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PRRIP Governance Committee Meeting and Materials
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PRRIP Governance Committee Meeting and Materials
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Last modified
1/26/2010 4:39:13 PM
Creation date
6/22/2009 12:27:36 PM
Metadata
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Template:
Water Supply Protection
File Number
8461.750
Description
Governance Committee
State
CO
Basin
South Platte
Water Division
1
Author
PRRIP
Title
PRRIP Governance Committee Meeting and Materials
Water Supply Pro - Doc Type
Meeting
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? The Type-of-Year is based on the predicted S1VI (286,000 a fl and Lake McConaughy carry-over <br />contents on October 1, 2007 (468,900 a fl, in accordance with Section III of the EA Document. <br />Predictions for WY08 are slightly less than the actual values for WY07, reflecting anticipated <br />continued record-low inflow conditions. If the WY08 predictions hold true and no EA releases <br />are made, EA content by the end of the September, 2008 will be about 115,000 af (i.e., 10% S1VI <br />+ Carry Over - Evap.& Seepage or 32,600 + 97,633 - 15,000 = 115,233). However, as explained <br />in the sections below, EA releases are planned during WI'08 and these will lower the EA <br />contents accordingly. <br />Prior to WY03, flows at Grand Island were projected and compared to the Service's instream <br />flow recommendations for the purposes of projecting shortages during target flow periods. <br />During drought conditions; however, estimating flows at Grand Island based on the Districts' <br />projected operations, has proven problematic. Shortages were determined from estimates of <br />flows at Overton and Grand Island, using projected Jeffrey and J-2 returns and average river <br />gains/losses. Based on experiences during drought conditions, the use of average gains/losses <br />overestimates flow expected to occur at Grand Island. Using average monthly gains/losses from <br />high loss periods (e.g., 1993-1994) also provide erroneous results. Therefore, a more general <br />description, based on operations and conditions experienced during the drought water years 2002 <br />to 2007, was again used to predict flow conditions for WY08. <br /> <br />Water Year 2008, Projected NPPD Non-Irrigation Season Operations <br />• Due to below-normal water supply forecasts and low Lake McConaughy carry-over storage, the <br />Districts will again follow a conservation mode of operation to maximize the combined storage <br />in Lake McConaughy and Sutherland Project. No releases from Lake McConaughy into the <br />Sutherland Canal at the Keystone Diversion are anticipated except as necessary to provide for <br />icing conditions or to maintain the elevation of Sutherland Reservoir to provide cooling water for <br />Gerald Gentleman Station. At this time, NPPD does not anticipate making releases from <br />Sutherland Reservoir, Lake Maloney, or from the North Platte Hydro during the fall and winter <br />months. Should flows be available from the South Platte River, NPPD anticipates diverting <br />flows for Lake Maloney and Sutherland Reservoir storage if possible. Releases from the North <br />Platte Hydro could occur if South Platte flows are of adequate quantity and duration. <br />Water Year 2008, Projected CNPPID Non-Irrigation Season Operations <br />Under normal and above-normal water supply conditions, CNPPID generally releases sufficient <br />water from Lake McConaughy during the non-irrigation season to divert 1,200 cfs or more into <br />its canal system at the Tri-County Diversion Dam and produce power through its series of power <br />plants along the canal. Under these conditions, diverted water is passed through the hydroelectric <br />turbines and returns to the Platte River near Lexington below the J-2 powerplant with relatively <br />limited fluctuations, and generally in the range of 1,000 to 2,000 cfs. <br />Hydroelectric turbines have a point of peak operating efficiency such that flows above or below <br />this level result in less efficient power generation. Increasingly lower flows subject CNPPID <br />? equipment to undesirable stress, cavitation, and vibration. As a result, under low water supply <br />conditions, CNPPID regulates flow in Johnson Lake and its canal system until sufficient volume <br />is available to operate at higher and more efficient rates, typically in an on-and-off manner over <br />Water Year 2008 EA AOP 8 October 15, 2007
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