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..... ~ M 'f-/ (;) (:..' the river at Alamosa is about 4,000 cubic feet per second. A Jduction in diversions on the Rio Grande below Del Norte should not .esult in flows at Alamosa in excess of this amount. Analysis of the records indicates that when flows at Del Norte are between 2,500 c.f.s. and 4,000 c.f.s., the corresponding aggregate diversions below that point are between 2,600 c.f.s. and 3,700 c.f.s. If the headgates of all these ditches were to be closed when flows at Del Norte are within this range, the river flow at Alamosa would not generally be excessive. The closure of these ditches for one week would result in the delivery of from 40,000 to 45,000 acre-feet at the state Line over and above the amount which would reach that point under current conditions of water use. This closure could be made when the flow at Del Norte reached 2,500 c.f.s. and it appeared that the rise to peak flows was occurring. If the rise to a peak of 4,000 c.f.s. should occur too rapidly to permit closure for a week, the headgates should be re- opened in order to prevent flooding at Alamosa when Del Norte flows are in excess of 4,000 c.f.s. A subsequent closure could then be made on the recession from the peak for a time sufficient to obtain the required delivery. Inspection of the records discloses that in each of 11 of the 14 years studied there were at least 7 consecutive days, either preceding or following the peak, on which the mean daily dis- charge at Del Norte was between 2,500 c.f.s. and 4,000 c.f.s. The remaining 3 years were those when exceptionally low annual runoff occurred. During years in which index flows are above average, and indications are that the annual deficiency will be considerably greater than average, there generally are comparatively long periods in which Del Norte flows are within the above limits. At such times, diver- sions could be shut down a second time for a few days, in order to compensate for the inability to meet the average deficiency in years of extremely low runoff without unreasonable curtailment of diver- sions. Conejos River. The average annual deficiency in deliveries scheduled for the Conejos and tributaries has been about 23,500 acre- feet between 1950 and 1964. The safe channel capacity in the Conejos below the mouth of the San Antonio is about 1,500 cubic feet per second. The platoro Reservoir, high on the Conejos, has a flood con- trol function to attempt to control runoff at the gaging station at Mogote to a maximum of 2,000 c.f.s. At this point diversions from the Conejos River are generally about 2,000 c.f.s. Peak flows on the San Antonio and Los Pinos usually occur before the peak on the Conejos. Diversions from these tributaries range between 300 c.f.s. and 675 c.f.s. for index flows between 500 c.f.s. and 1,700 c.f.s. Channel capacity on the San Antonio is so restricted that shutting off diver- sions at these times would result in flooding. When discharges at the Mogote gate are between 700 c.f.s. and 1,500 c.f.s., the corres- ponding diversions range between 900 c.f.s. and 1,200 c.f.s. If at Memo -2- April 2, 1965