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I I. I . I I I I I I Ie I I I I I I I. I I Previous work by Robson (1987) and others in the Denver Basin has indicated that estimates of groundwater production are a source of error in the analysis of the Basin's groundwater resources. Robson (1987) states that the Denver Basin aquifer production estimates used in his modeling work are accurate within a range of plus or minus 20 to 30 percent. In his 1987 report, he determined that for the period 1958 to 1978, that total pumping in the Denver Basin aquifers was equal to 3.5 to 4.5 times municipal pumping. It is not known if this factor between municipal pumping and total pumping is currently accurate. In addition to annual pumping data, it would also be useful to have more data on: maximum pumping rates, monthly production volumes, static water level measurements at various times, pumping water level measurements, and aquifer properties of transmissivity, hydraulic conductivity, and storage coefficient. Groundwater production and hydrogeologic data have been surveyed in this Phase 1 study to determine whether or not the results of previous modeling work can be considered as valid for the purpose of evaluating the economic life of the aquifers. The conclusions of this survey are that a limited amount of data is available on Denver Basin aquifer well pumping and that the accuracy of existing estimates is questionable. The derivati9n of new production estimates is beyond the scope of this study. Well production estimates used by Robson (1987) and Banta (1989) at specific aquifer locations will be analyzed. Well production rates used in the economic analysis may be altered to reflect site-specific aquifer conditions. 3.2 Groundwater Level Data Some owners of fee wells maintain static and pumping water level records since this is a method of tracking well efficiency and expected water well work. It should be possible to obtain some of this data if required in Phase 2. Groundwater level data is seldom available for domestic wells except when the wells are drilled or replaced. The best information on Denver Basin aquifer groundwater levels is compiled by the State Engineer's Office. Groundwater level data has been obtained and published on an annual basis since 1987. 4 HRS WATER CONSULTANTS, INC.