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, . STATE f)F COLORADO - Colorado Water Conservation Board Department of Natural Resources 721 Centennial Building 1 31 3 Sherman Street Denver, Colorado 80203 Phone: (3031 866-3441 fAX, (3031 866-4474 Roy Romer Governor J.lmes S. Lochhead Executive Director, DNR Dilries C. tile, P.E. Director, ewes Mareh 20, 1998 Roy Smith Instream Flow Coordinator Bureau of Land Management 2850 Youngfield Street, Mail = CO-932 Lakewood, CO 80215 Subject: Trout Creek Water Availability Study and ISF Recommendations. Dear Roy: CWCB staff reviewed the BLM field data, the Trout Creek Synthetie Hydrograph derived utilizing methods outlined in the USGS Water Resourees Investigations Report 85-4086 and stream flow data from the USGS gages loeated on Coehetopa Creek below Roek Creek near Parlin (ID# 09118450) and the Lake Fork of the Gunnison at Gateview (ID# 09115500). Trout Creek - headwaters to Johnson Diteh head gate Aeeording to gage reeords for Coehetopa Creek, the flow reeorded at this gage on August 6, 1996, was 14 efs or 46 efs below the August monthly median or 23% of the median. Likewise, aeeording to gage reeords for the Lake Fork, the flow reeorded at this gage on August 6, 1996, was 120 efs or 51 efs below the August monthly median or 70% of the median. The Trout Creek drainage basin is smaller than both of these drainages. This eompiled with the August 1996 Gunnison River Surfaee Water Supply Index Value of -0.7 (attaehed), indieates that basin water supplies were below normal to well below normal at the time of the BLM field survey. The BLM measured 0.36 efs on August 6, 1996, within this reaeh of stream and aeeording to the SEa's Water Rights Tabulation the upstream diversions total 10.9 efs. The synthetie model predieted the mean monthly flow for August to be between 2.9 and 10 efs, with the average being approximately 6.5 efs. The synthetie model eorresponds extremely well with the basin area apportioned averages assoeiated Lake Fork gage readings. Based on the data above the CWCB feels the average flow for August is approximately 6.5 efs or 100% of the average flow predieted by the synthetie model. However, we feel the lower terminus of the Trout Creek ISF reaeh should be moved to the Johnson Ditch Headgate. Based on this reduction staff determined the following stream flows are available for appropriation for the Trout Creek ISF reaeh: