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<br />,.., <br />, <br />~. <br /> <br />001428 <br />Summary of Water Resources in Mexico <br /> <br />. <br /> <br />Purpose <br />The purpose of this document is to summarize data and information related to the use Colorado <br />River water in Mexico and to determine where there are data deficiencies that limit our <br />understanding of the Colorado River water budget in Mexico. <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, and flows supporting environmental resources in the <br />Colorado River delta, Cienega de Santa Clara, and Salton Sea was the desired product resulting <br />from this analysis. However, there are few 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 sufficiently current and comprehensive such that a temporal <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 />. Seepage from the All American Canal that is used by Mexico was estimated as 75% of the <br />measured loss between Pilot Knob and Drop 4 (75% of 67,700 acre-feet, or approximately <br />50,000 acre-feet per year). Others have used estimates of up to 100,000 acre-feet per year. <br /> <br />. Estimates of groundwater underflow from the U.S. to Mexico were taken from USBR <br />LCRAS reports (1995 to 2000). <br /> <br />Mexico (CILA. CNA. Rio Colorado Irrigation District. reference material) <br />Insufficient data is available to construct a 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 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 described below: <br /> <br />. With respect to the flows supporting the Colorado River delta, only an estimate can be made <br />based on the difference between the amount of water delivered at the Northern International <br />Boundary and the amount that was diverted 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 the month of June for the years 1984, 1998, and 2000 <br />was performed in an attempt to determine the amount of irrigated acreage in Mexicali and <br />San Luis Valleys, and use the irrigated 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 based 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 satellite imagery for those years and the results of analysis <br />are attached. <br /> <br />SNW A Resources 4/24/02 <br />