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':'~~~~:'~'.'?;':' , '.Y ,~ ',<' ,:~,\ :,~;:{.L.t.;:,.'2,':'t(::' '~":- ':-'~:~, . ':':~'f!,{l}-::.. ";"'" .,<.-.... "'~':_' c'; , <~':%. -'. ., ,'t,,_, ;';) :-i",:< ';it.:' ,." ,:,,~,;:":. '.~~:t:t{:', ryl[ :'>~>;">J' ,', './";/ ;.,;", ."-/\:~~,; ;~f: ",.", '[~'" >"'r';>.>'. 'c' ..~.,.... ."~",;." ,. ',,' \'::~, 'i .'1' )..(;~.>, '= '0:,:- ,.... .,~ ,C',',_ '-';'- , .",,-. . ~: "'" "'-\ ., :-; .' ~ ,-',;,"}: "",, \ "~ -"'_.0,-';' tion water, An irrigation water having a high sodium peroentage will, after a time, give rise to a soil having a large proportion of t-eplaceable sodium in the colloid. Clay which is partially sodium-saturated is highly dispersible in the absence of flocculating salts and has a tendency to migrate downward through the soil and accumulate at lower levels. As a result the surface of the soil may be relatively coarse in texture and friable. However, below,where the clay accumulates, the soil develops a dense layer of low permeability. A quality analysis, taken in 1952 by the Corps of Engineers, reveals that the amount of exohangeable sodium tends to increase when water is impounded in Jehn Martin Reservoir, and to deorease drastically when the river flows unrestricted through the Reservoir. On May 12, . with storage water in the Reservoir, a sample taken one-half mile below the dam showed 340 parts per million of sodium, or 30 percent of the total cation eXChange capad ty. The Reservoir was emptied on June 1. A sample taken at the same location on June 2 showed 192 ppm of sodium, or 25 per cent of total cation exchange capacity. By July 7 the amount had fallen to 88 ppm, or 8 per Cent of the cation exchange capacity. If irrigation water contains available calcium it is exchanged fer excese sodium in the soil colloid, promotes flOCCulation and increases the friability of a saline soil. The above analysis, however, shows a decrease in calcium content during periods of impounded water and an increase when river flow passes through the Reservoir. The above discussion shows that the quality of the water deteriorates when it is impounded. This factor, plus the increase in transportation loss, the raise in ground water, level, and the reduction of erganic material carried by stilled water, is the basis upon which the relative values of silt-laden and clear waters were determined. Reservoir losses Proponents of the permanent pool mU3t realize that certain 108seE: Occur from clIer;y body of water. In the case of John Martin Reservoir it is ob\Tic!Us from the record that in several past years there has been no irrigd.ion stornge for as long as 6.months at a time. This reoord would indicate that during auch periods all losses attributed to impounded water lmuld of necessity have to be borne by the permanent :pool. Furthermore, these periods occur during tha 7 months from April to October when at least 75 per cent of the total annual loss due to evaporation is felt. The annual less chargeable to evaporation averages 65 vertical inches per year. ThiA would mean a 10A8 of 5,600 acre feet from the 10,000 acre foot pool during the summer months and a loss of nearly 7,500 acre feet for the Year. Seepage lor!l:lee arc not eo large as thOSe from evaporation, but will run at the approximate rate of 5 cubic feet per second (frcm De-vis, Handbook of AoPlied Hvdraulics), This loss will amount to 10 acre feet per day and may reach a maximum of 2,000 acre feet during a period such as discussed above. Durir..g the remainder of the year seepage lossen --.Page 4 -- ",--,? "{. '" \'i~.;. ' .~ ,,' ',.):'<:'" ..,',;' ,-', ^,-S;'~i " :' -; ~::: 1 ':('1 ,-.. .