Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2001
Publication Date: N/A
Interpretive Summary: Global climate change is happening now. Historical weather records over this last century show that precipitation is increasing both in terms of the number of days we have rain and the intensities of rain. Statistical analyses of the records have indicated that there is a less than one in thousand chance that the changes in these patterns of precipitation could have occurred under a stable climate. We also have good scientific reason to believe that the changes will continue into the next century as well. Although overall the country has become wetter, some areas have been drier, and these trends are expected to continue. As rainfall changes, so does erosion. In this study we used computer simulation models to look at how changes in precipitation might affect erosion rates in the United States. Our results indicate that for every 10% change in total rainfall we can expect a 20% change in surface water runoff and an approximate 17% change in soil erosion. Changes in runoff can have major impacts on flooding, which has been a serious problem in recent years in many parts of the U.S. Changes in soil erosion may mean that we will need changes in our conservation strategies. The impact of this research will be better and more targeted conservation strategies for the future, which will ultimately result in a better soil resource base for growing food in this country.
Technical Abstract: Changes in precipitation have occurred over the past century, and are expected to change more over the next century. These changes will have significant implications for runoff, soil erosion, and conservation planning as areas change differently. This study was undertaken to investigate how runoff and erosion by water can be expected to change as a function of changes in the average number of days of precipitation per year and changes in the amount and intensity of the rain that falls on a given day. The Water Erosion Prediction Project (WEPP) model was used to simulate erosion for three locations, three soils, three slopes, and four crops. Average annual precipitation was changed +/-10% and +/-20% by changing either a) the number of wet days per year, b) the amount and intensity of precipitation per day, or c) a combination of the two. Results indicated that, on average, each 1% change in average annual precipitation induced a 1.28%, 2.50%, and 1.97% change in runoff and a 0.85%, 2.38%, and 1.66% change in soil loss for the three types of precipitation changes, respectively. Comparisons of the results of the soil loss simulations to published relationships for RUSLE R-factors in the United States suggest that the third option of changing both the number of wet days per year and the amount and intensity of precipitation per day is the more realistic scenario for representing changes in precipitation.