Sustainable Management of Groundwater in Mexico: Proceedings of a Workshop (2007)

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Where do Decision-Makers Get Advice? Sustainability and Groundwater Management Decisions Stephen E. Ragone, National Groundwater Association A major issue facing global societies is water sustainability—having enough good- quality, reasonably priced water to meet all future needs, region by region. In seeking the goal of a sustainable future the decision maker must justify the cost to achieve this goal against expenditures to resolve more immediate and pressing societal problems. To do this, the decision maker must seek advice not only about the “controlling factors”—the climatic variability and the complexity of the groundwater system that affect the quantity, quality and distribution of water resources but also the “constraining forces”—the prevailing socio-economic conditions that affect decision-making. The decision maker must also seek advice about emerging technologies that may serve to conserve or augment natural water resources. So, the short answer to the question, “Where do decision makers get scientific advice?” is, “It depends”—on the mix of controlling factors and constraining forces that affect water resources at the place of interest. The Complexity and Interconnectedness of Groundwater Systems A groundwater system (Figure 1) consists of a sequence of continuous and discontinuous aquifers (saturated, permeable consolidated or unconsolidated geologic units that can transmit “usable” quantities of water) and confining beds (geologic units that restrict the movement of water into and out of adjacent aquifers). The water table defines the boundary between the uppermost aquifer—the unconfined aquifer—with the overlying unsaturated geologic unit (the unsaturated zone or vadose zone, not defined on Figure 1. The lateral boundaries and vertical extent of a groundwater system can vary widely as determined by the conditions under which the geologic units were formed. Heath (1984) provides an excellent summary of the physical, chemical, and hydraulic characteristics that delineate different types of regional groundwater systems. It is these characteristics that determine, among other things, the volume of water in a groundwater system and time of travel of water through the system—which can range from days to millennia. Current distributions of water in regional groundwater systems generally developed since the end of the last ice age some twenty thousand years ago. During this period glaciers retreated and left behind reconfigured surface-water and shallow groundwater systems in many parts of the world. A dynamic equilibrium was established among: the water recharging the groundwater system, that which was held in storage and that which discharged from the system (see “A” in Figure 2.) There was little exchange of water between shallow groundwater and that in the deeper, confined parts of regional groundwater systems prior to development. In humid areas the regional systems were, “brim full; that is, most of the potential recharge was rejected….” (Johnson, 1999). Likewise, in drier regions, “recharge to and flow through most regional aquifers were small before development.” (Johnson, 1999) Thus, under pre-development conditions, most of the annual recharge of water to regional systems entered and moved through the 44 

unconfined aquifers en route to surface water bodies. It is this part of the groundwater system that is often used to estimate the part of global water resources that is available for human use—the “mean annual river runoff and annually renewable groundwater resources….” (Shiklomanov, 1993) The reality, however, is that pumpage from deeper confined parts of groundwater systems is now routinely used to supply water in many places throughout the world—but not without effect. Pumpage from confined regional aquifers alters the dynamic equilibrium (see “B” in Figure 2) and, thus, the volumes of water being recharged, held in storage or being discharged. The characteristics of the system determine the specific response to pumpage. The Southern High Plains aquifer (Figure 3), for instance, responded to pumpage predominantly with a decrease in storage, and an increase in induced recharge and the infiltration of irrigation water. The Edwards aquifer, on the other hand, responded to pumpage predominantly with a decrease in discharge to streams and an increase in induced recharge. The other regional aquifers included in Figure 3 show other combinations of responses to pumpage. Figure 1 Simplified Groundwater system. Response time to pumpage can vary widely as well. Alley and others (2002) demonstrate that an aquifer’s response to some hydraulic perturbation can vary from hundreds of minutes (for horizontal flow in a confined stream-aquifer system) to thousands of years (for vertical flow in a thick regional low-permeability unit.) Water-quality changes can take even longer as such changes depend on the physical movement of water. It would take 82 years for water to move under natural conditions through the entire width of the confined stream-aquifer system described above, for instance (Alley and others 2002.) 45 

However, water-quality change in fractured rock systems or in groundwater systems that are being intensively pumped can be relatively rapid. The interconnection between groundwater and surface waters can be significant. Winter and others (1998) found, for instance, that groundwater contributes from 14 to 90 percent (median of 55 percent) of the streamflow of 54 streams throughout the United States. The interconnection between groundwater and surface water reinforces the “common- good” valuation of groundwater (as compared with its value as a commodity) and that-- “many uses and environmental values depend on the depth to water—not the volumetric amount of (groundwater) that is theoretically available.” (Sophocleous, 2003) Figure 2 Groundwater balance before (A) and after (B) development. 46 

Figure 3 Hydrologic responses to pumpage of major aquifer systems in the United States (from Alley and others, 2002). Thus, when seeking scientific advice the decision maker must be aware of the complex nature of groundwater systems and that their response to pumpage can vary in both space and time. As most water-management actions take place at the local and regional scales, the decision maker must also be aware of the different water supply and waste disposal requirements of urban, rural and agricultural areas in his/her region, as well as the role of planned and inadvertent point and nonpoint pollution in either diminishing the availability of usable water reserves or increasing water-development costs. Finally, the decision maker must recognize the role groundwater plays as part of the broader ecological system, “the running streams, wetlands, and all the plants and animals that depend on it,” (Sophocleous, 1997). 47 

Weighing the Tradeoffs The recent droughts in the United States caused significant decreases in surface water reserves and water table elevations thus reinforcing a growing concern that demand for water is outstripping supply, and causing state agencies and water managers to take unprecedented actions to prioritize and regulate water use even in parts of the country that were once considered to be “water rich.” “The United States has had (many) droughts since the 1930s (the time of the “Dust Bowl” that added to the economic travails of the Depression years and undermined social structures.) With each drought the concern was raised that water supplies were no longer adequate to meet demands. However, the improved water-supply infrastructure (particularly the advent of large, high-volume pumps used to tap into deep, confined aquifers) and federal support programs made such concerns short-lived. So, what is it about the recent drought that seems more foreboding? One reason is the large increase in population--from about 50 million people to more than 250 million--that occurred in the United States during the last century and the consequent increase in water withdrawals (National Research Council, 2002). A disproportionately large part of the increase occurred in arid and semi-arid regions, and urban centers, thus effectively increasing the net imbalance between local supply and demand. Also, the pervasive nature of the drought--affecting water-rich and arid regions, and people in agricultural, rural, and urban areas—and concerns about global climate change--reinforced perceptions that more severe droughts would happen more often and in more places....”(Ragone and Sophocleous, 2004). In the United States the public’s growing disaffection with dams—a social phenomenon arising out of ecological concerns--and the fact that virtually all surface waters are fully allocated strongly suggests that groundwater will become a more important component of water supplies in the future. However, two factors work against its efficient and, maybe, appropriate development. The first is the bureaucratic/regulatory water resources management framework that developed over time—one that separates the regulation and management of surface waters and groundwaters--and the state regulations and interstate compacts that often “lock in” inefficient land-use and water-use practices (see Maguire this volume). The second factor is that the increasing value of groundwater as a commodity (as opposed to water’s value as a common good as described above) can lead to its exploitation. “Over the years the intense use of groundwater for irrigation in the High Plains has caused major water-level declines and decreased the saturated thickness of the aquifer significantly in some areas....”(Taylor and Alley, 2001). Intensive pumpage of groundwater has resulted in instances of land subsidence and groundwater contamination in the High Plains aquifer and in other groundwater systems. In the face of such “negative outcomes” water purveyors often opt to tap into still pristine parts— deeper, confined parts--of groundwater systems rather than paying the high costs to renovate contaminated water and aquifers. As mentioned in the previous section such extractions from confined systems can significantly alter regional groundwater flow patterns. It can also accelerate groundwater contamination, thus further exacerbating current water shortages and potentially worsening future shortages. 48 

But, do the benefits derived from “exploitive” pumpage—improved agriculture or industrial productivity or domestic supplies--outweigh the negative effects? Freeze and Cherry (1978) recognize, that “from the optimization viewpoint, groundwater has value only by virtue of its use...that best meets a set of economic and/or social objectives....” Abderrahman (2003) reports that Saudi Arabia chose to use about 19% of its non- renewable groundwater resources between 1975 and 2000 to support socioeconomic development in rural areas—to help rural populations and nomads “to be converted into skilled agricultural communities...with effective public services (and to support) the security of the country....” Likewise, it could be argued that the “exploitation” of groundwater in parts of the High Plains aquifer to stabilize agricultural production and community structure following the droughts of the 1930s also served the United States well. Thus, although the consequences of the “exploitation” of water resources to meet immediate socio-economic needs may be viewed as undermining the long-term goal of sustainable water resources the decision about the “best” use of groundwater reserves will ultimately be decided by society as it ponders more pragmatic, present-day concerns. In response the decision maker will be required to choose a pathway to a sustainable future from the continuum of options that lie between “weak” and “strong” sustainability. “Weak Sustainability requires one generation to hand over to the next a nondeclining total capital stock (of water), which assumes that perfect substitution exists between different types of capital, e.g. new technologies for water treatment or improved water use efficiencies might be developed that somehow substitutes for the reduced capital stock of aquifer water. Strong sustainability, on the other hand, assumes that some kinds of natural capital have no substitutes.” (Alley and Leake, 2004) William Mills speaks to the issue of weak sustainability in his talk (this volume) about the efforts of the Orange County Water District to provide the technologies needed to ensure an adequate supply of water for its citizens. Gonzalo Merediz Alonso speaks (this volume) to the desire for strong sustainability in the Yucatan. A danger is that society will make such decisions only in response to immediate concerns and without necessary information about the longer-term outcomes of their decisions. Thus, it is essential that those giving scientific advice act in good faith and with objectively, and that the decision makers ask the right questions to ensure that this is so. 49 

References Abderrahman, W.A. 2003. Should intensive use of non-renewable groundwater resources always be rejected? in: Intensive Groundwater Use-Challenges and Opportunities, E. Custodio and R. Llamas (eds.) A.A. Balkema Publishers, Lisse, The Netherlands, 191-206. Alley, William M., Richard W. Healy, James W. LaBaugh and Thomas E. Reilly. 2002. Flow and Storage in Groundwater Systems, Science, volume 296. Alley, William M., and Leake, Stanley A. 2004. The Journey from Safe Yield to Sustainability; Groundwater, volume 42, number 1. Freeze, R. Allen and Cherry, John A. 1978. Groundwater; Prentice-Hall International, Inc. London. Johnson, Richard H. revised 1999. Hydrologic Budgets of Regional Aquifer Systems of the United States for Predevelopment and Development Conditions; U.S. Professional Paper 1425. Heath, Ralph C., 1984. Groundwater Regions of the United States; U.S. Geological Survey Water-Supply Paper 2242. National Research Council. 2002. Estimating Water Use in the United States: A New Paradigm for the National Water-Use Information Program; National Academy Press, Washington, D.C. Ragone, Stephen E. and Sophocleous, M.A. (2004). Perceptions and Realities about Groundwater and Future Water Availability; in New World Water (in press). Shiklomanov, Igor A., 1993. World fresh water resources, in Water in Crisis: A Guide to the World’s Fresh Water Resources, Peter H. Gleick editor; Oxford University Press, Oxford, England. Sophocleous, M.A., 1997. Managing water resources systems: Why safe yield is not sustainable; Groundwater volume 35, number 4. Sophocleous, M.A., 2003. Environmental implications of intensive groundwater use with special regard to streams and wetlands, in: Intensive Groundwater Use-Challenges and Opportunities, E. Custodio and R. Llamas (eds.) A.A. Balkema Publishers, Lisse, The Netherlands, pp.93-112. Taylor, C.J. and Alley, W.T. 2001. Groundwater-Level Monitoring and the Importance of Long-Term Water-Level Data, U.S. Geological Survey Circular 1217. 50 

Winter, Thomas C., J. W. Harvey, O.L. Franke, and W. M. Alley. 1998. Groundwater and Surface Water A Single Resource, U.S. Geological Survey Circular 1139. 51