|Le Bissonnais, Y.|
|Van Oost, K.|
Submitted to: Proceedings of the World Water and Resources Congress
Publication Type: Proceedings
Publication Acceptance Date: 2/20/2005
Publication Date: 5/14/2005
Citation: Nearing, M.A., Jetten, V., Baffaut, C., Cerdan, O., Couturier, A., Hernandez, M., Le Bissonnais, Y., Nichols, M.H., Nunes, J.P., Renschler, C.S., Souchere, V., Van Oost, K. 2005. Modeling response of soil erosion and runoff to changes in precipitation and cover. Proc. World Water and Environ. Resources Congress 2005, May 15-19, Ankorage, Alaska. Interpretive Summary: The consensus of atmospheric scientists is that the earth is warming, and as global temperatures increase the hydrologic cycle is becoming more vigorous. The Intergovernmental Panel on Climate Change (IPCC) has reported that there has been a very likely increase (probability 90 to 99%) in precipitation during the 20th century in the mid-to-high latitudes of the Northern Hemisphere. Much of the increase in precipitation that has been observed worldwide has been in the form of heavy precipitation events. For example, Karl and Knight (1998) reported that from 1910 to 1996 total precipitation over the contiguous U.S. increased, and that 53% of the increase came from the upper 10% of precipitation events (the most intense precipitation). Soil erosion rates may be expected to change in response to changes in climate for a variety of reasons, the most direct of which is the change in the erosive power of rainfall. Soil erosion responds both to the total amount of rainfall and to differences in rainfall intensity, however, the dominant effect appears to be rainfall intensity and energy rather than rainfall amount alone. In this study seven soil erosion models were used to evaluate the effects that future changes in rainfall intensities and amounts, as well as plant cover, can be expected to impact soil erosion rates. The results of this study are alarming. If the trends reported for precipitation in the United States and Europe over the last century continue, significant consequences will incur. If rainfall amounts during the erosive times of the year were to increase roughly as they did during the last century in the United States, the increase in rainfall would be on the order of 10%, with greater than 50% of that increase due to increase in storm intensity. If these numbers are correct, and if no changes in land cover occurred, erosion could increase by something on the order of 25 to 55% over the next century. Correspondent values for runoff are 23 to 31%. Both storm water runoff and soil erosion are likely to increase significantly under climate change unless offsetting amelioration measures are taken.
Technical Abstract: Global climate has changed over the past century. Precipitation amounts and intensities are increasing. In this study we investigated the response of seven soil erosion models to a few basic precipitation and vegetation related parameters using common data from one humid and one semi-arid watershed. Perturbations were made to inputs for rainfall intensities and amounts, and to ground surface cover and canopy cover. Principal results were that: soil erosion is likely to be more affected than runoff by changes in rainfall and cover, though both are likely to be significantly impacted; percent erosion and runoff will likely change more for each percent change in rainfall intensity and amount than to each percent change in either canopy or ground cover; changes in rainfall amount associated with changes in storm rainfall intensity will likely have a greater impact on runoff and erosion than simply changes in rainfall amount alone; changes in ground cover have a much greater impact on both runoff and erosion than changes in canopy cover alone. The results do not imply that future changes in rainfall will dominate over changes in land use, since land use changes can often be drastic. Given the types of precipitation changes that have occurred over the last century, and the expectations regarding changes over the next century, the results of this study suggest that there is a significant potential for climate change to increase global soil erosion rates unless offsetting conservation measures are taken.