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<br />001%8 <br /> <br />Diversions (Imports and Exports) = <br /> <br />~ I=Mlmlnrr of DmmolU . . <br />L.. '-I + - DiversionPercentage * DiverSlOnFlow(l) <br /> <br />Imports are subtracted and exports are added. Diversion Percentage is portion <br />of diversion flow which imports or exports. <br /> <br />Extension of Natural Flows for 1929 to 1970 <br /> <br />As was previously mentioned, the 1970 to 1993 monthly natural flows for stations along the San Juan <br />River and its tributaries above the Bluff gauge were furnished by the USBR. The remaining 1929 to <br />1969 monthly flows for the upper San Juan River and its tributaries were estimated by Keller-Bliesner <br />Engineering using a spatial disaggregation method. A detailed description of the method used in the <br />record extension is contained in the following Section. <br /> <br />For the stations in the lower San Juan River, the 1929 to 1969 flows were estimated using the <br />monthly natural flows for San Juan at Archuleta and San Juan at Bluff from the Colorado River <br />Simulation System (CRSS). The 1929 to 1969 monthly flows for the intermediate stations of <br />Farmington, Shiprock and Four Comers were estimated by calculating them as a fraction of the net <br />CRSS flow between Archuleta and Bluff. This estimation technique is discussed in detail in the <br />following Section. This process pointed out some errors in the CRSS data and this is discussed in the <br />CRSS Data Correction Section. <br /> <br />The San Juan River Model requires flows expressed as monthly gain/loss data sets calculated from the <br />natural flow estimate. As part of the natural flow extension, the gain/loss data are calculated between <br />river reaches. These data sets will be referred to as gain/loss files and are configured as separate <br />objects in the Model in the appropriate reaches. <br /> <br />Tributary Gaaes and Gaaes Above Navaio Reservoir <br /> <br />The 1929 to 1969 extensions were done in monthly time steps using a combination of spatial and <br />emporal disaggregation methods. In spatial disaggregation a mass balance across many stations with <br />!mown flows is used to estimate unknown flows at another station within the basin. In temporal <br />disaggregation, typically two stations are involved. One station must have a period of record <br />corresponding to the unknown period of record from the other station. The statistics from the <br />concurrent period of record are then used to estimate the unknown period of record. <br /> <br />The statistical relationships among the stations were developed from the USBR 1970-1993 natural <br />flows and the unknown flows were extended back in time using the relationships and long-term flow <br />records at key stations. Key stations were selected for disaggregating a group of stations in the <br />following manner. <br /> <br />1. The recorded flows were used from several upper basin stations that have near natural <br />flows, meaning there are few diversions above the gauges. The monthly flows for the <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18, 1999 <br /> <br />29 <br />