OCR Text |
Show and potassium-and the major anions-carbonate, bicarbonate, sul-fate, chloride and nitrate-constitute the bulk of the dissolved constituents in natural waters and very largely determine the quality. A number of minor constituents including boron, silica, fluoride, hydrogen measured as pH, and iron may also occur and be reported in chemical analyses of w.aters. These constituents usually occur in low concentrations and, with the exception of boron, are usually not of great importance in their relation to the soil or to plants. In this report it is unnecessary to discuss the relative merits or demerits of the several dissolved constituents. There is considerable body of good literature on the subject which may be consulted if desired. Many of the effects of the dissolved constituents upon plants and soils are complicated and interrelated and often the effects of several constituents are additive. It is probably sufficient to say here that the three criteria by which the quality of an irrigation water is usually judged are (1) the total dissolved solids concentration, (2) the percentage ratio which the sodium ion bears to the total positive ions, both quantities being expressed in mili-equivalents, and, (3) in areas where it occurs in sufficient concentration to be important, the boron concentration. In the last few years the sodium adsorption ratio has been advanced by workers as being more reliable than the sodium percentage as an indicator of the effect of relative cation concentration on sodium accumulation in the soil. For the purposes of this report, however, the earlier criteria will be used. Permissible limits to define the quality of waters for irrigation use have been proposed by various workers and in general the values are in good agreement. A diagram or chart has been prepared by L. V. Wilcox and others of the Rubidoux Laboratory of the Department of Agriculture,* which sets forth graphically the suitability of irrigation waters based upon the first two criteria. (See Figure II) The occurrence of boron in toxic concentrations in some irrigation waters makes it necessary to consider this element in grading water quality. C. S. Scofield** has proposed limits for boron that have proved satisfactory and are recommended. Investigation shows that boron concentrations in the waters of the Colorado River are too low to be significant and the details of its occurrence have not been included in the report in the quality of water tabulations. The available data, however, show that boron concentrations at Lees Ferry, even under full development of the Upper Basin, will lie within that range classified as "good" waters even for boron-sensitive crops. Chemical Composition of Colorado River Waters A continuous program of quality of water sampling of the Colorado River was initiated by the U. S. Geological Survey start- * "The Quality of Water for Irrigation Use" by L. V. Wilcox, Tech. Bulletin No. 962 USDA. ** "The Quality of Water for Irrigation Use," p. 27. -29- |
Source |
Original book: [State of Arizona, complainant v. State of California, Palo Verde Irrigation District, Coachella Valley County Water District, Metropolitan Water District of Southern California, City of Los Angeles, California, City of San Diego, California, and County of San Diego, California, defendants, United States of America, State of Nevada, State of New Mexico, State of Utah, interveners] : |