Ground water recharge as affected by surface vegetation and management

Abstract

Ground water resources on the high plains of Colorado are being mined for irrigation at a rate surpassing natural recharge of the aquifer. Detailed information on recharge rates, as well as possible methods for increasing recharge, is essential to sound agricultural planning. Various surface soil treatments were investigated in field experiments to determine their effect on ground water recharge. Plots were established in 1967 on initially very dry soil of semi-arid native range land. The water table is about 100 feet below the surface. Water content profiles were measured periodically to determine the downward movement of water resulting from the surface treatments. Changes in the total water content of the profile were used to evaluate soil water accumulation and possible ground water recharge. A 2.5 cm coarse sand and gravel mulch, with vegetation controlled by herbicides, accumulated 50% of the annual precipitation during a two-year period. The sand and gravel mulch with native grass vegetation showed only seasonal fluctuations in the upper 120 cm of the profile with no net accumulation of water. Fallow treatments (chemical and mechanical) did not show significant accumulation until heavy October 1969 snows. Matric potential profiles for various locations on fine textured soils in the high plains area showed high tension values to considerable depths except where conservation practices or irrigation had been used.