Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: August 25, 2011
Publication Date: N/A
Interpretive Summary: In arid and semiarid rangelands, sources of drinking water for livestock must be developed and forage for grazing also needs to be enhanced. Typically, the simplest approaches are the most effective and also the least costly. These approaches are ones that have been traditionally used for thousands of years. For livestock drinking water, stock ponds using small earthen dams are the primary storage structure supplemented by several deep wells and herd management based on rainfall forage monitoring. For forage enhancement, shallow water ponding dikes are used to slow down overland flow and pond water which are used to slow down overland flow and pond water which leads to infiltration, increased soil moisture, and vegetation growth. Both the stock ponds and the water ponding dikes have been successfully developed at the Jornada Experimental Range. Techniques to accomplish this are documented in scientific literature and are cost effective for most arid and semiarid rangelands. The users of this information will be employees of NRCS and BLM as well as technicians for state agencies and universities.
Technical Abstract: Water harvesting is a methodology that has been used for over 9 millennia to concentrate, collect, and distribute water that normally would be inaccessible for applications in irrigated agriculture, individual domestic water supply, and rangeland management. Although used widely for agriculture and domestic supplies, water harvesting is a management technique seldom used for rangeland applications despite numerous positive results. It is possible that the technique may be overlooked for a variety of possible reasons, the least compelling being that it is an ancient method based on archaic technologies. As more and more stresses are placed on our natural resources through effects of a growing population, increased pressure on existing groundwater supplies, and climate change, a renewed use of water harvesting would have positive outcomes. The simplest technique is to use water ponding dikes which slow down surface runoff, allow infiltration and increase soil moisture, and promote significant vegetation growth for habitat cover and forage. It is recommended to use water ponding dikes because of the direct response: shallow water ponds form after high intensity rainstorms, infiltration and soil moisture increase, and growth of native vegetation (sometimes delayed for years because of the type and distribution of rainfall experienced across an area) is enhanced. The advantages of water ponding dikes are that they are simple to install, cost effective, and make use of water that would be lost to evaporation. The use of water ponding dikes also mimics nature in the way that banded vegetation is arranged on the landscape: bare soil producing surface runoff after a storm, vegetation bands downslope slowing down and catching the surface runoff and increasing soil moisture, and causing increased vegetation growth as if it was located in an area with a higher rainfall. Future experiments are needed on larger areas to determine if these rangeland treatments cause improved vegetation cover that can expand to (or at least be stable over) even larger spatial extents. If water can be supplied effectively to the soil and vegetation complex, such as through water harvesting, it is likely that rangeland restoration projects will have an increased likelihood of success. The use of stock tanks as water sources on rangeland for cattle grazing is a traditional method that has one of the least expensive construction costs amongst a variety of possible methods. In arid regions, it places reliance on trapping surface runoff that will otherwise be lost back into the atmosphere through evaporation. By confining this surface runoff in a pond with small surface area, and water depth of up to 2m, evaporation and infiltration losses are both reduced over what would normally occur if the water was spread out and infiltrated into a stream bed. The groundwater reservoir is not depleted until necessary, e.g., when severe drought years are encountered, and then well pumping would only be relied upon when the pond becomes dry.