Evaluation of land-use and land-treatment practices in semi-arid western United States

Abstract

There are about 81000000 hm ² of arid to semi-arid rangeland in the 11 Western States of the United States. Much of this area was subjected to poor land-use practice in the early days of settlement resulting in deterioration of plant cover and severe erosion. Beginning in the 1930s land-treatment programmes were initiated to restore the range and control runoff and erosion. Results of investigations designed to evaluate the effects of land-use and land-treatment programmes are discussed. The types of practices considered are: (1) grazing control, (2) vegetation modification, (3) mechanical land treatments and (4) water spreaders. Grazing control alone reduced runoff by 30 % and sediment yield by 35 % in the Badger Wash basin of western Colorado. Vegetation conversion from shrubs to grass generally does not increase water yield, however, sediment yields are reduced as much as 14 times as shown by a controlled experiment at Boco Mountain in central Colorado. Of the many types of mechanical land treatments designed primarily to increase infiltration, the most effective is contour furrowing. Water spreading on valley floors by diverting flood flows increases forage production, reduces flood peaks and sediment loads to downstream areas. All treatment practices designed to improve plant cover, induce infiltration, or control flood flows will use water. Therefore, these practices must be evaluated with regard to their effect on water yield, which is often critical in semi-arid regions.