OCR Text |
Show PART II DESCRIPTION OF REGION River system per annum. It further establishes the obligation of Colo- rado, New Mexico, Utah, and Wyoming, designated States of the upper divi- sion, not to cause the flow of the river at Lee Ferry to be depleted below an aggregate of 75 million acre-feet for any period of 10 consecu- tive years. The Mexican Water Treaty defines the rights of Mexico to the use of water from the Colorado River system. It guarantees the delivery of 1,500,000 acre-feet of Colorado River water annually from the United States to Mexico. By the Upper Colorado River Basin Compact the use of water appor- tioned to the Upper Basin is divided among the Upper Basin States and principles are established to govern deliveries of water to meet the Lee Ferry flow obligations. By the compact, Arizona is granted the con- sumptive use of 50*000 acre-feet of water a year and the other States are each apportioned a percentage of the remaining consumptive use as fol- lows: Colorado 51*75 percent, New Mexico 11.25 percent, Utah 23 percent, and Wyoming 1^ percent. The quality of surface water generally is very good in the Upper Colorado Region and except in a few areas is satisfactory for irrigation, livestock watering, recreation, and for municipal and industrial purposes. The average concentration of dissolved solids is generally less than 100 mg./l. in streams near the mountains. The weighted average concentration does not exceed 500 mg./l. in most main streams and their principal trib- utaries except in some lower reaches where concentrations occasionally may be as high as 3*000 mg./l. Water in the lower reaches of the main streams is classified as very hard. The quality of ground water varies widely but overall it is not as good as that of the surface water. 18 |