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( \ .' (~ "--- L 'L.. . (" T: ...... ~.. t~ Al':!ENDIX E rates were corrected for the difference in altitude with a relationship of altitude ani evaporation. The gross reservoir evaporation rate was oorrected for usable precipitation (estimated to be 85 percent of the long- time average monthly precipitation) and also for reduction in consumptive use of river water by lanis UlXler canals in the reservoir area to obtain net reservoir evaporation rates. Evaporation rates were determined on an average monthly basis. Routim Curve - New- Mexico In routing the water i"rom Lobatos through Elephant Butte Reservoir, use was made of the JlRouting Curve-New Mexicoll shown in Figure .B-S. This curve was developld as shown in TableB-9, by determining, from the Otowi now (1929 equivalent), the required Compact delivery in terms of effective inflow to Elephant Butte Reservoir. The tributary inflOlV, Otom to San Marcial, was then added to the Otowi now and the Elephant Butte effective in..f'J.ow waS then deducted from this total now to determine the permissible annual depletion, Otowi to ElephaIrl; Butte Dam. The curve was then plotted, using the Otowi plus tributary inflow between Otowi and ean lIarcial as one ordinate ani the permissible deple- tion as the other ordinate. A trial use of _ this curve indicated that some adjustment; was neceasBr'J to allow for loss of credits in 1929. This loss' materialized during August-September 1929 nooa, through excess deliveries by New- Mexioo to Elephant Butte Reservoir as credit can be taken for m more than 150,000 .acre-feet in a!\V one year. The dashed lim indicates the adjusted curve. Evaporation losses from El Vado. Chamita, and Elephant Butte Reservoirs are reflected in this curve. The curve shOrTS that for an inflow of 540,000 acre-feet, the depletion would be 400,000 acre-feet annually. From an analysis of data in the Middle P.io Grande Project Report dated Aueust 1947 ani from past records, it was concluded that 540,000 acre-feet should be the minimum required now at Otowi. Using this as a base figure, the minimum monthly nows at Otowi and depletions, Otowi to Elephant Butte Dam, were estab- lished as shown in Table E-1O. .' '. ' . ., -. .. '. . . '.' .... ." ." r . .-,'.. I; ~ ','., .,..'-.:: '4"-'" , . E"36 " . . .....