SPDSS_Task59-1_Develop Locally Calibrated Blaney-Criddle Crop Coefficients

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Information in this memorandum is believed to be accurate. However, information should not be relied upon in any legal proceeding. Approach and Results 1. Gather and Review Appropriate Data and Literature from Previous Lysimeter Studies to Develop Local Blaney-Griddle Crop Coefficients As described in Task 58, the most common means of calculating PCU at high elevations throughout Colorado is by use of lysimeter-derived crop coefficients with the original Blaney- Criddle method (temperature coefficient Kt = 1). Several lysimeter studies for high altitude irrigated grasses/meadow were identified under Task 58. It was originally anticipated that some of the lysimeter studies of interest might present data but not actually provide calibrated coefficients. As described below, calibrated coefficients were developed as part of each study. Therefore, it was not necessary to develop any calibrated coefficients for this task. The following lysimeter studies were investigated for this task: 1. South Park -Leonard Rice Consulting Water Engineers, Inc. (1993) and other consultants have used a pattern of derived crop coefficients for water rights changes cases in South Park. These coefficients are based on a simple averaging of reported coefficients from a number of lysimeter studies. The individual studies evaluated data collected from 1968 through 1970, 1973 through 1974, and 1977 through 1979. 2. South Park - In a report prepared for the Denver Water Board, Walter, Siemer, Quinlan and Burman (1990) evaluated a number of previous lysimeter studies conducted around South Park. Walter et al. developed a set of recommended crop coefficients and compared PCU with those coefficients against measured lysimeter results. The individual studies evaluated data collected from 1968 through 1970, 1974, 1975, 1977, and 1978 through 1979 (note that a number of these studies were also used by LRCWE, 1993). 3. Division 6 Lysimeter Program -This ongoing lysimeter data collection program was initiated in 1978 by Energy Fuels Corporation and subsequently taken over by personnel in Division VI (Division of Water Resources, 2003) in 1983. Lysimeters are principally located in the Yampa River drainage, however a lysimeter was installed in year 2000 in the SPDSS study area near Walden, Colorado. 4. Grand County -Denver Water commissioned lysimeter studies of consumptive use of mountain meadows at high altitudes in Grand County from 1987 through 1990. Results from these studies are reported by Carlson, Pollara, and Le (1991). 5. South Park and Gunnison River Basin -Lysimeter studies were conducted near South Park from 1968 through 1970 and Gunnison from 1969 through 1971 (Kruse and Haise, 1974). Note that the South Park component of this study was reviewed by Walter, et al. (1990). 6. Gunnison River Basin -The Upper Gunnison Water Conservancy District sponsored lysimeter-based investigations of irrigated meadow grass consumptive use from 1999 through 2003 at ten sites in the Gunnison River Basin. This investigation was conducted by Colorado State University (Smith, 2004). Task59_l.doc (updated January 11, 2008) 2 of 32