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<br />001975 <br /> <br />4. Complete daily gage flow balances by reach: A daily gage flow balance using the lagged <br />and smoothed data was completed for the Archuleta to Farmington (A-F) reach, <br />Farmington to Shiprock (F-S) reach, Shiprock to Four Corners (S-FC) reach, and Four <br />Corners to Bluff (FC-B) reach. <br /> <br />5. Monthly natural flow balance 1929 to 1969: A monthly natural flow balance between <br />Archuleta and Bluff is segregated into the standard four reaches by the reach ratios <br />developed in the Natural Flow extension (See Appendix 1). A typical equation follows: <br /> <br />(BluffMNF - ArchuletaMNF) * (S-FC reach ratio) = S-FC MNF Balance <br />MNF = Monthly Natural Flow <br /> <br />6. Monthly natural flow balance 1970 to 1993: For the 1970 to 1993 period of record the <br />USBR provided monthly natural flows at each gage location. These were used directly to <br />calculate the monthly natural flow balance and no reach ratios were used as described in <br />step 5 above. <br /> <br />7. Daily natural flow balance 1929 to 1993. The daily disaggregation is performed at the <br />four reaches along the San Juan River; A-F, F-S. S-FC and FC-B. The water moving <br />through these reaches is disaggregated not as daily flows, but as daily gainlloss flow <br />balances. The disaggregation was performed on the monthly natural gainlIoss flow <br />balances using the daily gauged gainlloss flow balances.The daily gauged flow balance at <br />each reach is used as a template to shape the monthly natural flow balance into daily <br />values. Because monthly flow balances can be negative, this procedure differs from <br />multiplying a monthly value by simple daily fractions. It was implemented by taking all <br />daily gauged flow balances for a particular month and shifting the zero line until the sum <br />of the daily set equaled the monthly natural flow balance. Then all daily losses during <br />that month were set equal to a mean daily loss sized to maintain the monthly natural flow <br />balance. The calculation is repeated for every month at every reach. Daily ALP impacts <br />to each reach are added after disaggregation. <br /> <br />The net computational result is that the monthly natural flow balances within each of the four <br />reaches are disaggregated into daily natural flow gainlIoss balances. Any flow corrections to the <br />daily balances are performed after the daily disaggregation. <br /> <br />This process results in the daily natural flow balance for each of the four reaches. The data is a <br />series of positive and negative numbers that are reformatted for input into NFpages.x1s. The natural <br />flow balance is a static data set and does not change as a result of different development scenarios. <br />However, these flow balances are subsequently modified to aocount for lagged return flows, off- <br />stream depletions. <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18, 1999 <br /> <br />36 <br />