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<br />Methodologies for Estimating and Projecting Urban (Municipal & Industrial) and <br />Agricultural Demands and Environmental and Recreational Flow Requirements <br />November 2003 <br /> <br />T bl 3 S <br /> <br />T bl 'th P r ' <br /> <br />D t f th C I d R' B' <br /> <br />a e umma ry a eWI re Immary a a or e o ora 0 Iver asm <br /> Irrigation Water Average Historic Average Historic Estimated Crop <br /> Irrigated Requirement Diversions for Groundwater for Consumptive Use - <br /> Acreage(1) (IWR)(2) Irrigation(3) Irrigation(4) Supply Limited(5) <br />River Basin (acres) (acre-feet) (acre-feet) (acre-feet) (acre-feet) <br />Colorado 266,446 409,890 1,719,475 9,000 356,893 <br /> <br />Data Sources: <br />(1) StateCU model input data sets <br />(2) StateCU simulated values <br />(3) State Engineer's Office (SEa) databasel Hydrobase <br />(4) Estimated from SEa wells database <br />(5) StateCU simulated values <br /> <br />Selected river basins might be subdivided into subregions based upon special <br />administrative considerations or hydrologic topology with the appropriate demand <br />summary per region. This will be evaluated as the project evolves. These values could <br />be summarized from existing CDSS data sets at various levels of resolution. <br /> <br />Unless directed otherwise by the basin advisors and technical committee, existing and <br />year 2030 irrigated acreage will be assumed to remain constant with the latest <br />available estimates of actual irrigated acreage. As such, the existing StateCU data sets <br />are suitable, without modification, for calculating future crop demands for the year <br />2030. In the event that irrigated acreage is expected to change, total diversions will be <br />compared to total irrigation water requirements to calculate unit agricultural-use <br />coefficients. The unit agricultural-use coefficient can then be applied to the expected <br />2030 irrigated lands forecast to predict future agricultural water demands. <br /> <br />Methodology for Basins with Existing CDSS Data Sets <br />CDSS datasets have been developed for the Colorado, Gunnison, YampafWhitef <br />Green, San JuanjDolores, and Rio Grande River Basins. Irrigated acreage and crop <br />types have been tabulated for all explicitly represented diversion structures and <br />aggregated diversion structures. The StateCU model data sets contain all necessary <br />climate data to generate monthly crop irrigation water requirement based upon crop <br />type. Irrigation water requirement values at diversion structures will be summed to <br />arrive at a total annual irrigation water requirement value by basin or region by <br />processing the generated datasets and incorporating existing reports using CDSS <br />tools. <br /> <br />The standard method for calculating irrigation water requirements is based upon the <br />modified Blaney-Criddle procedure. In some basins, locally calibrated coefficients for <br />Blaney-Criddle have been developed and will be used when available in StateCU data <br />sets. StateCU includes features to calculate demands using the Penman-Montieth <br />method, but lack of adequate climate data usually limits its applicability in all but <br />specific regions of the State. <br /> <br />The StateCU model provides the functionality to estimate a supply limited crop <br />consumptive use amount based upon historic diversions and soil moisture carryover. <br /> <br />CONI <br /> <br />8 <br /> <br />S:\TASK 8 & 9 SUPPLY AND DEMAND\SWSI DEMAND METHODOLOGY 11-26-03.DOC <br />