Laserfiche WebLink
Table 6 <br />Recommended Maximum Application Efficiencies <br />Flood Sprinkler <br />Irrigation Irrigation <br />60% 80% <br />Information from Other Sources -Checks <br />The CSU extension office in Alamosa, as well as county MRCS offices throughout the <br />San Luis Valley, were contacted to determine if they have been involved with, or knew of <br />any, canal loss studies performed on Rio Grande diversion canals. They were not aware <br />of any studies. A literature review was performed to gather additional information <br />regarding conveyance efficiencies in the San Luis Valley, as well as elsewhere. The <br />information gathered was used to check the conclusions suggested in this memorandum <br />for reasonableness. The following summarizes this effort. <br />The 1976 report Crop Consumptive Irrigation Requirements and Irrigation Efficiency <br />Coefficients for the United States, published by the USDA and the SCS, suggested an <br />average conveyance efficiency for the San Luis Valley of 68 percent in 1975. This <br />report did not attempt to distinguish between early season and later season <br />efficiencies. The 68 percent fall in the range of the suggested conveyance efficiencies <br />for the large ditches. The report indicated that conveyance efficiency in the San Luis <br />Valley would likely increase to 75 percent by the year 2000, as canals would be <br />improved or lined. As discussed previously, this has not necessarily been the trend, <br />as aquifer recharge along the canal systems is generally considered to be a benefit, <br />particularly in the Close Basin. <br />This report also indicated that the average application efficiency for 1975 was 54 <br />percent. This efficiency is in the range for flood irrigation efficiency, which is <br />expected because the extensive changeover to sprinkler systems was still on going <br />through the 1970s. The report predicted the application efficiency would increase to <br />60 percent by the year 2000, as more farms moved toward sprinkler irrigation. <br />During the Rio Grande Water Supply Study, Phase I, performed by LRCWE in 1990, <br />a table was obtained from a report done by Zorich-Erker Engineering, Inc. The report <br />(actual title unknown) outlined work they had performed during an investigation of <br />the recharge of the confined and unconfined aquifers in the Closed Basin of the San <br />Luis Valley in 1977. They provided a table of Estimated Annual Recharge to <br />Unconfined Aquifer (Closed Basin) that showed canal losses. A footnote to the table <br />indicated that canal loss figures were "estimated on the basis of the canal loss figures <br />developed for the Farmers Union Canal, with adjustments made for difference soil <br />conditions, amount of water carried and length of canal". This resulted in the <br />following conveyance efficiency figures: <br />- Farmers Union Canal 71% <br />appendB_cropcu_6-2004.doc B-17 of B-19 12/13/00 <br />