SPDSS_Task58_Review Previous Estimates of Potential CU

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SPDSS Task 58 Memo August 5, 2004 Page 11 of 22 4. Lysimeter Studies Lysimeters are containers filled with soil and grass or crops that are located to represent a field environment and are used to determine the evapotranspiration of a growing crop or reference crop. Though most lysimeter results are for limited time periods, these results are generally useful to establish a range of crop coefficients and provide an element of "ground truthing" to consumptive use estimates in an area. Historical or current lysimeter studies identified during our investigations are described below. South Park Five lysimeter studies have been conducted in South Park as briefly indicated below. 1. Near Garo, in 1968, 1969 and 1970 (Kruse and Haise, 1974), these studies were run in conjunction with a lysimeter study at Gunnison in 1969 and 1970. 2. In 1973 and 1974, (Skogerboe and Walker, 1974). Note: Scogerboe and Walter also performed a similar study in the Upper Arkansas River Basin during 1974. 3. 1977 and 1978, Hazen Research set up four lysimeter sites near Hartsel (Berthould and Waldvogle, 1977 and 1979) 4. In 1979, Rice (1981) operated eight disturbed-soil lysimeters planted with sod of native vegetation in support of a change of water rights on the Badger Basin Ranch. 5. In 1981 - 1985, a total of 13 lysimeters were installed at three sites near Hartsel, near Jefferson and east of Fairplay (Walter, Siemer, Quinlan and Burman, 1990). These lysimeter studies in South Park provide a variety of data, some of questionable value, which should be reviewed in the derivation of SPDSS consumptive uses for high altitude irrigated grasses. Division 6 Lysimeter Program The only ongoing lysimeter data collection program in the SPDSS study area we are aware of is a program that was initiated in 1978 by Energy Fuels Corporation and subsequently taken over by personnel in Division 6 (Division of Water Resources) in 1983. Though the lysimeters in this program are principally located in the Yampa River drainage, a lysimeter was installed in year 2000 near Walden, Colorado (in the SPDSS study area). Division 6 uses this lysimeter data to calculate modified Blaney-Griddle crop coefficients and apply those crop coefficients to the estimation of PCU of irrigation water for native grasses. The lysimeter program continues to operate and results through 2003 have been obtained from the Division 6 office. No lysimeter data presently resides in Hydrobase. The results of the Divison 6 lysimter program will be compared to other high altitude grass consumptive use estimates in deriving PCU use for high altitude meadows used in the SPDSS. As an example of the results, measured PCU of pasture grasses at Walden was 26.5 inches on average for the period of 2001-2003.