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<br />00197Q <br /> <br />natural flow estimates. The fractional distribution was calculated as the mean fractional <br />part for each reach during 1970-1993. During this period the mean annual gain between <br />Archuleta and Bluff was 9881 ac-ftlyr, The fractions were computed as follows: <br /> <br />Archuleta-Farmington. This reach showed a small loss, so the fractional part was <br />assigned as 0.??oo. <br /> <br />Farmington-Shiprock. This reach showed a mean annual gain of 697 ac-ftlyr or a <br />fractional gain of 0.0705 (697/9881). <br /> <br />Shiprock-Four Comers. This reach showed a mean annual gain of 5799 ac-ftlyr or a <br />fractional gain of 0.5869 (5799/9881). <br /> <br />Four Comers-Bluff. This reach showed a mean annual gain of 3385 ac-ftlyr or a <br />fractional gain of 0.3426 (3385/9881), <br /> <br />These ratios show that on average there was no gain or loss in the Archuleta to <br />Farmington reach, while the majority of the gain or loss occurs in the Shiprock to Four <br />Comers reach. <br /> <br />3. Apply reach ratios to CRSS monthly natural now balance. It was assumed that these <br />ratios calculated in step 2 were a reasonable estimate of the distribution of the gain and <br />losses by reach for the 1929 to 1969 period. The ratios were applied to the monthly <br />natural flow balance (calculated in step 1) to partition each monthly value into individual <br />reach components. The natural flow estimate at the gages is back calculated from the <br />natural flow balance. Combining the two sets of data produces a monthly estimate of the <br />monthly natural flow balance for each of the four reaches for the entire period of record <br />(1929-1993). <br /> <br />CRSS Data Correction <br /> <br />Investigation of the gain/loss balances for CRSS Archuleta and CRSS Bluff during 1929-1969 showed <br />some monthly flows in 1957 that appeared inconsistent with upstream flows measured for the San <br />Juan River at pagosa Springs. Disaggregation results of Archuleta natural flows using Pagosa Springs <br />flows showed the CRSS flows at Archuleta were much too small during May and June, 1957. The <br />CRSS flows were approximately 58,000 and 110,000 ac-ft at Archuleta during these months <br />respectively. The CRSS flows at Archuleta were adjusted by adding 50,000 and 100,000 ac-ft for <br />May and June, 1957. Similarly, to maintain a balance at Bluff, monthly flows were adjusted by <br />adding 60,000 and 120,000 ac-ft respectively for May and June, 1957. These adjusted flows were <br />included in the CRSS Archuleta and Bluff key station files. <br /> <br />DRAFT - SJRIP Hydrology Model Documentation <br />June 18, 1999 <br /> <br />31 <br />