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. . . Western States Water Council Full Council Minutes Boise, Id~ho April 22, 2005 WELCOME AND INTRODUCTIONS/APPROVAL OF MINUTES Karl Dreher welcomed members and guests. He also read a welcoming letter from Governor Dirk Kempthorne. Further, Karl thanked CH2M Hill and Clear Springs Foods for sponsoring the field trip and dinner. The minutes of the last meeting in Santa Ana Pueblo, New Mexico were approved as submitted. WATER RESOURCE ISSUES IN IDAHO Karl addressed water resources issues in Idaho, focusing on the crisis on the Eastern Snake River Plain. King's Hill is the demarcation feature between the Eastern and Western Snake Plain; The Aquifer covers an area 60 by 110 miles, comprising 10,000 square miles. It is fractured basalt, several thousand feet thick, with storage approaching a billion acre-feet (at) of ground water. It thins near the edges and spills over a confining layer, discharging through springs. The estimated conductivity is up to 100,000 feet per day. Some 7.5 million acre-feet (Mat) is taken in by the aquifer, including 3.7 Maf of incident recharge mostly from irrigation, 2.2 Maf in precipitation, and about 1.0 Maf of tributary under flow. Near Arco, Idaho the Big Lost River, which originates in the mountains near Mackay, totally disappears into the basalt plain. The Snake River loses some 900,000 to the aquifer annually. The aquifer loses 7.5 Maf of discharge, with 3.8 Maf discharged in the Thousand Springs area visited on the field trip. Another 2 Maf is withdrawn by ground water pumping, and the Snake River gains 1.7 Maf in a reach near American Falls Reservoir. By way of a historical note, American Falls caught the flood from the Teton Dam failure. The Eastern Snake Plain is a "hydraulically connected" surface water and ground water system with exchanges between the sources. There is alluvial ground water flowing into streams, as well as surface water losses to ground water. Since the mid-1800s, surface irrigation on the Snake Plain has contributed to aquifer gains. The Snake River, with 37 Maf flowing, is the largest of the Columbia River tributaries. At one time surface water diversions were around 20 acre feet of water per acre (ac ft/acre). There was some subirrigation, or diversion of enough water to bring the water table up to the root zone, which was a community standard. Crop consumption is only about four acre-feet per acre, so the difference has recharged the aquifer for decades. Water levels rose over the 10,000 square miles some 60-100 feet. Spring discharges nearly doubled by the 1950s. The U.S. Geological Survey (USGS) estimates the 4,200 cubic feet per second (cfs) to be the original discharge base flow, which went up in the 1950s to 6,800 cfs. There are 65 class one springs, with 12 in the Thousand Springs area. 3