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<br />Sare 85,000 acres of chico land are on deep to shallCM, nDderately
<br />coarse to coarse textured soils that are suitable for cropping.
<br />under fleading or raN irrigation methods, this land does best if
<br />a sub is maintained at a rather shallCM depth so that irrigation
<br />frequencies can be lengthened and arrounts of water applied each
<br />irrigation can be reduced. It is thought that with the use of
<br />sprinkler irrigation the maintenance of the sub on this land would
<br />bec::ane less inportant. About 92,000 acres of chico land have deep,
<br />medium and nDderately fine textured soils which, if drained, would
<br />be suitable as surface irrigated land. Most of this land is located
<br />along drainage-ways or in natural depressions or areas without out-
<br />fall potentials unless natural drainage-ways or streambeds are
<br />deepened. In total, there are about 218,000 acres of chico land
<br />which could be safely drained and would be suitable for irrigation.
<br />1cM annual precipitation would make dJ:yland fanning inpossible and
<br />ron-irrigated grass production uneconanica1.
<br />
<br />conclusive information on water recovery potentials on greasewood-
<br />rabbitbrush areas is alrrost non-existent. Studies in utah by the
<br />Grological survey 1/ indicate that greasewood cover used about
<br />2-1/2 acre-feet of-water per acre per year where the water table
<br />was two feet belCM the surface of the ground. Bittinger and Enix Y
<br />using the Blaney-Criddle method of determining water use , arrived
<br />at an average water use by native vegetation of about 21 acre-inches
<br />per acre during the grCMing season. T. W. Robinson 3/ (Grological
<br />survey) estimated that in Colorado the evapotranspiration fran
<br />1,709,000 acres of phreatophytes and hydrophytes was 3,210,000
<br />acre-feet annually. Certainly, with a limited precipitation, if
<br />ground water is reduced by drainage, evapotranspiration by plants
<br />would be decreased. The Bureau of Reclamation 4/ has proposed a
<br />closed basin drain, and their studies indicate that lCMering the
<br />water table to under eight feet would generally control or reduce
<br />the chico resulting in recovery of about 40,000 acre-feet per acre
<br />per year fran 127,000 acres of land.
<br />
<br />D. C. Muckel, ARS, 5/ reports an approximate annual water use of two
<br />acre feet for rabbi tb:rush and 1. 5 acre feet per acre for greasewood
<br />at Humboldt River, Nevada. Assuming that an acre of chico uses about
<br />two acre feet of water per year and that about 30 percent of this is
<br />available for salvage with drainage, then about 65,400 acre-feet
<br />of water are available annually for salvage in the chico land of the
<br />San Luis Valley. However, this assumes that the chico would not be
<br />replaced by other water-loving plants with, perhaps, deeper rooting
<br />habits. Also, this asstlltption would preclude irrigated use of the
<br />land drained, which would probably take rrore water than that being
<br />used by the chico. Several thousand acres of chico land have been
<br />cleared and the land irrigated from wells in the last few years.
<br />
<br />1/ See reference 22
<br />2/ See reference 16
<br />3/ See reference 31
<br />4/ See reference 18 20
<br />5/ See reference 26
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