Exec Summary Report_11-15-04 - Laserfiche WebLink

Home Browse Search

Executive Summary 5. Increased Reliance on Nonrenewable, Non-tributary Groundwater for Permanent Water Supply Brings Serious Reliability and Sustainability Concerns in Some Areas, Particularly Along the Front Range The state's aquifers are a valuable water resource that is under increasing pressures for development. Recent court cases have heightened the scrutiny of groundwater use, while the drought of 2002 has highlighted the physical constraints to continuous pumping of some regional aquifers. These challenges, when coupled with a complex hydrology, point to groundwater as an area for ongoing concern as a source of water supply. Much of Colorado is underlain by abundant groundwater but its use as a water supply is limited in many areas by the physical or the legal constraints on the aquifer supplies. Either limitation affects the reliability and sustainability of groundwater as a source of supply. The physical availability is the amount of water an aquifer can produce, in both the short- and long-term, and primarily affects the sustainability of the resource. The legal availability is the amount of water that can be extracted from an aquifer under the water rights administration system that exists in a particular area, and can affect the reliability of the supply. Economic constraints associated with higher pumping costs may also limit the development of these supplies. Although an aquifer may be capable of producing water reliably under varying climate conditions (wet and dry years) for many decades, if it is not replenished by renewable supplies and if demands on it are too high it would not be considered a sustainable resource. Increased demands combined with the drought since the late 1990s have resulted in declining groundwater levels in several regions and a forced reduction in use and tighter regulation of wells in some areas. Together, these events call into question the overall sustainability and reliability of many of the largest groundwater supplies, and suggest that our understanding of these supplies and their uses needs to be improved. Colorado is fortunate to contain a variety of aquifers that are present in virtually every county. Whether the water is drawn from a shallow alluvium to irrigate crops or lifted 1,500 feet from deep bedrock to supply suburban homes, the favorable economics of groundwater development has become integral to the growth of our state. Aquifers in the state range from those in the shallow unconfined alluvial sediments along the major river systems to the deeper confined aquifers in many of the bedrock deposits. The mountain areas also contain groundwater in fractured bedrock that is highly variable in amount and distribution. Unfortunately, many of these aquifers have a limited ability to supply usable and sustainable quantities of water. This is due to several factors including: their limited size, aquifer composition that does not allow it to readily yield water, and/or because the aquifer is not replenished quickly enough by external sources of water. The bedrock aquifers in particular have very limited and very slow natural recharge. Their supplies are typically not tributary to surface water sources and for all practical purposes are a non-renewable resource. Groundwater use is widespread and comprises almost 20 percent of the total water used in Colorado. As shown in Figure ES-12, groundwater use is a significant portion of overall water use in the South Platte, Arkansas and Rio Grande River Basins. Due to the methods used to report water use, it is possible that groundwater use is underestimated and could represent a larger proportion of water use than shown on Figure ES-12. Figure ES-13 identifies the dominant use of groundwater for each County in the year 1995, even though the total amount of groundwater used in many areas might be small. Statewide, agriculture makes up about 90 percent of all groundwater withdrawals. ~ $~ole'ri~ice Wo~e' $upplY Initia~ive ~~ S:\REPORT\WORD PROCESSING\REPORT\EXEC SUMMARY 11-10-04.DOC ES-23