Summary

Description

Recharge of the shallow waterbearing beds takes place all along the stream. On the other hand, recharge of the deep pervious beds is inferred to take place largely within 5 miles from the head of the alluvial fan near Burns, where clean gravel and sand form about 90 percent of the fill. Farther from the head of the fan, confining beds prevent recharge of the deep pervious beds by downward percolation. From several lines of evidence it is estimated that the average annual recharge along the Silvies River is about 40,000 acrefeet, of whicn about 6,500 acrefeet could be pumped perennially from wells. In additon some water might be salvaged from the shallow pervious beds by growing alfalfa as a groundwater plant. The water in the bedrock appears to fall into three distinct temperature ranges slightly thermal water, 52 to 62 F.; water of intermediate temperature, 64 to 82 F.; and hot water, 90 to 154 F. The slightly thermal water has been encountered in bedrock wells of moderate depth in the northern part of the basin, where the safe yield of the aquifers appears to be at leart equal to the safe yield of the valley fill. The water of intermediate temperature issues from relatively large springs in three small districts in the west half of the basin; the aggregate discharge by these springs in 1931 was about 40 secondfeet. Water of intermediate temperature also issues from several flowing wells in the vicinity of the springs. The hot water issues from a few springs that are widely scattered over the basin, and their aggregate yield in 1931 was about 5 secondfeet. It issues also from a deep flowing well in the southwestern part of the central alluvial plain. With few exceptions the thermal springs and the flowing thermal wells occur along or very near faults that cut the Tertiary rocks. Six wells more than 500 feet deep have been drilled in the central plain in search of flowing water. The single deep well that was flowing in 1931 suggests that the artesian head is not large.