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<br />0019'73 <br /> <br />occur in each reach each month. The natural reach losses are due to phreatophyte consumptive use. <br />The phreatophyte consumptive use was estimated by subtracting the effective precipitation (SCS <br />method) from potential evapotranspiration estimated by the Hargreaves-Samani method. Due to its <br />long record length, the weather station at Bloomfield, NM was used for climate data. The <br />consumptive use, calculated as 1.6 times irrigated pasture's use, was mulitplied by the phreatic area <br />determined from areal photography between river miles 52 and 225. By adding an estimate of the <br />monthly phreatophyte consumptive use to the monthly natural flow balance, we obtain an estimate of <br />the natural ungaged inflow (gain) to each reach. The off-stream depletions within the reach are limited <br />to this amount of ungaged gain. <br /> <br />Using the Shiprock to Four Comers reach as an example, the monthly off-stream depletion adjustment <br />for 1970 to 1993 was done as follows: <br /> <br />Ir (MNFBs,FC + PHREATs,FC) > Off-stream Depletions,Fc <br /> <br />Then New MNFBs,FC = MNFBs_FC - Off-stream Depletions_Fc <br /> <br />Else New MNFBs,FC = PHREATs_Fc (loss) <br /> <br />MNFBs,FC = Shiprock to Four Comers monthly natural flow balance. <br />PHREATs,FC = Shiprock to Four Comers phreatic use in as a loss. <br />New MNFBs,FC = Adjusted Shiprock to Four Comers gain/loss. <br /> <br />This limits the off-stream depletion to no more than the natural gain (MNFB+PHREAT) in each <br />reach. <br /> <br />Prior to 1970 the off-stream depletion adjustment was made by calculating the gains and losses with <br />one monthly natural flow balance for the reach between Archuleta and Bluff. The reach ratios <br />discussed previously were used to partition the gains and losses by reach. For any month this was <br />done as follows: <br /> <br />If (MNFBAR_BF + PHREATA1!.,BF) > Off-stream DepletioIlAR,BP <br /> <br />Then New MNFBAR_BF = MNFBAR_BF - Off-stream DepletioIlAR,BF <br /> <br />Else New MNFBAR,BF = PHREATAR,aF (loss) <br /> <br />MNFBAR,BF = Archuleta to Bluff monthly natural flow balance. <br />PHREATAR_aF = Archuleta to Bluff phreatic use in as a loss. <br />New MNFBAR,BF = Adjusted Archuleta to Bluff gain/loss. <br /> <br />The gains and losses by month for any reach are calculated as: <br /> <br />Gw,1'M = GLA1!._BF * 0.??oo <br />GLFM,s = GW,aF * 0.0700 <br />GLs,FC = GW,aF * 0.5899 <br />GL<c,aF = GW,BF * 0.3401 <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18, 1999 <br /> <br />40 <br />