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<br />. <br /> <br />. <br /> <br />EXHIBIT A <br /> <br />Scope of Work <br />CRDSS Variable Efficiency Evaluation <br />February 28, 2001 <br /> <br />INTRODUCTION <br /> <br />The Colorado Water Conservation Board (CWCB) has requested an investigation into the costs and <br />benefits of simulating the CRDSS (western slope) basin scenarios using the enhanced StateMod water <br />resources planning model. The StateMod enhancements include the modified direct solution algorithm <br />that accounts for variable efficiencies and soil moisture storage. The current CRDSS basin scenario <br />simulations use average monthly efficiencies for each year of the analysis. This methodology is believed <br />to adequately represent efficiencies during average hydrologic years, however, the consumptive use <br />analysis for these basins show that efficiencies can vary significantly in dry and wet hydrologic years. <br /> <br />In addition, the StateMod modifications include a soil moisture reservoir storage routine that allocates <br />excess diverted surface water to the soil reservoir and, during times of surface water shortage, allows <br />demand to be met from the soil reservoir. The soil moisture accounting is believed to more accurately <br />represent actual irrigation practices in arid areas. <br /> <br />The objective of this Scope of Work is to: <br />. Use the Yampa River basin as the "test" basin; prepare the required new or revised input files for the <br />StateMod model. Run the Yampa River basin StateMod scenario using variable efficiency and soil <br />moisture accounting. <br />. Analyze the Yampa scenario results to estimate the benefits of simulating the other CRDSS basin <br />scenarios using the enhanced StateMod in terms of increased accuracy and flexibility in the <br />representation of water use and river flows. <br />. Prepare a step by step procedure memorandum for developing input files; simulating the basin <br />models using the enhanced StateMod; and presenting and comparing the results to previous model <br />results. <br />. Estimate the costs associated with simulating the other CRDSS basin scenarios using the enhanced <br />StateMod based on the procedures determined for the Yampa River basin. <br />. Prepare a recommendation for simulating all of the CRDSS (western slope) basins using the <br />enhanced StateMod based on costs and benefits. <br /> <br />TASK 1- SIMULATE HISTORIC YAMPA STATEMOD MODEL WITH VARIABLE <br />EFFICIENCY AND SOIL MOISTURE ACCOUNTING <br /> <br />Background: <br /> <br />The Yampa River Basin StateMod monthly model is currently being used by the CWCB to run "what-if" <br />scenarios in conjunction with the U.S. Fish and Wildlife Service. In addition, the Yampa River Basin is <br />the "test" basin for determining the cost and benefits of developing daily models for the CRDSS <br />(western slope) basins. Therefore, the Yampa River basin has also been chosen to be the "test" basin for <br />implementation of StateMod with variable efficiencies and soil moisture accounting. <br /> <br />StateMod is a demand driven model. The current CRDSS basin historic data sets use the historic river <br />structure headgate diversions, plus water right priorities, to simulate diversions. When StateMod is <br /> <br />C:\Cdss\statemodWariable eft evaluation contract_ 4.doc <br /> <br />Page 1 0 <br />