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W I. I I I I I I I Ie I I I I I I I. I I separated by shale layers is not the same as a continuous 200-foot thick sandstone aquifer. A primary difference between these two aquifers is the amount of available drawdown which can be placed on the aquifer materials under unconfined conditions. The maximum change in hydraulic head (drawdown) which can be placed on a 20-foot thick sandstone layer is 20 feet. A 200-foot drawdown can be placed on the 200-foot aquifer. A larger amount of groundwater production will be available from the 200-foot aquifer. An additional issue is nonlinearity of specific capacity in an unconfined layered aquifer. Under confined aquifer conditions, specific capacity is constant and there is a linear relationship between pumping rate and drawdown. When unconfined conditions occur specific capacity is no longer constant and the relationship between pumping rate and drawdown is nonlinear. When the groundwater level is below the base of a layer, unconfined sandstone layers will drain into a well independently of the pumping water level in the well. Flow into the well from unconfined layers will be based on the hydraulic conductivity and the hydraulic gradient of the sandstone layers. The economic life of the aquifers should be analyzed as an aquifer drawdown problem where the relationships among aquifer drawdown, the pumping water level in a well, and production from a Denver Basin aquifer well are all taken into account. The problem can be stated as follows: How does production from the Denver Basin aquifers change in response to reduced saturated thickness and lower pumping water levels? Well pumping rates are important because they are the measure of an aquifer's production. Additionally, the costs of well installation, operation and maintenance over time to maintain aquifer production will be included in the economic analysis. 2 HRS WATER CONSULTANTS, INC.