipsett-Rivera, "Agua y supervivencia urbana en el medio rural poblano del siglo XVIII" in Estudios sobre y ambiente en América Latina, I. Argentina, Bolivia, México, Paraguay, ed. Bernardo García Martínez and Alba González Jácome (Mexico City: El Colegio de México/Instituto Panamericano de Geografía e Historia, 1999); Sonya Lipsett-Rivera, To Defend Our Water with the Blood of Our Veins: The Struggle for Resources in Colonial Puebla (Albuquerque: University of New Mexico Press, 1999); Sonya Lipsett-Rivera, "Indigenous Communities and Water Rights in Colonial Puebla: Patterns of Resistance," The Americas (1992): 463–83; Michael C. Meyer, El Agua en el suoest hispanico. Una historia social y legal 1550–1850, (Mexico City: Centro de Investigaciones y Estudios Superiores en antropologia Social, 1997); Georgina H. Endfield and Sarah L. O'Hara, "Conflicts over Water in the Little Drought Age in Central Mexico" Environment and History (1997): 255–72.

^12. Metcalfe, "Historical Data and Climatic Change in Mexico," 211–22; O'Hara and Metcalfe "Reconstructing the Climate of Mexico," 485–90; Sarah L. O'Hara, "Historical Evidence of Fluctuations in the Level of Lake Pátzcuaro, Michoacán, Mexico over the Last 600 Years," Geographical Journal (1993): 51–62; Ernesto Jauregui, "Climatic Changes in Mexico during the Historical and Instrumented Periods," Quaternary International (1997): 7–17; Butzer and Butzer, "The 'Natural' Vegetation of the Mexican Bajío," 161–72; Georgina H. Endfield, Isabel Fernández Tejedo, and Sarah L. O'Hara, "Drought and Disputes, Deluge and Dearth," Journal of Historical Geography (2004), in press; Riley "Public Works and Local Elites," 355–93.

^13. References to archival sources are cited as follows: Archives consulted in the Archivo General de la Nación, Mexico City, (AGN):

AGN followed by ramo:
AGN Mercedes (land grant documents)
AGN Tierras (litigation records)
AGN Indios (indigenous affairs)
AGN Civil (civil registers)
AGN General de Parte (administration records)
AGN Alhóndigas (crop records)
AGN Historia (documents dealing with local historical information)
AGN Tributos (tribute listings)
AGN Hospital de Jesus (Jesuit records)
AGN Salinas (salt records)
AGN Rios y Acequias (river and dam records).

Archives consulted in the Archivo Historico Municipal de Leon: AHML followed by name of ramo; Archives consulted Archivo Casa de Morelos, Morelia: ACM followed by expediente and page number. Archivo Historico del Estado de Guanajuato: AHEG; Archives consulted in the Museo Nacional de Antropologia, Archivo Historico: MNA. AH.
In all cases, archives will be referenced in the following manner: the Ramo, the volume number, the expediente (if applicable), and/or the page (foja) number: e.g AGN Tierras vol. 2345, exp. 1, fa. 23; AGN Indios, vol. 15, exp. 2, fs. 33–35.

^14. See for example, Ciudad Real, "Descripcion de la Ciudad y Real de Minas de Guanajuato por José Hernandez Chico, 1788," Archivo de la Marina, Museo Naval de Madrid, Ms 563; Enrique Florescano and Isabel Gil, eds., Descripciones económicas regionales de la Nueva España 1766–1827 (Mexico City: SE-INAH, 1976); Alejandro Humboldt, Ensayo politico sobre el reino de la Nueva Espana (Mexico City: Editorial Porrua S.A., 1973); Lucio Marmolejo, Efemérides Guanajuatenses o datos para formar la historia de la ciudad de Guanajuato, vol. 1 (Guanajuato: Universidad de Guanajuato, 1967).

^15. Fekri Hassan, "Environmental Perception and Human Responses in History and Prehistory," in The Way the Wind Blows: Climate, History and Human Action, ed. Roderick J. McIntosh, Joseph A. Tainter and Susan K. McIntosh (New York: Columbia University Press, 2000), 121–40.

^16. Zbigniew W. Kundzewicz and Zdzislaw Kaczmarek, "Coping with Hydrological Extremes," Water International (2000): 66–75.

^17. Landsberg, "Past Climates from Unexploited Written Sources," 631–42.

^18. David Brading, Haciendas and Ranches in the Mexican Bajío, Leon, 1700–1860 (Cambridge: Cambridge University Press, 1978), 14.

^19. Michael E. Murphy, Irrigation in the Bajío Region of Colonial Mexico (Boulder, Colo., and London: Westview Press, 1986): 7–8.

^20. Archaeological evidence of pre-Classic settlement in the region includes Chupicuaro, the burial ground of a village which lay above the Lerma River and which gave its name to a complex that was relatively widespread in the region. See Michael D. Coe, Mexico, from the Olmecs to the Aztecs (London: Thames and Hudson, 1994). For more detailed considerations of pre-Hispanic groups in the Bajío, see Wilberto Jimenéz Moreno, "La colonización y evangelización de Guanajuato en el siglo XVI," in Estudios de Historia Colonial (México City: INAH, 1958), 63–94; and David Wright Carr, La conquista del bajío y los orígenes de San Miguel de Allende, (Mexico City: FCE y UVM, 1998): 21–22. The "Chichimecas" or "dog Indians" frequently attacked early settlements and presented one of the main obstacles to Spanish colonization of the area.

^21. Brading, Haciendas and Ranches, 16.

^22. AGN General de Parte vol. 1, exp. 1304.

^23. AGN General de Parte vol. 2, exp. 60; vol. 4; exp. 266; vol. 6, exp. 794; AGN General de Parte vol. 5, exp. 226.

^24. AGN Mercedes vol. 5, 120v; AGNT vol. 675, exp. 1, fa. 75; AGNT vol. 136, parte 1a. See also, P. Martinez de la Rosa, Apunte para la Historia de Irapuato (México City: Biblioteca de Historia Mexicana, Castalia 1965).

^25. ANG Tierras vol. 741, exp. 1; fa. 55.

^26. Butzer and Butzer, "The Sixteenth Century Environment of the Central Mexican Bajío," 89–124.

^27. Butzer and Butzer, "The 'Natural' Vegetation of the Mexican Bajío," 170.

^28. Brading, Haciendas and Ranches, 17.

^29. ANG Tierras vol. 988, exp. 2, fa. 92.

^30. François Chevalier, La formación des grandes domaines au Mexique: terre et societé aux XVI–XVII siécles (Paris: Institut d'Ethnologie, 1952).

^31. Humboldt, Ensayo politico, 258.

^32. AGN Mercedes 8, fs. 2, 29, 40, 43, 55, 87, 100, 111, 113, 118, 190.

^33. See, for example, numerous references to "waterlifts" ornorias in AGN Historia 72, exp. 9; AGN Civil, vol. 73, exp. 3; AGN Tierras vol. 514, exp. 1, cuad. 2, fa. 47; AGN Tierras, vol. 618, exp. 1, cuad. 3, fa. 61; AGN Tierras vol. 1353, exp. 1, fa. 69.

^34. Murphy, Irrigation in the Bajío, 24.

^35. ANG Tierras 2705, exp. 3, fa. 1; AGN Mercedes, vol. 10, fa. 3.

^36. Murphy, Irrigation in the Bajío, 33.

^37. Humboldt, Ensayo politico.

^38. Rabel Romero, C. E., San Luis de la Paz, estudio de economica y demografia historicas, 1645–1810. (Ph. D. diss., Instituto Nacional de Antropología y Historia, Mexico, 1975), cited in Brading, Haciendas and Ranches, 21.

^39. Brading, Haciendas and Ranches, 18.

^40. Endfield and O'Hara, "Conflicts over Water," 255–72.

^41. Secretaria recursos hidraulicos, (Mexico City, 1980): Appendix 3; Humboldt, Ensayo politico, 255.

^42. Alvarado Gómez and Antonio Armando, El comercio interno de la Nueva España, el basto de la ciudad de Guanajuato, 1777–1810 (México City: INAH, 1995); Tutino, From Insurrection to Revolution in Mexico, 1988.

^43. AGN A, vol. 108, exp. 2, 6; AGN Tierras vol. 1362, cuad 12 fa. 38; vol. 1390, exp. 3, fa. 34.

^44. Ouweneel, Shadows over Anáhuac, 92; Endfield and O'Hara, "Conflicts over Water." 255–72.

^45. See, for example, AGN Tierras, vol. 674, exp 1, 30. Follow the dispute in vol. 675, exp 1; AGN Tierras vol. 192, exp. 1; AGN Tierras, vol. 586, exp 8; AGN Tierras, vol. 1872, exp. 15 10; AGN Tierras, vol. 671, exp. 3, 18; AGN Tierras, vol. 2901, exp. 36; AGN Tierras, vol. 2959, exp 141; AGN Tierras, vol. 988, exp. 1–3 , 516; AGN Tierras, vol. 1110, exp. 18; AGN Tierras, vol. 1166, exp. 1, fs. 450; AGN Tierras, vol. 2963, exp. 116, fs. 246–308; AGN Tierras, vol. 1352, exp 1; AGN Tierras, vol. 1368.

^46. AGN Tierras, vol. 674, cuad 1, fs. 100–106.

^47. AGN Tierras, vol. 187, exp. 2, fs 94–108.

^48. AGN Tierras, vol. 671, exp. 3, fa. 18.

^49. Murphy, Irrigation in the Bajío, 81–86.

^50. AGN Tierras vol. 2680, exp. 29.

^51. AGN Indios, vol. 5, exp. 154; AGN Indios, vol. 5, exp. 598.

^52. AGN Tierras, vol. 187, exp. 2, 327.

^53. AGN Tierras, vol. 1110, exp. 18.

^54. Lipsett-Rivera, "Puebla's Eighteenth Century Agrarian Decline," 463–81.

^55. Acosta Las Sequias Historicas de Mexico, 1993.

^56. AGN Obras Publicás 17, exp. 10, fa. 43.

^57. Ciudad Real, "Descripcion," 30.

^58. Ibid.

^59. AHML Inundaciones exp. 3.

^60. Marmolejo, Efemérides Guanajuatenses, 181.

^61. R. Douglas Cope, The Limits of Racial Domination: Plebeian Society in Colonial Mexico City, 1660–1720 (Madison: University of Wisconsin Press, 1995).

^62. Jean Pierre, "La peste de 1643 en Michoacán," in Historia y Sociedad en el Nuevo Mundo de habla española ed. José Miranda, (México City: El Colegio de México, 1970), 247–61; Manuel Orozco y Berra, Historia de la dominación española en México, con una advertencia de Genaro estrada (Mexico City: Biblioteca Historica Mexicana de obras ineditas Núm 10, 1938) 242–48.

^63. Marmolejo, Efemérides Guanajuatenses.

^64. AGN Alcade Mayores, vol. 1, exp. 309, fs. 439–41.

^65. AGN Tierras, vol. 2071, exp. 1, fs. 1–110.

^66. AGN Tierras, vol. 1390, exp. 3, fs. 34, 1790.

^67. AGN Tierras, vol. 2072, exp 1.

^68. Cited in Heriberto Moreno, Francisco de Ajofrín, Diario del Viaje a la Nueva España (Mexico: Secretaria de Educación Publica, 1986).

^69. AGN Rios y Acequias, vol. 1: exp. 9, 214.

^70. Endfield and O'Hara, "Degradation, Drought and Dissent," 402–19; Ouweneel, Shadows over Anáhuac, 38.

^71. Sarah E. Metcalfe, Elaine A. Street-Perrott, R. B. Brown, P. E. Hales, R. A. Perrott, and F. M. Steininger, "Late Holocene Human Impact on Lake-basins in Central Mexico," Geoarchaeology 4 (1989): 119–41.

^72. Butzer and Butzer, "The Natural Vegetation of the Mexican Bajío," 170.

^73. AGN Caminos y Calzadas, vol. 2, exp. 8, fs. 121–24.

^74. AGN Bienes de Comunidad, vol. 2, exp. 295, fs. 369.

^75. AGN Rios y Acequias, vol. 4, exp. 2.

^76. AGN Obras Públicas, 17, exp. 10, fs. 43.

^77. AGN Obras Públicas, vol. 5, exp. 5, fs. 249–68.

^78. AGN Tierras , vol. 1362, exp. 1.

^79. AGN Tierras 1197, exp 2.

^80. Rafael Zamarroni Arroyo, Naraciones y Leyendas de Celaya y del Bajío vol. 1 (Mexico City: Editorial Periodistica e Impresora de Mexico, 1960).

^81. Murphy, Irrigation in the Bajío, 36.

^82. AGN Rios y Acequias, vol. 1, exp. 9, 214.

^83. AGN Bienes de Communidad, vol. 2, exp. 153.

^84. AGN Intendencias, vol. 81, exp. 1.

^85. AGN Bienes de Comunidad, vol. 2, exp. 237, fa. 310.