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OfjD~07 '. CIlAP'I'ER V WATER RESOURCES approyed, cover a total of about 126 second-feet of ground water which is far in excess of the indicated recharge, even though many of the rights applied for would be effective only during the irrigation season. Water from the Spanish Valley alluvium is chemically suitable for livestock and for many industrial uses. It varies from suitable to marginal for human drinking. The total dissolved solids vary from about 200 to 800 parts per million. In many places the water of other alluvial aquifers is of poor quality, containing excessive sulfates. Water Quality Surface waters wi thin the study area are generally of sui table chem- ical quality for irrigation, municipal, and industrial uses. The mineral content of the water increases as the water moves downstream because of natural inflow from lower lands and return flows from irrigation. The chemical quality of ground water differs from place to place. In a num- ber of places ground water is being used successfully as a full or sup- plemental supply for irrigation. . Five locations within the study area are known t.o be contributing considerable quantities of dissolved salts to the Colorado River system. Of these the Paradox and Sinbad Valleys are in the Dolores River Drain- age Area, the Onion Creek and Castle Creek Areas drain directly into the Colorado River, and the McElmo Creek Area drains into the San Juan River. Other salt areas exist where water is not present to dissolve the salts and carry them into the river system. Sal t and gypswn beds are exposed in the floor of Paradox Valley near Paradox and Bedrock, Colo. Runoff from the valley percolcttes t.hrough these beds in it.s course toward the Dolores River. Other chemically laden waters reaching the river include ground water, return flows from irri- gated lands in West Paradox Valley, and bank storage entering the river at low flow stages. The chemical content. of ground water, made more con- centrat2d by evapotranspiration by native vegetation, reaches approxi- mately 25,000 parts per million (p.p.m.). Sinbad Valley, near Gateway, Colo., drained toward the Dolores River by Salt Creek, is a] so underlain by soluble Inincrals. During the fall and winter there is no outflow from the valley. During l,he spring and sum- mer, however, Salt Creek contribut.es highly mineralized water into the river. Water samples ranged from 20,100 p.p.m. at a discharge of 110 gal- lons per minute to 49,300 p.p.m. at a discharge of 13 gallons per minute. Onion Creek Spring rises through the gypsum Paradox formation and enters Onion Creek about and anhydrite of the 6 miles above its . 52