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The overall view of the Denver Basin Aquifers also reveals a complex combination of water use and resource protection, The Denver Basin Aquifer system consists of the Dawson (upper and lower), Denver, Arapahoe (upper and lower), and Laramie-Fox Hills aquifers, The aquifers cover an area of about 6,700 square miles extending from Colorado Springs on the south to Greeley on the north, and from the foothills on the west to Limon on the east (Figure 1 and 2), The Aquifer system contains approximately 300 million ac-ft of drainable storage, To put this quantity of water in perspective, this amounts to a reservoir 15 times greater than the active storage of Lake Powell (20 million ac-ft) , and 400 times greater than the active storage of Blue Mesa Reservoir (750,000 ac-ft) , The estimated total pumping of groundwater from the Denver Basin Aquifers in 1996 was 56,000 ac-ft, This is less than 2% (60,000 ac-ft) of the 1 % (3,000,000 ac-ft) annual allowable pumping quantity under the 100 year aquifer life administration criteria provisions of Senate Bill 85-5, Eventhough some localized well pumping drawdowns and loss of hydrostatic pressure are occurring, the overall Denver Basin aquifer life at this level of production (56,000 af/yr) may exceed 1000 years, Simplified projections of well development and population growth to the year 2100 result in groundwater production estimates of abc'J! 300,000 ac-ft per year which is about 10% of the annual allowable pumping from the Denver Basin aquifers under the 100 year aquifer life assumption, Depending on unknown future conditions, this amount could be significantly different. The impacts to South Platte River flows and the potential injury to senior water rights due to depletions from ground water pumping are not currently evident due to the net increased flow in the South Platte from Denver Basin aquifer return flows and due to the delayed impacts of pumping. Therefore, water policy decisions related to the long- term use of this nonrenewable resource and the management of the South Platte River are not immediately critical. However, these water policy issues must be addressed over the next few years through the development and use of advanced computer modeling, improved data bases and a more thorough understanding of all the potential causes of injury to senior water rights on the South Platte prior to changing existing statutes. II, Public Water Policy Issues This study has raised a number of water policy issues that must be addressed through additional study and public meetings, and by the legislature acting in its role as "decision maker" in public water policy, The water needs of the Denver metropolitan area and South Platte River basin are increasing as a result of population growth. Water for this increasing population will come from a combination of six sources: 1) Water conservation 2) Water reuse 3) Trans-basin imports 4) Conversion of in-basin agricultural water - 2- I I I I I I I I I I I I I I I I I I I