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r APl'ENDlXE STRE:l!MFLOW Run-off of the Rio Grande and its tributaries is mainly produced by snow melt. Rain is a contributing factor when it falls during the snow melt season ani, infrequently, as heavy summer ani fall rains. TIle pattern of annual run-off is fairly uniform but the total is ve~ erratic from year to year. ,/~ An annual hydrograph of the Rio Grande near Del Norte, Colorado, is shown in Figure E-3~ The maximum discharge of record at this station' was 18,000 cubic feet j:er second 17hichoccurred on October 5, 1.911. This need was caused by a ve~ heavy rain over the watershed. The minimum dis- charge of record was 77 cubic feet j:er second and occurred on December 29, 1950. The average d.ischarge, 18C~1951, is 951 cubic feet per second. Tile characteristically high flows of late Hay, June, ani early July are the nomal result of the meltiqs of the accumulated winter snows in the higher elevations. Reduction of these flows to eliminate flood damages is desirable. :Regulation of the flows to relieve annual late season irrigation shortages is. also desirable ani enables tlle realillation of the largest benefits to be derived frolll project operation. . Figure E-4 lists tbe principal gaging stations and their periods of record. Locations of the main stations are shown on Figure E-5. Most of these records are published in Water SUpply Papers of the U. S. Geolog- ical Survey. Early publications of these, and records kept by tbe Colorado State Engireer, are not generally available. The pertinent records a."'El tabulated in Tables E-l through E-S. QUALITY OF WilTER The quality of the water in the Rio Granie at Del Norte has been investigated several tiaes by different agencies. The general determina- tion is that. the water is of suitable quality for irrigation purposes. Table E-6 gives an a~lysis. of samples taken near Del Norte in 1936. As shown by Table E-6, the sediment load of the Rio Grande ia ve~ small. This is due to the control afforded by upstream reservoirs, to the excellent forest cover over the headwaters of the Rio Grande, and the tYj:e of run-off. Because of the low sediment inflow, no appreciable capacity for sediment storage would be required in Wagon Wheel Gap Reser- voir. WllTER RIGHt'S APD THE RIO GRAIIDE COllPACT r. A "".... ~~ , . 'j .- ...,,-'""....- ,. , Water RiEZhts The project area comprises tbe greater part of Colorado Water District No. 20 which was established by the State of Colorado and is administered by the Office of the Colorado State Engineer. Approximately 500 appropriations for the use of natural stream flow are listed. These appropriations total about 6,000 cubic feet per second which is in excess of six times the reCQrded average. annual stream flow at Del Norte. E-5 j"