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<br />CONI <br /> <br />Methodologies for Estimating and Projecting Urban (Municipal & Industrial) and <br />Agricultural Demands and Environmental and Recreational Flow Requirements <br />November 2003 <br /> <br />This analysis is performed by diversion structure and will be summed to arrive at a <br />total annual crop consumptive use value by basin or region. <br /> <br />Methodology for Basins without Existing CDSS Data Sets <br />A StateCU statewide climate station data set is being developed as part of the CDSS <br />project and may be completed in early 2004. This dataset will provide the means to <br />calculate unit crop irrigation water requirements at selected climatic stations <br />throughout the state. In other words, at climate station A, for 1 acre of crop B, the <br />irrigation water requirement is N. These "unit crop use coefficients," once established, <br />can be multiplied by the irrigated acreage from surrounding service areas to calculate <br />the crop irrigation water requirements. Therefore, the main effort for these basins <br />would be estimating the irrigated acreage and crop distributions. <br /> <br />If the statewide climate station data set is not available in time for SWSI requirements, <br />then the Blaney-Criddle procedure for estimating crop irrigation water requirements <br />in non-CDSS basins cannot be applied. Therefore a different approach will have to be <br />used for estimating irrigation water requirements. Historic diversions and <br />groundwater pumping estimates will be used to estimate the historic water <br />application using average system efficiencies. The application amounts per unit area <br />can be compared to the developed unit crop coefficients from the CDSS basins to <br />arrive at estimates for expected irrigation water requirements and consumptive use <br />amounts. <br /> <br />South Platte and North Platte Basins <br />The State is currently developing the South Platte Decision Support System (SPDSS), <br />including portions of the North Platte Basin. The SPDSS GIS component should have <br />preliminary results delineating lands under irrigation by December 2003. <br />Identification of crop type is not scheduled to be complete until December 2004. If <br />available in sufficient time, the irrigated lands data will be reviewed for accuracy and <br />completeness, and if considered acceptable, this data could be used as the estimate for <br />total acreage being irrigated. Estimates for crop type will be based upon existing <br />studies and reports such as Colorado Agricultural Statistics. For example, <br />Agricultural Statistics will be used to prorate SPDSS irrigated acreage by crop. <br /> <br />Depending upon the availability of SPDSS data, it may be difficult in a <br />reconnaissance-level study like SWSI to determine basin-wide estimates for crop <br />water requirements at other than a coarse level. Therefore, rather than focusing on <br />irrigation water requirements estimated from crops and acreage, it may be more <br />appropriate to review historical diversion records from HydroBase and use existing <br />State reports to estimate agricultural water demands. A more detailed study can be <br />done in the future after the SPDSS effort implements basin models. <br /> <br />9 <br /> <br />S:\TASK 8 & 9 SUPPLY AND DEMAND\SWSI DEMAND METHODOLOGY 11-26-03.DOC <br />