PRRIP Governance Committee Meeting and Materials

Home Browse Search

? April is used in assigning 10% of the S1VI to the EA. These predictions establish certain reservoir operating rules during the non-irrigation season (see Appendix B, pages 20-21). The EA Manager is notified by the Districts of any modification to the predictions that would result in a change in the Type-of-Year. When practicable, the Districts have also provided projections for flows at Overton and Grand Island, based on their predicted operations, to assist the EA Manager in developing the EA AOP. The Districts' predictions for SNI and Type-of-Year for the 2007 water year and the actual water volumes were as follows: Item Prediction Actual % of Predicted SNI, October through March 295,000 af 289,810 af 98.2% SNI, October through April 340,000 af 328,030 af 96.5°/a Type-of-Year Very Dry Based on anticipated below average carry-over storage in Lake McConaughy and water supply on the North Platte, the Districts' 2007 Water Year Operation Plan again called for maximizing storage while meeting their minimum operational flow requirements. During the 2007 water year (WY07), non-irrigation season inflows into Lake McConaughy were again well below normal. Appendix G-Figure 1(page 42) illustrates Lake McConaughy inflow for a portion of calendar year 2007 compared to historic conditions. • Inflow measured at the Lewellen river gage on June 25, 2007 was only 84 cfs, or 4.5 percent of the average June 25 measurement (1,866 cfs) since storage began in 1941. During May and June, the time of year when inflows are typically at their highest, inflows to Lake McConaughy averaged 388 cfs, or 22 percent of the May-June average of 1,780 cfs since 1941. On May 1, 2007, Lake McConaughy was four feet lower than it was on May 1, 2006. Total storage was 733,500 af on May 1, 2006, and 663,633 af on May 1, 2007. However, precipitation below the lake raised stream flows and enabled CNPPID to delay irrigation releases for several weeks. As a result, the contents at the end of June, 2007 (664,854 afl were about three feet higher than it was at the end of June 2006. Precipitation in the Platte River valley also made it possible far CNPPID to divert excess river flows into Elwood Reservoir, adding more than 15 feet to the lake's water level. CNPPID received permission from the NE Department of Natural Resources to divert water from the Platte River into the reservoir over the course of several days in June when flows exceeded existing NE instream flow water rights and target flows used in the Nebraska New Depletion Plan (PRRIP, Attachment 5, Section 8). In response to low water supplies at Lake McConaughy, CNPPID's irrigation customers were limited to 6.7 inches/acre in 2007 over an eight-week season. Normal deliveries are 15 to 18 inches/acre over 12 weeks. Although the lake ended this year's irrigation season about six feet higher in elevation and held 104,700 acre-feet more than last year, inflows to the lake were the fifth lowest on record. The four lowest inflow yeaxs have occurred since WY02. Lake ? McConaughy contents at the end of WY07 were 468,900 af. Water Year 2008 EA AOP 3 October 15, 2007