Universal Soil Loss Equation (USLE) model and GIS were used to evaluate soil erosion in Longdun Reservoir watershed of Nanjing. The results showed that Longdun Reservoir watershed was moderately eroded, and the average soil erosion modulus was 4 343.46 t/km2. More than 63% of the watershed area was at the level of micro or slight erosion. The watershed area with severe erosion was very small, but it contributed to more than 70% of soil erosion amount. Soil erosion in this watershed varied with land use types, and the annual average soil erosion modulus followed the order: upland field > grass > paddy field > forest land, and the soil erosion amount followed the order: upland field > paddy field > grass > forest land. The watershed was divided into 13 sub-watersheds by GIS. The sub-watersheds 4, 5 and 10 were the areas with large soil erosion modulus, and the more attentions need to be paid to the sub-watershed 10 because of its large soil erosion modulus and soil erosion amount. The sub-watersheds 1, 9 and 12 should also be taken care of due to their large soil erosion amounts. Soil erosion amount in all sub-watersheds mainly came from the areas with high erosion grades and severe erosion. Therefore, the more attentions should be paid to the areas with high erosion potentials when the control measures are taken to inhibit soil erosion in future.%本研究以南京市高淳区龙墩水库流域为研究对象，利用通用土壤流失方程(USLE)模型与地理信息系统(GIS)技术结合的方法对流域土壤侵蚀进行模拟预测。结果表明：整个流域年均土壤侵蚀模数为4343.46 t/km2，属中度侵蚀。整个流域微度和轻度侵蚀所占面积比例相对较大，两者所占面积比例之和超过了63%，极强度和剧烈侵蚀虽然所占面积较小，但却产生了超过了70%的侵蚀量。不同土地利用类型中土壤侵蚀强度差异较大，年均侵蚀模数旱田>草地>水田>林地，侵蚀量旱田>水田>草地>林地。通过 GIS将整个流域划分为13个子流域，子流域4、5、10由于区域内大部分是旱田，土壤侵蚀模数较大，为流域内土壤侵蚀的关键源区，子流域10侵蚀模数和侵蚀量都比较大，应该重点关注；而子流域1、9和12由于侵蚀总量较大，也应该保持一定的关注。所有子流域土壤侵蚀量都主要来自高强度侵蚀等级，其中以剧烈侵蚀为主。因此，控制土壤侵蚀应该优先考虑高强度侵蚀等级区域。
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