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<br />'r! ' <br />ct,;;'L ~ <br /> <br />'Rio Grande Compact <br />The central core of constraints in the model allOCates annual streamflow among the states in accordance with the Rio Grande <br />Compact; any examination of institutional adjustments to mitigate the effects of drought will be made within this framework. <br />The important management nodes are the gauging stations at Del Norte, Mogote, Lobatos, Otowi, and Elephant Butte, <br />Equations have been estimated that equal the look-up table values that define annual stream flow allocation listed in Article ill <br />and the Resolution of 1948 of the Rio Grande Compact. For modeling purposes, the annual streamflow requirement at Elephant <br />Butte is met at the inflow rather than the outflow as required by the Compact because of the difficulty in specifying the <br />mathematical equations incorporating total outflows and changes in storage, This change was discussed with Don Lopez, <br />Assistant New Mexico State Engineer, who felt that the change closely approximates Compact requirements, <br /> <br />'1906 Treaty with Mexico <br />This model will meet the requirements of the treaty as specified in Article II. One issue is the statement that "In case, however, <br />of extraordinary drought ... the amount delivered to the Mexican Canal shall be diminished in the same proportion as the water <br />del ivered to lands under said irrigation system in the United States." Extraordinary drought has not been defined, so Dr, Charles <br />DuMars will attempt to clarify the point at which deliveries may be reduced. <br /> <br />'Stream Flows <br />Stream flows are modeled as a simple mass balance: The flow at any node is the flow at the upstream node minus the <br />diversions at the upstream node plus the inflow at .the current node plus or minus any gains or losses between nodes. These <br />gains and losses represent such things as evaporation. changes in bank storage. or infiltration through the stream bed. The, <br />structure is in place; however, parameter values need to be estimated. <br /> <br />Because of federal legislation regarding endangered species, one question that must be addressed is the issue of the Rio Grande <br />Silvery Mill1]ow. Minimum streamflows in the region between Albuquerque and Elephant Butte may be required. An issue of <br />contention will be whose surface water allocation is reduced to maintain that flow. This will be another area in which Charles <br />DuMars will playa significant role. <br /> <br />'Ground Water <br />To date, parameters for ground water pumping have not been developed. Phil King is responsible for providing aquifer <br />parameters. Variables have been entered into the structure, but there are no constraints to limit ground water pumping. There is <br />also a variable that defines injection into aquifers; this is important for EI Paso and may be a future policy option for <br />Albuquerque. <br /> <br />'Economic Benefits <br />Mathematical equations relating economic benefits to alternative levels of water supply are being developed for all uses of <br />water for each of the relevant nodes. These so-called "benefit functions" are designed to reflect foregone economic values for <br />different degrees of drought. These include agriculture, municipal and industrial (M&I), electric power, and recreation. <br /> <br />M&I benefits functions have been developed by Dr. Tom McGuckin. Currently they are expressed on an annual basis, so they <br />must be modified to fit the monthly time step of the model. <br /> <br />Recreational benefits for instream and lake recreational benefits will be estimated by Dr. Frank Ward and will be based on <br />recreational values of streamflow and reservoir storage. Data will be obtained for fishing and other water-based recreation from <br />previous regional studies. <br /> <br />Agricultural benefits will be based on representative farms for each agricultural node. Dr. Grant Cardon at Colorado State <br />University is developing yield functions for various crops which show the effects of water shortages on crop yields. These yield <br />functions will be calibrated to tit conditions for irrigated agriculture in the three states. Drs. Ron Lacewell and John Ellis at <br />Texas A&M are responsible for applying the functions for agriculture in the EI Paso area. Dr. Phil King is responsible for New <br />'''lexico agriculture. These functions are based on the timing of water applications, soil characteristics, and climatic conditions. <br /> <br />:-Iydroelectricity generation and benefits equations have been entered into the model for the three reservoirs that have generating <br />facilities. <br /> <br />5 <br />