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<br />I From- Ror Bllesner To: Shirley Mondy <br /> <br />o <br />,-., <br />~- <br />~>.) <br /> <br />-...l <br /> <br />Date: 01/11/02 Time: 2:56:42 PM <br /> <br />P4!ge2of7 <br /> <br />San Juan River Basin Hydrology Model <br />Key Model Input <br />Draft Plan of Approach <br /> <br />Background <br /> <br />The San Juan River Basin Recovery Implementation Program (SJRlP) Hydrology <br />Committee has approved the revision of the San Juan River Basin Hydrology Model <br />(model) to provide more precise modeling of river flows below Navajo Dam. Three tasks <br />have been contracted to KelIer-Bliesner Engineering: (I) Recommend methodology for <br />and determine inciden1allosses in the basin utilizing eKisling data, (2) Recommend <br />methodology for and determine off.stream depletions, and (3) Reconunend methodology <br />. for and develop software and/or algorithms to disaggregate monthly demands, return <br />flows, tributary flows, gains and losses into pseudo-daily values for use in the daily <br />Navajo dam operational model. This document presents the draft plan of approach for <br />these three methodologies. <br /> <br />The methodologies outlined here rely on the following assumptions: <br /> <br />I. Monthly natural flows will be computed utili7ing consistent assumptions from <br />1929 to 2000 (assuming data are available through 2000) and the same <br />assumptions will be used for model operation as for natural flow calculation. This <br />consistency is essential for accurate modeling and to make the model and natural <br />flows defensible. <br />2. The general model configuration is tile same for model runs as for natural flow <br />computation except that depletions wilI be adjusted to match conditions modeled <br />(e. g. baseline, future development, etc.). <br />3. Daily tirnestep data will be required only for those activities that influence flow <br />downstream of Navajo Dam. including operation of ALP. <br />4. Natural flows are computed at all the gage sites required for model calibration and <br />operation (no spatial disaggregation required). <br /> <br />Incidental Losses <br /> <br />Incidental losses associated with water supply projects are those that are not directly <br />accounted for in primary project demand. Tbey occur as a result of conveyance, <br />application and return flow system losses. For purposes of computation they are <br />considered the consumed portion of these losses. The impact on diversion as a result of <br />the incidentaIlosses will be computed utilizing the calculated efficiency of the project <br />being modeled. It is further propos~d that sprinkler evaporation, while computed <br />separately, be handled in the same manner as incidental losses. Utilizing model <br /> <br />KelIer-Bliesner Engineering <br />Draft San Juan Model Input Data Generation <br /> <br />January 11, 2002 <br />Page 1 <br />