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of cropland constitutes the lazgest of these uses. Surface water consumed within the Yampa River drainage basin in 1976 totaled approximately 445,000 acre-feet. Of that, 399,000 acre-feet were used for irrigating croplands and hay meadows or for watering livestock. Other uses included 5,478 acre-feet for industrial purposes, 2,555 acre-feet for municipal water supplies, and 8,283 acre-feet for other unspecified uses (Steele et al., 1979). Industrial consumption has since increased by a total of 18,720 acre-feet per year due to use by the Craig generating station. Irrigation Use of Surface Water. Water for agricultural irrigation is generally obtained by simple stream diversion structures and networks of ditches for flooding grasslands and meadows during summer months. The short growing season precludes growing of warm weather crops such as com. In the Williams Fork River, an even higher proportion of the water used is for imgation of grasslands and hay fields. Aquifer Stratigraphy. Within the general vicinity of the Eagle Mines, ground water exists in both bedrock and alluvial aquifers. Significant bedrock aquifers aze (listed in ascending stratigraphic order) the Trout Creek, Middle, Twentymile, and White sandstones. The Middle, Twentymile and White sandstones aze in the Williams Fork Formation; the Trout Creek sandstone is the uppermost member of the underlying Iles Formation. The main alluvial aquifers in the azea aze associated with the Yampa and Williams Fork Rivers. The alluvial aquifers probably contribute to baseflow of the rivers during dry periods. Coal seams, discontinuous sandstones, and siltstones and smaller alluvial bodies in the area of the mine are also water- bearing, but contain insufficient quantities of water to be considered significant aquifers. Ground Water Use. The Trout Creek Sandstone, the Twentymile Sandstone, and the White Sandstone aze bedrock aquifers currently being used for ground water supplies in the general vicinity of the Eagle Mines. The Middle Sandstone is not currently used as a ground water supply in the vicinity. The alluvial bodies associated with the Yampa River and Williams Fork River contain limited ground water and are not considered major aquifers in the general azea. Alluvial bodies along the Yampa River up- and downstream of the general azea, however, aze significant sources of ground water. High yield irrigation and municipal water supply wells aze completed in the Yampa River alluvium in those azeas. Also, the Yampa River alluvium outside the vicinity is widely used as a source of domestic and livestock watering. Within the vicinity, alluvial ground water is not a significant source of water put to beneficial use. Ground water from the coals and thin sandstones are not considered aquifers, but they flow into the underground workings and the mine uses them for cooling, dust suppression, fire protection, and other industrial uses. Ground Water Recharge, Discharge, and Flow. The sandstone aquifers in the Big Bottom Synclinal Basin are rechazged at their subcrops beneath the stream/alluvial systems of the Yampa and Williams Fork Rivers, and at their outcrops in upland azeas, From a recharge area, flow would be generally northward, downdip toward the axis of the Big Bottom syncline. Faults may provide conduits of flow for ground water wherever a fault is not sealed with fine-grained gouge material. Ground Water Hydraulics. The sandstone aquifers aze under atmospheric pressure (water table conditions) neaz their rechazge azeas and under hydrostatic pressure (artesian conditions) within the structural basins or at discharge points. Hydrostatic pressures in the sandstone aquifers 7