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ARS Home » Pacific West Area » Tucson, Arizona » SWRC » Research » Publications at this Location » Publication #102689
Title: DROUGHT AND GRAZING: II. EFFECTS ON WATER YIELD AND QUALITY 1208

Author
item Emmerich, William
item Heitschmidt, Rodney

Submitted to: Journal of Range Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/24/2000
Publication Date: 5/1/2002
Citation: Emmerich, W.E., Heitschmidt, R.K. 2002. Drought and grazing: II. Effects on water yield and quality. Journal of Range Management 55:229-234.

Interpretive Summary: Grazing and drought can interact to change surface runoff, erosion, and nutrient ion transport. Understanding how they interact is essential to good rangeland management. Research was conducted on twelve plots with artificial drought and natural precipitation for one year. A natural drought during the artificial drought prevented direct assessment of the interaction between drought and grazing. The drought produced significant reductions in water and sediment yield, and nutrient ion transport from the research plots. No grazing impact was observed during the artificial drought primarily due to the natural drought. After the drought there was a nonsignificant increase in water and sediment yield, and nutrient transport from the drought treatment plots. The grazing treatments were found to have significantly greater water and sediment yield, and nutrient transport than the ungrazed after the drought. The sediment yield data indicated an additive effect of drought and grazing treatments. The observed significant increases in water and sediment yield, and reduced water quality from the treatments were compared against controls plots. The importance of these observed significant increases is that when they are compared to the natural variability and water quality standards, they were concluded to be minimal.

Technical Abstract: Grazing and drought can have an effect on runoff, erosion, and nutrient ion transport. Understanding the importance of how they interact is essential to good rangeland management. Research was conducted on twelve non- weighing lysimeters half receiving artificial drought for one year and half natural precipitation. Grazing treatments were ungrazed, grazing during drought and not after, and grazing during and after drought. Runoff, sediment yield, and an array of nutrient ions in the runoff water were measured for three years from the lysimeters. During the artificial drought a natural drought occurred, resulting in no runoff from the drought treatment and preventing direct assessment of the interaction between drought and grazing. No grazing impact was observed during the artificial drought primarily due to the natural drought. After the drought the grazing treatments showed significantly greater water and sediment yield, and nutrient transport than the ungrazed. The sediment yield data indicated an additive effect of drought and grazing treatments. The observed significant increases in water and sediment yield, and reduced water quality from the treatments were measured against the controls. When compared to the natural variability and water quality standards, they were concluded to be minimal.