基于WaTEM/SEDEM模型的沂河流域土壤侵蚀产沙模拟

Modeling soil erosion and sediment yield using WaTEM/SEDEM for Yihe River Basin

基于WaTEM/SEDEM模型,结合临沂水文站和角沂水文站的输沙数据对模型进行校正和验证,分析模拟1975—2015年沂河流域侵蚀产沙的时空变化特征,并进一步研究降水、地形位和土地利用变化对流域侵蚀产沙的影响。结果表明:①沂河流域输沙能力系数Ktc-low和Ktc-high在40 m和150 m组合下效果最优,模型在沂河流域具有较好的适用性。②1975—2015年,沂河流域主要以侵蚀为主,微度侵蚀所占面积最大,其次是剧烈侵蚀,沉积主要分布在河谷处;流域侵蚀强度呈现先增加后减少的趋势,侵蚀模数由1975年的30.92 t·hm^(-2)·a^(-1)增加至1995年的49.32 t·hm^(-2)·a^(-1)再下降至2015年的29.60 t·hm^(-2)·a^(-1);各县(区)平均侵蚀模数为沂水县>费县>沂南县>沂源县>蒙阴县>平邑县>兰山区。③沂河流域土壤侵蚀产沙强度的变化是降水、地形、土地利用等综合作用的结果。1975—2015年,流域降雨侵蚀力呈现先降低后升高又降低的变化趋势,各县(区)平均降雨侵蚀力为费县>兰山区>沂南县>蒙阴县>平邑县>沂水县>沂源县,降雨侵蚀力时空变化与流域侵蚀产沙强度时空变化并不完全一致;地形位等级空间分布与流域侵蚀产沙强度空间分布基本一致,侵蚀产沙的优势地形位区间是4~6级,即高程75~428 m,坡度5°~39°;耕地和林地的转化是土壤侵蚀强度转化最主要的原因,林地转化为耕地使侵蚀强度面积升高3389.97 hm^(2)·a^(-1),耕地转林地则使侵蚀强度面积降低2216.65 hm^(2)·a^(-1),草地与其他土地利用类型的转化对流域侵蚀强度影响较小。该研究可为区域土地利用方式调整和水土流失调控提供参考。

Based on the WaTEM/SEDEM model calibrated and verified by the sediment transport data from Linyi and Jiaoyi hydrological stations,this paper analyzed and simulated the characteristics of spatio-temporal variation of soil erosion and sediment yield in the Yihe River Basin from 1975 to 2015,and further studied the effects of precipitation,terrain and land use changes on soil erosion and sediment yield in the basin.The results showed that:(1)The sediment carrying capacity coefficients Ktc-low and Ktc-high in the basin were optimal under the combined effect of 40 m and 150 m,and the model had good applicability.(2)From 1975 to 2015,the basin was dominated by soil erosion,and the area of micro soil erosion was the largest,followed by severe soil erosion,and soil deposition was mainly distributed in the valley.Soil erosion intensity increased first and then decreased,and the soil erosion modulus increased from 30.92 t·hm^(-2)·a^(-1) in 1975 to 49.32 t·hm^(-2)·a^(-1) in 1995,then decreased to 29.60 t·hm^(-2)·a^(-1) in 2015.The average soil erosion modulus of each county(district)was listed in an order of Yishui county>Feixian county>Yinan county>Yiyuan county>Mengyin county>Pingyi county>Lanshan district.(3)The variation of soil erosion intensity was the result of the comprehensive effects of precipitation,terrain and land use.From 1975 to 2015,the rainfall erosivity of the basin showed a trend of first decreasing,then increasing and decreasing again.The average rainfall erosivity of each county(district)was in an order of Feixian county>Lanshan district>Yinan county>Mengyin county>Pingyi county>Yishui county>Yiyuan county,and the spatio-temporal variation of rainfall erosivity were not completely consistent with that of the soil erosion intensity.The spatial distribution of terrain niche grade basically coincided with that of the soil erosion intensity.The dominant terrain niche range of soil erosion was 4-6 grades,which meant that the elevation was 75-428 m,and the slope gradient was 5°-39°.The transformation between cultivated land and forest land was the main reason for the conversion of soil erosion intensity.The area of erosion intensity increased by 3389.97 hm 2·a^(-1) when forest land was transformed into cultivated land,and decreased by 2216.65 hm^(2)·a^(-1) when farmland was converted to forest land.However,the conversion of grassland and other land use types had less impact on the soil erosion intensity of the basin.This study can provide a reference for regional land use pattern adjustment and soil erosion control.