Summary based on a study by Donald A. Wilhite, Center for Agricultural Meteorology and Climatology, University of Nebraska, Lincoln, NE.
The Ogallala Aquifer underlies approximately 225,000 square miles in the Great Plains region, particularly in the High Plains of Texas, New Mexico, Oklahoma, Kansas, Colorado, and Nebraska. The depth of the aquifer from the surface of the land, its reate of natural thickness, vary from region to region. The aquifer has long been a major source of water for agricultural, municipal, and industrial development.
Use of the aquifer began at the turn of the century, and since World War II reliance on it has steadily increased. The withdrawal of this groundwater has now greatly surpassed the aquifer's rate of natural recharge. Some places overlying the aquifer have already exhausted their underground supply as a source of irrigation. Other parts have more favorable saturated thicknesses and recharge rates, and so are less vulnerable.
There have been several major studies of the Great Plains in the past fifty years; the Great Plains Report (1936), the Travelers Insurance studies of the Great Plains (1958-59) and the most recent Six-State High Plains Study (1982). An assessment of these studies and their findings could provide insight into how climate considerations have been used by the studies' authors.
The first study (the Great Plains Report) was sparked by the prolonged and devastating droughts of the 1930s in the Great Plains, a region subject to recurring drought episodes. In an attempt to identify why the impacts of those droughts were so bad, attention focused on regional land use practices. To prevent dust storms, soil erosion, and what today would be referred to as desertification processes in general, it was recommended that better land use practices be pursued and that some of the most vulnerable areas should be taken out of cultivation and put into rangeland use for livestock. Surprisingly, little mention was made about the climate of the region, aside from climate as a boundary constraint.
The 1958-59 Travelers Insurance study looked at the prospects for the future of irrigation development in the Great Plains in the following decades. The study disclosed that while the future was bright for irrigators in the northern High Plains area, it was relatively less favorable for the southern High Plains. Climate was also not considered in this study, except as a boundary condition. More specifically, climate variability and change were not taken into consideration.
The most recent High Planes-Ogallala Aquifer Regional Resources study was sponsored by the US Department of Commerce (DOC) and was released in mid-1982. It treated climate as a given, and a favorable given at that. Nowhere in the study is climate variability or climate change mentioned. The DOC assessment was completed at a time when there was considerable discussion about the prospects for a global climate change and a possible increase in climate variability. It is interesting that considerations of either climate variability or climate change were absent from the multimillion-dollar report as well as from most reviews of it. The study focused on water balance in the region and on the economics associated with dwindling groundwater supplies. Asided from other problems with the study the lack of consideration of climate (other that that it would continue to be benign) makes its projections regarding possible future scenarios about, for example, agricultural production costs, less than useful.
Societal responses to relatively short-term climatic extremes often spark a search for new technological changes on which societies then become increasingly dependent. A good example of this would be the recurrent droughts in the Great Plains which ultimately led to a regional dependence on the use of groundwater for agriculture. The dependence on groundwater introduces an element of control by society over water resources and their use.
Policies developed in response to depletion of the aquifer that may be technically and economically feasible must also be politically and socially acceptable. For example, the suggested large-scale interbasin water transfers to this region from the Great Lakes or some other river basin may be sound technical projects but they face considerable social and political opposition.
The rates of drawdown and recharge of the aquifer vary from one locale to another. As a result, not all counties within a state or all states within a state or all states within the Ogallala region are confronted by the same degree of crisis. This difference translates into varying degrees of concern about the depletion of the Ogallala Aquifer with, for example, Texas being more concerned than Nebraska (which happens to have the most favorable recharge rate of all areas throughout the region that overlays the aquifer). As a result, in time we may see a Texas strategy or a southern High Plains strategy emerge as opposed to a six-state High Plains strategy being developed and pursued.
Is the drawdown a national problem? How concerned should national leaders be about the depletion of this aquifer? This question raises a dilemma for some of those immediately affected. While on the one hand there is interest within the states in generating national concern about the "problem," on the other hand, there is a strong desire to keep control of the aquifer and its management at the local and state levels. Because of the local variations in aquifer thickness, people in the region prefer local responses to local changes in the aquifer. In fact, a pecking order of preferences emerges from inhabitants of the region: state involvement is preferred over federal, and conservation measures are preferred over reverting to dryland farming practices.
The drawdown of the aquifer raises an important issue that permeates discussions about the social and political responses to a global warming: discounting the future. Here is a good example of a choice that society must make - consume the groundwater resource today or conserve it for future generations when climate in the region might not be as favorable to agricultural production as it is today. At which time would the groundwater resource be of most value? And to whom? Today, other factors have slowed down the rate of drawdown, such as relatively higher energy prices, low crop prices, large stockpiles of rain and so forth. Nevertheless, the issues of intergenerational equity should be addressed now when there is less pressure to decide one way or another.
Are the policy measures implemented in response to the Ogallala Aquifer depletion applicable to changes in regional water supplies that may result because of projected changes in climate due to increasing CO2? The depletion of the aquifer represents a change in the water balance of the Great Plains region, as would the suggested impacts of global warming. (Water balance refers to all sources of moisture in the region; atmospheric, surface, and groundwater.) With a warming, soil moisture in the region would be reduced, as would rainfall. By using the Ogallala Aquifer depletion as an analogue, scientists and policy makers can learn much about the process of evaluating and selecting socially acceptable policy responses to large-scale environmental issues. However, regional changes in climate of the magnitude suggested by GCM output may impose a new set of rules on society for choosing appropriate policy responses to climate related environmental change.
Summary of Chapter 15, The Ogallala Aquifer and Carbon Dioxide: Are Policy Responses Applicable?
by Donald Wilhite
Societal Responses to Regional Climate Change: Forecasting by Analogy, Michael H. Glantz, editor, Westview Press, Boulder, Co, 428 pp.