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<br />001373 <br /> <br />Operation Plan for the Proposed Long Hollow Reservoir-Preliminary Draft, March 17,2004 <br /> <br />these facts, this LHR operation plan will reserve the first 300 AF of active storage in LHR each <br />year for Compact obligations under split river conditions. <br /> <br />4.0 LA PLATA RIVER HYDROLOGIC MODEL <br /> <br />4.1 Model Description <br /> <br />WWE used a water allocation model (MODSIM), developed by Dr. John Labadie, Colorado <br />State University, to simulate flow in and diversions from the La Plata River under pre- and post- <br />LHR conditions. The modeled period included the 14 water years from WY 1989 through WY <br />2002. This study period was selected because of the availability of the flow data from five ) <br />stream gauges, which included the Long Hollow gauge after it was installed in 1988. <br /> <br />Based on 85 years of record at the Hesperus gauge, the study period was about 5 percent drier <br />than average (see Table 2). The average discharge for the 14-year study period was 27,577 AF, <br />which ranks at about the 45 percentile as ranked from dry to wet. Flow data from these five <br />stream gauges and diversion records for 18 irrigation ditches, shown in Figure 7 and included in <br />the back pocket of this report, were used to create the model and develop a water balance for the <br />La Plata River and its tributaries. After calibrating the model using actual data, the model was <br />used to simulate stream conditions in Colorado during the study period with and without the <br />proposed LHR. <br /> <br />4.2 Modeled Scenarios <br /> <br />Two scenarios were modeled. In Scenario 1, water was supplied to New Mexico in an amount <br />equivalent to the historic administrative call from New Mexico during the study period. In <br />Scenario 2, water was supplied to New Mexico in an amount equal to one-half of the now at the <br />Hesperus Gauge between February 15th and December I st of each year (up to 100 cubic feet per <br />second (cfs)). Scenario 2 represents the maximum call that New Mexico may place under the <br />Compact. The ability for LHR to fill in priority was modeled for each scenario. For the study <br /> <br />991-077 .000 <br />March 2004 <br /> <br />Wright Water Engineers, Inc. <br /> <br />Page 4 <br />