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-az- water quality is cumulatively impacted, then the alluvial water quality will also be impacted in a similar way. However, the water quality degradation in the alluvial aquifer would probably not represent as significant of an impact as the surface water quality degradation. Prior to mining, the water quality in the aquifers was suitable for irrigation and stock watering purposes and marginal far domestic uses. The expected water quality degradation in the alluvial aquifers would probably not limit uses from what they were prior to mining. Surface Water In January of 1983, the Colorado District of the U.S. Geological Survey, Water Resources Division, was contracted by the Division to model the cumulative effects of all anticipated mining in the general area ofa the Foidel Creek Mine. The USGS adapted an existing surface water quality model for use in this area, and calibrated the model using data from water years 1976 to 1981. The Division provided estimates of the short-tens and long-term effects of mining which were added to the model to predict the cumulative effect of mining in the general area. Model output (monthly discharge, dissolved solids concentration, and dissolved salt load) was obtained for four geographical location; lower Middle Creek, lower Fish Creek, lower Trout Creek, and the Yampa River at the Hayden gaging station. The effects of mining prior to 1981 were included in the USGS data used to calibrate the model. Therefore, the effects of mining after 1981 needed to be estimated and specifically added to the model. These effects were estimated by the Division using information obtained from the mine pernit applications on file with the Division. Scenarios were developed which included both the direct and indirect surface water effects. (Indirect surface water result from the interaction of surface water with affected ground water systems.) Mining effects were divided into short-term effects and long-tens effects. These timeframes are relative. Short-tern effects include surface and ground water effects that would occur during the mining operation and for a short time following reclamation, such as discharge from sediment ponds, discharge from underground mine workings, and the discharge of affected waters from shallow ground water systems. The natural flow patterns of the affected ground water systems is disrupted by mining, and surface and ground water is mixed. Increased evaporation losses from the sediment ponds are assumed to be offset by increased runoff from disturbed areas. The long-term effects of mining are effects occurring after disturbed areas have been successfully reclaimed. The surface and ground water systems have had sufficient time to equilibrate, sediment control structures have been removed and the quantity and quality cf runoff from the reclaimed areas has returned to pre-mining conditions. Spoils aquifers and underground mine workings have resaturated, and ground water passing through the disturbed area discharges in its pre-mining disturbed areas. The quantity of ground water flows would equal pre-mining quantities, but its quality would be degraded.