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<br />;]u1997 <br /> <br />Prevention of Negative Model Flows on the Animas and LaPlata <br /> <br />During a few months in some model runs the estimated flow for the La Plata and Animas Rivers is <br />negative. This acts as a depletion forcing water to be released from Navajo to satisfy the apparent <br />demand. This obviously does not happen in reality. It is caused by errors in mapping depletions and <br />return flows. The lack of properly lagged return flows may also contibute to the problem. It has not <br />been fixed in the Model because it is difficult to ascertain which depletions and return flows are <br />correct and which are not. To eliminate the effect of the negative flows on the San Juan, the negative <br />flows are simply filtered out during the model run, This is done by setting the outflow slot for both <br />the La Plata and the Animas confluence slots to a minimum flow of O. The Model will not allow <br />these object to be less than zero. The two slots affected are: <br /> <br />LaPlataAtConfluence:Outflow <br />AnimasAtFarmington:Outflow. <br /> <br />Shortage Sharing Rules <br /> <br />Brad Vickers of Wave Engineering (subcontractor to Keller-Bliesner Engineering) modified the San <br />Juan Model to incorporate simplified shortage sharing rules. The details are explained in the <br />following paragraph. Please note that shortage sharing rules may be turned on or off at will and this <br />feature has not been used in any presented model runs. Due to RiverWare limitations the shortage <br />sharing rules are overly simplified to be of much use. This is a source of model improvement in the <br />future. <br /> <br />As currently implemented in the Model, under a shortage sharing situation NIIP, Hammond, San Juan <br />Power Plant, ALP, San Juan Chama and instream flows will be shorted by a percentage of their <br />individual depletions. The shortage share rule works as follows. In March, the forecasted July <br />Navajo Reservoir storage is compared to a user entered data table. This data table consists of Navajo <br />storage and corresponding percent shortage values. If the estimated Navajo storage is within the <br />bounds of the table, the corresponding shortage percentage is used. The projects and instream flows <br />are shorted the given percentage and remain shorted the same percentage though the end of the <br />calendar year. If the forecasted NavajO Reservoir storage is not within the bounds of the table. <br />nothing is shorted. <br /> <br />Reservoir Stage-Area-Capacity Tables <br /> <br />The Stage-Area-Capacity tables for Navajo Reservoir have been updated. These were received from <br />Dave King in September 1998 and were incorporated in the model. The maximum OLive CapacityO <br />is 1,701,300 ac-ft. <br /> <br />Minimum Navajo Reservoir Elevation <br /> <br />A new table slot called MinElevation was added to the ReservoirData data Object. This slot holds <br />monthly minimum reservoir pool elevations for each of the 6 reservoirs in the model. This feature <br />was incorporated to allow a variable minimum reservoir pool elevation by month. The established <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18, 1999 <br /> <br />58 <br />