Water security and social-ecological-hydrological systems.
In the conservation classic, A Sand County Almanac, Aldo Leopold described his visit in 1922 to the Colorado River delta, noting abundant “green lagoons … walls of mesquite and willow … fleets of cormorants” and a “wealth of fish and fowl,” and many sightings of bobcats, racoons, coyotes, deer, and other wildlife. Prior to the time of Leopold’s visit, the Colorado River, which drains parts of seven states in the western United States, flowed almost freely some 1,500 miles southward from the Rocky Mountains to its delta on the Gulf of California in Mexico.
However, during the twentieth century, the U.S. government backed or built a series of large dams, canals, and irrigation projects which – under the terms of a 1944 binational treaty allotting the river’s flow among the basin states and Mexico – eventually diverted or impounded almost all water from the river. Over the years, that water has supplied the growing needs of agriculture, municipalities, and industries across the basin states, and to a lesser extent in northwest Mexico. With all water in the river “spoken for,” flows to the delta essentially had ceased. By 2005, only about 10% of the delta’s original wetlands and riparian (riverside) habitat remained. The lush and life-filled area described by Leopold had become a vast, barren land covered by salty and dried mudflats. The plentiful fisheries and wildlife populations all but disappeared. And the lifeblood for people and communities located in the delta region withered.
But the delta’s story has continued. To begin with, some decades ago, a small wetland – the Cienega de Santa Clara – re-emerged “by accident” when, in the late 1970s, water from an agricultural drainage area in southwestern Arizona was allowed to flow into the Gulf of California (because the water did not meet the quality standards obligated to Mexico by the treaty). Yet, even with a small amount of (unintentional) water flow – and subsequently with occasional unplanned flows that passed through the delta due to upstream floods in the 1980s and 1990s – small sections of the delta, such as the cienega, responded and slowly came back to life. The areas again became home to many species of fish and other wildlife, a stopover for North American migratory birds, and a source of livelihood for the people inhabiting the area. This recovery process demonstrates the delta’s ecological and social resilience.
Resilience and water security
Resilience is defined as “the capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedback.” For example, while the “restored” areas in the delta are not the same as they were prior to the decades of water loss, they do exhibit similar characteristics and functions as they once did. Associated with resilience, in this case, is the concept of water security, which can be described as “the sustainable availability of adequate quantities and qualities of water for resilient societies and ecosystems in the face of uncertain global change.” Water security means that though physical or social conditions might change in an area, the people and ecosystems in that area will continue to have water of good quality and sufficient quantity. In the case of the Colorado River delta, the reliable presence of water is necessary not only to restore the wetland’s habitats and wildlife, but also to maintain those resources and the human livelihoods that depend on them.
The standard approach to water security has been through the human-centered use of technology – such as building dams, irrigation systems, treatment plants, and similar infrastructure. To a great extent this approach was successful in providing water of good quality to support large populations of humans around the globe. But in doing so, it turns out that this approach – large-scale control over natural systems – had many unintended, mostly negative, consequences. For example, while the widespread use of pivot-irrigation across the U.S. Great Plains increased agricultural yields by bringing arid and semi-arid lands into production, it also created increased reliance on (and depletion of) non-renewable water supplies, such as groundwater. While high dams, such as those on the Colorado River, have produced hydroelectricity and allowed water to be stored for use in times of need, the large reservoirs behind the dams have inundated many valuable ecosystems, geological features, cultural sites, and riverside communities. In the Colorado River delta, as the river’s water no longer reached the sea, local communities in Mexico whose livelihoods depended on the once rich delta ecosystem were left in a precarious situation. Thus, the byproducts of well-intended engineering solutions, while providing water security for some populations and areas, can at the same time adversely and inequitably threaten the security of others.
In recent decades, scientists have come to appreciate the complex, often uncertain, interactions of social, ecological, and hydrological systems, or s-e-h systems (Figure 1). An alternative approach to water security – compared to the technology-focused approach – is one that considers at the outset the potential outcomes of the integrated and dynamic s-e-h systems. The alternative approach assumes that altering any one system – as a means to provide water security – has the potential to change, through a rippling effect, the other systems as well, sometimes leading to the negative, unanticipated outcomes mentioned above.
Research has shown that the s-e-h systems are subject to many stresses. For example, the social system is characterized by rapidly growing populations and increased water demand. Societies also face the challenges to manage and allocate water equitably. The growing demand of water for humans affects the ecological system, such as by diminishing supplies to support wetland and riparian ecosystems. The degradation of the ecological system reduces ecosystem services – the services provided by nature for free, such as providing food and materials, cleaning the air and water, as well as aesthetic and cultural values. The reduction of ecosystem services, in turn, can affect the livelihoods of people. For example, as less water flows in a river and fisheries die, people who depended on fishing to survive would need to find other ways to make a living.
Additional stresses to the hydrological system can compound the pressures on the other systems. For example, under drought conditions, human consumption of water in arid lands might deplete available surface water supplies. In response, and to continue to provide water security, this might lead to the pumping of water from aquifers – as an alternative source of water supply – which in turn might also become depleted if the drought situation persists.
Under certain circumstances, changes in one system can push the other systems past certain limits, or thresholds, such that recovery from a disturbance or shock may not be feasible. Or, recovery might move in another direction rather than toward the pre-existing state (condition). For example, the effects of decades of water loss for the Colorado River Delta, if compounded by a prolonged and severe regional drought, could push the delta’s wetland ecosystem beyond its ability to recover, even if water supplies were restored.
The bottom line is that this alternative approach to water security assumes that because the s-e-h systems are interconnected, altering any one system as a means to serve a particular water security need, at the same time, as if through a rippling effect, could threaten the water security for humans and ecosystems at some point for some other place. Therefore, actions taken to support resilience and to provide water security for one area need to anticipate as best as possible, through the perspective of integrated s-e-h systems, the reactions, or side effects, that might result elsewhere.
In the case of the Colorado River delta, manipulation of the hydrological system (i.e., the diversion of water flows) is the key factor that triggered a change of state in both the ecological and social systems. The lack of water flow caused the area to become a derelict and dry place, and the local people suffered from this. The return of water to this area, though unintended, triggered an alternative change of state, restoring the ecosystem functions and bringing life back for both ecological and social systems that were resilient enough to endure decades of water loss and to respond to a small amount of water.
This response also offered a “proof of concept,” of sorts, which supported an unprecedented binational agreement signed in 2012. The agreement, which amended the terms of the 1944 U.S.-Mexico water treaty, allocated a portion of the Colorado River, through a one-time pulse flow, to supply water exclusively to the ecosystem of delta. Today, scientists, nongovernmental organizations, government agencies, and other stakeholders work together to understand the processes and systems of the delta, and to provide the basis and means to ensure for the delta a sufficient and secure water supply.
In Part 2 of this series (coming soon) we will discuss further the concepts of resilience and water security and how adaptive management and science-policy dialogues can serve to promote them.
 Aldo Leopold. 1949. A Sand County Almanac, Oxford University Press (Ballentine Books, 1971), 150-51.
 Walker, B., C. S. Holling, S. R. Carpenter, and A. Kinzig. 2004. Resilience, adaptability and transformability in social–ecological systems. Ecology and Society 9(2): 5. [online] URL: http://www.ecologyandsociety.org/vol9/iss2/art5.
 Scott, C.A.; Meza, F.J.; Varady, R.G.; Tiessen, H.; McEvoy J.; Garfin, G.M.; Wilder, M.; Farfan, L.M. Pineda Pablos, N. & Montaña, E. 2013. Water Security and Adaptive Management in the Arid Americas. Annals of the Association of American Geographers, 103(2), 280-289.
 The International Boundary and Water Commission (IBWC) (or CILA in Spanish) signed Minute 319 on November 20, 2012. In this agreement, for the first time in history, water was allocated for the restoration of the Colorado Delta ecosystem, for an interim five year period (2012-2017).
 Flessa, K.W., et al. 2013. Flooding the Colorado River delta: A landscape-scale experiment. EOS 94(50): 485-86.