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<br />Texas, for example, projected that average water use per acre would fall <br />from 1.38 acre-feet in 1977 to 0.68 acre-feet in 1990 and 0.65 acre-feet in <br />2020. In much of the Texas High Plains, the Ogallala is relatively thin, but <br />these efficiency improvements were sufficient to keep most irrigated land <br />in production through the Study period. The sensitivity of the results to <br />water use efficiency is shown in the following table, derived from a Texas <br />Alternative Baseline scenario in which projected improvements in water use <br />efficiency were cut approximately in half. <br /> <br />Baseline <br /> <br />Average Land in <br />Year Water Use Irrigation <br />(acre-feet/acre) (million acres) <br /> <br />Baseline Alternative - 50% <br />Less Efficienc <br />Average <br />Water Use <br />(acre-feet/acre) <br /> <br />Land in <br />Irrigation <br />(million acres) <br /> <br />1977 1.38 6.1 1.38 6.1 <br />1990 .68 <br />2000 5.55 1.103 5.52 <br />2020 .65 4.49 1.101 1.19 <br /> <br />In general, the Texas Baseline projected farmers reaching higher levels <br />of water use efficiency than any other state. Because the Aquifer is thin <br />in much of the Texas High Plains the increase in annual withdrawal due to <br />lower water use efficiencies has a magnified effect on land going out of pro- <br />duction which might not be observed during the Study period in areas where <br />the saturated thickness of the Ogallala is thicker, as it is in portions of <br />Kansas and Nebraska. Nevertheless, it is clear that the future of irrigated <br />agriculture is highly sensitive to the rate and extent at which farmers <br />adopt new efficient irrigation techniques. <br /> <br />Agricultural Productivity <br /> <br />Some critics asked if it was reasonable to assume continued increases in <br />crop yields per acre through 2020. Figures 4, 5, 6, 7, and 8 show actual and <br />projected yield increases for key crops in Nebraska. Dryland and irrigated <br />yields are plotted separately. These projections are consistent with those <br />used in all six states. Note that the average annual increase in yield is <br /> <br />A-IS <br />