EF Escalante Creek Appendices - Laserfiche WebLink

Home Browse Search

Table I: Data Partv USFS USFS Date 06/04/2004 06/04/2004 Q 4.45 4.31 250%-40% 11.1 - 1.8 10.8 - 1.7 Summer(3/3) 4,9 2.8 Winter (2/3) 1.2(1) 1.1 (I) BLM Bureau of Land Management DOW - Division of Wildlife (1) Predicted flow outside of the accuracy range of Manning's Equation. USFS - United States Forest SelVice ? = Criteria never met in R2CROSS Staging Table. Biologic Flow Recommendation The summer flow recommendations, which meet 3 of 3 criteria and are within the accuracy range of the R2CROSS model, range from 4.9 cfs to 2.8 cfs (See Table I). The winter flow recommendations, which meet 2 of 3 criteria but are outside the accuracy range of the R2CROSS model, range from 1.2 to 1.1 cfs (See Table I), Averaging the two summer flow recommendations within range results in a 3.9 cfs recommendation. Averaging the two winter flow recommendations outside the range results in a 1.2 cfs recommendation. It is our belief that recommendations that fall outside of the accuracy range of the model, over 250% of the measured discharge or under 40% of the measured discharge may not give an accurate estimate of the necessary instream flow required. In these cases, CWCB staff relies upon the biological expertise of the cooperating agencies to develop a biologic instream flow recommendation. The USFS has indicated that this is a high priority stream segment to them, however, because the winter recommendation falls outside the accuracy range of the R2CROSS model, staff has consulted with the recommending agency. Staff and the recommending agency believe the winter flow recommendation of 1.2 cfs would be appropriate for the Board to file on (See Table I). Hydrologic Data After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted an evaluation of the stream hydrology to determine if water was physically available for an instream flow appropriation. The hydrograph below was derived from data collected by the USGS stream gage for Escalante Creek near Delta, CO (10 #09151500), which has a drainage area of 209 square miles (See Gage Summary in Appendix C). The total drainage area of this segment of the East Fork Escalante Creek is approximately 25.7 square miles. The period of record for this gage was 1976 to 1989, the period of record used by staff in their analysis was 1976 - 1989, or 14 years of record. Since this gage is heavily impacted by upstream diversions, the estimated average flow was derived by adding average diversion records for the irrigation season (March through October). Table 2 below displays the estimated average flow of East Fork Escalante Creek. Table 2: Estimated Stream Flow on East Escalante Creek: Jan Feb Mar Apr May Jun efs 1.5 1.7 2.7 16_0 35.4 4.0 Jul 1.2 Aug Sep 1_1 1_3 Oct Nav Dee 1_6 1_7 1.4 -4-