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<br />0019"/6 <br /> <br />Natural Flow Balance Adjustments <br /> <br />General <br /> <br />In the Daily Natural Flow Balance section of this document it was stated that once calculated, the <br />natural flow balance was static and did not change with development scenario. This is true for both <br />the monthly and daily natural flow balance. However, it was also mentioned that these balances <br />would be adjusted to account for off-stream depletions and lagged return flows. <br /> <br />The San Juan Model as implemented in RiverWare meets demands by diverting water from specific <br />water sources such as rivers and reservoirs. Therefore, the modeled water supply should be natural <br />flow less any off-stream depletions. The water supply used in the model comes from the natural flow <br />estimates, which included off-stream depletions in its calculation. This section describes the methods <br />used to take the off-stream depletions out of the water supply and then integrate them back into the <br />model. <br /> <br />Off-stream Depletions Adiustments to Natural Flow Balances <br /> <br />The San Juan Model was originally configured such that certain depletions that occur in the basin <br />were taken directly from the San Juan. If satisfying this demand would cause the flow in the river to <br />drop below the instream flow requirement, the Model would release water out of Navajo to satisfy the <br />instream flow. In this situation, off-stream demands are effectively being satisfied by drawing on <br />Navajo Reservoir. We have identified certain demands in the basin that we consider off-stream <br />depletions. Filling of a stock pond with runoff water in one of the tributary basin is a typical <br />example. It is impossible for the stock pond to get water directly from the San Juan, but it is a <br />depletion to the basin in that it reduces the inflow to the San Juan River. The following Baseline line <br />items have been identified as off-stream depletions: <br /> <br />1400 ac-ft D Scattered Rural Domestic Uses <br />2200 ac-ft - Stock ponds and Livestock <br />1400 ac-ft - Fish and Wildlife <br />1500 ac-ft - Unspecified Minor Depletions <br /> <br />These items total to 6,500 ac-ft. The natural flow balances or gain/loss files have been adjusted to <br />account for 6,500 ac-ft of depletion. This is done by subtracting the appropriate depletion from the <br />various reach natural flow balances. This necessitates taking a corresponding volume of water out of <br />objects demanding off-stream depletions in the Model. This was done as follows: <br /> <br />I. 1,908 ac-ft subtracted from MiscCarracasToNavajo:NonIRDep. Mapped as 100 ac-ft for <br />Fish & Wildlife, 1,500 ac-ft for Minor Depletions, 308 ac-ft for Stockponds from Subunit <br />1. <br /> <br />2. 1,310 ac-ft subtracted from LaPlataStatelineToFarmington:NonIRDep. Mapped as 1,235 <br />ac-ft for Fish & Wildlife, 75 ac-ft for Stockponds from Subunit 4. <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18, 1999 <br /> <br />37 <br />