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0011f7 -22- V HYDROLOO Y 23. Stream Flow Records - Runoff, There is only one complete long-time reoord of the flow of the Uncompahgre River. Th~t is the record compiled for the flow at Colona (Table 13). The 39 year reoord (1903-41) at that point is the key to the water supply of that area. Other records of varying importanoe, hov.ever, should not be overlooked. Stations were maintained near Fort Crawford at different times from 1895 to 1911; a summer record was made at Hontrose from 1903 to 1923; !Uld reoords were made at Ouray between 1908 and 1924. The more important records whioh will be discussed here are the ones for the Unoompahgre below Ouray, at Delta and at Colona. The reoo~d made below Ouray (not to be oonfused with that at Ouray) is interesting due to the faot that it is oomplete for every month from June 1913 through July 1929, and also because it is just below all important mountain tributaries and above any irrigation Use. The lc,..year reoord when evaluated in terms of the long-time reoord at Colona, indi- oates that the mean runoff fran the mountain area is about 105,000 A.F. per year I or 1,380 A. F. per square mile of the drainage area. In depth of water over the area it amounts to 26 inches. Between the .station below Ouray and the one at Colona there is an increase in measured amounts of about lOO.OOO A.F. If the irri~tion uses above Colona v.ere eliminated this inoroo3e would be more nearly 120.000 A. F. The inorease in drainage area between the two is 36l square miles, so that the runoff is about 332 A.F. per square mile or 6 inches of water in depth over the area. Below Colona the additional drainage area is 749 square miles. The total runoff from this are a amounts to about 40,000 or 50,000 A. F. per year, the greatest portion of whioh comes from the melting snow in the foothill and Plateau regions. The only runoff from the valley area oomes at times of heavy rainfall, whioh evidently is not frequent in an area where the average annual precipitation is only about 9 inohes. The record of the disoharge of the UncompahGre River near its mouth (at Delta) was made, ohiefly for sununer months, from 1903 through September 1931 (Table 14). The station was discontinued from 1931 until June 1938 when it was reestablished for the investigation. It has been maintained oontinuously since that time. The average annual disolmrge of 170,780 A.F. shown on the tabulation is the sum of the avernges of all monthly record", and not the average of the four amual values shown. That figure is pro~ably fairly indioative of the average disoharge at that point sinoe 1903. The reoord of April through October disolmrge