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<br />7
<br />
<br />Table 5.- Annual discharge, Rio Grande at Rio Grande City, Tex., 1901-64
<br />
<br /> Rio Running Rio Running Rio Running
<br /> Grande average Grande average Grande average
<br />Year at (acre-feet) Year at (acre-feet) Year at ( acre-feet)
<br /> RG City RG City RGCity
<br /> (Ac.-ft.) 5-yeal ~O-year (Ac.-ft.) 5-yr 10-yr (Ac.-ft.) 5-yr 10-yr
<br />1901 3,370 - - eL923 5,000 6,451 5,591 1945 3,190 5,240 4,727
<br />2 3,773 - - 24 4,667 5,384 5,198 46 3,481 4,398 4,565
<br />3 4,755 - - 25 7,035 5,203 5,451 47 2,714 3,551 4,572
<br />4 7,377 - - 26 4,856 5,604 5,567 48 3,744 3,738 4,333
<br />5 8,562 5,568 - 27 4,248 5,162 5,622 49 4,342 3,495 4,449
<br />6 8,529 6,600 - 28 4,326 5,027 5,738 50 2,228 3,302 4,271
<br />7 5,760 6,997 - 29 3,112 4,716 5,049 51 1,921 2,990 3,694
<br />8 4,423 6,931 - 30 4,855 4,280 4,741 52 1,007 2,649 3,100
<br />9 7,612 6,978 - 31 3,868 4,082 4,843 53 1,828 2,266 3,001
<br />10 3,977 6,061 5,814 32 9,134 5,060 5,110 54 2,161 1,829 2,662
<br />11 4,280 5,211 5,905 33 7,823 5,759 5,392 55 2,817 1,947 2,624
<br />12 4,499 4,959 5,977 34 3,010 5,739 5,227 56 1,906 1,944 2,467
<br />13 4,523 4,979 5,954 35 6,744 6,160 5,198 57 1,638 2,071 2,359
<br />14 8,600 5,176 6,077 36 5,104 6,364 5,222 58 6,620 3,029 2,647
<br />15 4,500 5,281 5,670 37 2,643 5,065 5,062 59 2,691 3,135 2,482
<br />16 3,700 5,165 5,187 38 6,135 4,728 5,243 60 2,205 3,013 2,479
<br />17 3,700 5,005 4,981 39 3,188 4,763 5,250 61 2,350 3,101 2,522
<br />18 3,160 4,733 4,855 40 4,008 4,216 5,166 62 2,238 3,221 2,645
<br />19 10,000 5,013 5,094 41 7,691 4,734 5,548 63 1,751 2,247 2,638
<br />20 7,940 5,701 5,490 42 6,947 5,594 5,329 64 1.640 2,037 2.586
<br />21 2,850 5,431 5,347 43 2,809 4,929 4,828 lAve. 4,340 - -
<br />22 6,460 6,083 5,543 44 5,559 5,434 5,083
<br />
<br />The graphs of figure 3 show that the amount of water in the river was not
<br />
<br />much diminished with time prior to 1944, the average flow being about 5,340,000
<br />
<br />acre-feet per year. From 1944 to 1956 the flow decreased from 5,200,000 to
<br />
<br />2,600,000 acre-feet per year, and has remained at the latter figure since 1956.
<br />
<br />This decline in flow indicates that the average of the entire historical record
<br />
<br />may not be an accurate measure of water that is available now or will be available
<br />
<br />in the future. The indicated decline in flow from 1944 to 1956 may have been
<br />
<br />caused by construction of irrigation projects that consume considerable amounts
<br />
<br />of water, by the unusually severe drought of the 1950's, or by a combination of
<br />
<br />both of these influences. The latter probably is the better assumption; if correct,
<br />
<br />this means that the average flow in the future will be greater than the flow for
<br />
<br />the past eight years (2,640,000 acre-feet per year) but will not be as great as
<br />
<br />the 1901-64 average (4,340,000 acre-feet).
<br />
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