The relative importance of ground-water and surface-water supplies to oil-shale development, Piceance Basin, Colorado

Abstract

A sensitivity analysis was perfomed of the required active storage capacity (VMAX) of a hypothetical reservoir on the White River to different assumptions about water demands for oil-shale development and the contributions from various sources of water. Estimates of VMAX were found to be sensitive to estimates of the supply of water available from the oil-shale aquifers. For example, the current estimate of average natural recharge to the oil-shale aquifers is approximately equal to the amount of water required by an oil-shale industry producing 250,000 barrels of oil per day and requiring 3 barrels of water per barrel of shale-oil produced. Estimates of VMAX were also sensitive to estimates of the supply of water available from the Colorado River and the requirements for downstream releases on the White River. The sensitivity of VMAX to use of water from the four main streams in the Piceance basin (Parachute, Roan, Piceance, and Yellow Creeks) was less than its sensitivity to these factors. Compared to the uncertainty in other factors, water-supply estimates are shown to be insensitive to uncertainty in evaporation estimates. A transient analysis was performed using a synthetic streamflow model to generate 500 equally likely periods of monthly inflows to the hypothetical reservoir. An oil-shale industry was assumed to expand from 0 to 1 million barrels of oil per day over a 30-year time period, and mine water was assumed to be available at an increasing rate that averaged one-half the current estimated natural recharge rate to the Piceance basin. Use of this mine water to supply part of the water demand resulted in reductions in surface-storage requirements (VMAX) on the order of 15-20 thousand acre-ft over many of the 500 streamflow sequences. (USGS)