Kansas Geological Survey, Public Information Circular (PIC) 9
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Sustainable development is broadly defined as development of a resource that meets the needs of the present without compromising the ability of future generations to meet their own needs. In this circular, sustainable development of water resources refers to a holistic approach to development, conservation, and management of water resources, an approach that considers all components of the hydrologic system. This concept requires that, in the long term, a balance must exist between the amount of water entering and the amount leaving the system. In other words, discharge to streams, springs, and wetlands (and pumping) must equal recharge, and ground water and surface water must be considered together.
To protect ground-water supplies from overdevelopment, some state and local agencies have enacted regulations and laws based on the concept of safe yield. Safe yield is defined as the attainment and maintenance of a long-term balance between the amount of ground water withdrawn (pumped) annually and the annual amount of recharge (Sophocleous, 1997). Safe yield is a management concept that allows water users to pump only the amount of ground water that is replenished naturally through precipitation and surface-water seepage (recharge). As defined, safe yield ignores natural discharge from the system.
As stated earlier, under natural conditions, recharge to an aquifer is balanced by discharge. Consequently, if pumping is allowed to equal recharge, the streams, marshes, and springs will eventually dry up, because pumping removes the water that would otherwise be discharged naturally. Clearly, limiting water use to the amount of natural recharge is not enough. Nonetheless, this so-called safe yield concept is still mistakenly viewed as sustainable management.
Ground-water pumping in the last 50 years has depleted parts of the High Plains aquifer especially in southwestern Kansas, where water levels have dropped as much as 200 feet (61 m) in some places. These declines in the saturated thickness of the aquifer (fig. 3), especially in western Kansas, prompted the Kansas Legislature to pass the Kansas Groundwater Act in 1972, authorizing the formation of local ground-water management districts (GMD's) to help direct the development and use of ground-water resources. Since passage of the act, five districts have been formed (fig. 4).
Figure 3--Percent change in saturated thickness (predevelopment through 1996) of the High Plains aquifer in western and central Kansas (adapted from Sophocleous, 1997b).
Figure 4--Ground-water management districts in Kansas.
The three western districts (GMD's 1, 3, and 4) overlie all or parts of the Ogallala aquifer and have the greatest number of large-capacity wells and the highest rate of water-level declines, while having the least precipitation and ground-water recharge. Each of these districts has adopted a plan that will allow a portion of the unappropriated aquifer to be depleted (no more than 40%) over a period of 20 to 25 years (planned depletion policy), implying that the Ogallala is not a renewable resource, at least within a human generation. This plan applies only to appropriations that were established since the policy was adopted in the late 1970's. By 1990, GMD 4 had switched to a zero depletion policy, for new wells only. Under zero depletion, an established average water level is maintained, regardless of the recharge rate.
In the late 1970's and early 1980's, GMD's 2 and 5 in central Kansas, which receive more precipitation (and thus more ground-water recharge), initially adopted the traditional safe-yield approach to ground-water management. According to this policy, the total amount of water that could be appropriated was limited to the long-term annual recharge, implying a renewable ground-water resource. This was the first endeavor in the state to manage ground water as a renewable resource.
Because of declines in ground-water levels, streamflows in western and central Kansas have been decreasing, especially since the mid-1970's. In response to these streamflow declines, the Kansas Legislature passed the minimum instream flow law in 1982, which requires that minimum desirable streamflows be maintained in different streams in Kansas. Although the establishment of minimum desirable streamflows was a major step toward conservation of riverine habitat within the state, streamflows have continued to decline (Ferrington, 1993). Maps comparing the perennial streams in Kansas in the 1960's to those of the 1990's show a marked decrease in miles of streamflow in the western third of the state (fig. 5).
Figure 5--Major perennial streams in Kansas in 1961 and 1994 (adapted from Angelo, 1994).
As a result of continued declines in ground-water levels and streamflow in parts of GMD's 2 and 5 during the 1980's, both GMD's re-evaluated their safe-yield policies and regulations in the early 1990's. Beginning in 1994, these GMD's changed to conjunctive management of stream-aquifer systems by enhancing their existing safe-yield policies to include the natural ground-water discharge to streams (baseflow) when evaluating a ground-water permit application. The new regulations moved towards a sustainable-yield approach, but for regulatory and name-recognition purposes, GMD 2 continues to refer to them as safe yield, whereas GMD 5 changed theirs to sustainable yield. Both districts are monitoring the effect of the enhancements.
Policymakers, water regulators, and water users have come to realize that ground water and surface water are closely interrelated systems. Ground water feeds springs and streams, and surface water recharges aquifers. The interactions of ground and surface water affect quality as well as quantity. Ground water can be contaminated by polluted surface water, and surface water can be degraded by discharge of saline or other low-quality ground water. Streams and their alluvial aquifers are so closely linked in terms of water supply and water quality that neither can be properly understood or managed by itself, and therefore the combined stream-aquifer system must be considered.
The Division of Water Resources, Kansas Department of Agriculture, is attempting to develop a comprehensive management program in areas of Kansas with significant water problems. Working within the framework of existing state laws, this program intends to develop proactive, long-term solutions, which take into account surface-water depletions, ground-water declines, and deterioration of the water quality. This holistic approach (referred to as the watershed-ecosystem approach) recognizes that streams are the products of their drainage basins or watersheds and their associated aquifers, not simply water flowing through a channel, and that to understand such stream-aquifer interactions, it is necessary to understand the surface- and ground-water watersheds associated with the stream. Close consultation and cooperation with the local GMD's, irrigators' associations, and other interested parties are integral parts of this program.
Management of the ground water and surface water of a watershed or drainage basin using the ecosystem approach is beginning to take hold in Kansas. The evolution of Kansas water-management policy away from the traditional notion of safe yield is an important first step toward the sustainable development of water resources in Kansas.
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Kansas Geological Survey, Public Outreach
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Web version February 1998