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<br />I <br />t4" <br /> <br />OD1441 <br /> <br />Summary of Water Resources in Mexico . <br /> <br /> <br />Pumo~ ! <br />The purpose of this document is to sUI111llarize data and information related to the use Colorado <br />River water in Mexico and to detenrline where there are data deficiencies that limit our <br />understanding of the Colorado River wat~r budget in Mexico. <br /> <br />,/ <br /> <br />Discussion <br />A water budget for Mexicali and San Luis Valleys that would identify and quantify the water <br />resources, consumptive uses, exports, ~nd flows supporting environmental resources in the <br />I <br />Colorado River delta, Cienega de Santa Clara, and Salton Sea was the desired product resulting <br />from this analysis. However, there are f6w actual data related to these variables. The following <br />are observations related to data availability, quality, and usefulness with respect to compiling the <br />water budget as described above: <br /> <br />U.S. (lBWC, USBR, USGS) <br />· Data from these sources is sufficieRtly current and comprehensive such that a temporal <br />I <br />analysis of the U.S. deliveries to Mexico and drainage water from the Wellton-Mohawk <br />Irrigation and Drainage District could be performed. <br /> <br />. <br /> <br />Seepage from the All American Canal that is used by Mexico was estimated as 75% of the <br />measured loss between Pilot Knob a~d Drop 4 (75% of 67,700 acre-feet, or approximately <br />50,000 acre-feet per year). Others hav~ used estimates of up to 100,000 acre-feet per year. <br />I <br /> <br />Estimates of groundwater underfl01 from the U.S. to Mexico were taken from USBR <br />LCRAS reports (1995 to 2000). <br /> <br />. <br /> <br />I <br />i <br />Mexico (CILA, CNA, Rio Colorado Irrigation District, reference material) <br />Insufficient data is available to construct ~ meaningful water budget for Mexico for the purposes <br />described above. Available data is piecemeal and generally an estimate. Although some data is <br />reported as an annual value, most of the I data is without temporal scale making it exceedingly <br />difficult to correlate U.S. deliveries with consumptive use and groundwater production in <br />Mexico. Some of the limitations are desctibed below: <br />I <br /> <br />· With respect to the flows supporting t~e Colorado River delta, only an estimate can be made <br />based on the difference between the ainount of water delivered at the Northern International <br />I <br />Boundary and the amount that was qiverted at Morelos Dam, plus estimated agricultural <br />drainage from the Rio Hardy and Rio Pescaderos. There are no stream gages installed on the <br />River or the agricultural drains to substantiate any estimate of flow. <br /> <br />· An analysis of satellite imagery for Je month ofJune for the yeaTs 1984, 1998, and 2000 <br />was performed in an attempt to deterrhine the amount of irrigated acreage in Mexicali and <br />San Luis Valleys, and use the irrigate4 acreage to calculate a consumptive use demand. The <br />analysis was conducted by performing; a natural color analysis of the imagery and grouping <br />the colors into 15 classifications basetI on observations (i.e. roads, urban centers, irrigated <br />lands, etc.). The analysis yielded fewer~ irrigated acres than that reported by the Rio Colorado <br />Irrigation District and CNA. The satell;ite imagery for those years and the results of analysis <br />are attached. I <br /> <br />SNW A Resources 4/24/02 <br />