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通过赵家沟小流域1993年前后坝库泥沙淤积量和~(137)Cs含量的对比,分析了黄土丘陵区梁峁坡地退耕后流域输沙模数和沟谷地、沟间地相对产沙量的变化。梁峁坡耕地大面积退耕后,短期内流域产沙量不但没有减少,反而有所增加;沟间地输沙模数和相对产沙量迅速减少,沟谷地输沙模数和相对产沙量增加。1994～1996年3年的输沙模数为29650t·(km~2·a)~(-1),是该流域多年平均输沙模数13413t·(km~2·a)~(-1)的2.2倍。沟间地输沙模数不断下降,从1994年的14335 t·(km~2·a)~(-1)下降到1995年的7034 t·(km~2·a)~(-1)和1996年的3517 t·(km~2·a)~(-1),沟谷地平均输沙模数变化于44944和62136t·(km~2·a)~(-1)之间,远高于1993年前的21118 t·(km~2·a)~(-1)。沟间地相对来沙量从1994年的23％减少到1995年的15％及1996年的6%,而沟谷地相对来沙量从1994年的77％增加到1995年的85％及1996年的94％。退耕后耕作上逐渐密实,抗蚀性增强,侵蚀减弱,但土壤密实后入渗率降低,梁峁坡地产流量增加,梁峁坡地流入沟谷的径流量加大,加剧了沟谷地的冲沟侵蚀和重力侵蚀,沟谷地的侵蚀量和相对产沙量增大,从而导致流域产沙量增加。
According to the comparison of sediment deposition and 137Cs contents in dam banks before and after 1993 in Zhaojiagou watershed, the relationship between the sediment yield and the sediment yield in valley and gulch The amount of change. After a large area of cultivated land has been returned to farmland in Liangge slope, the sediment yield of the watershed not only has not decreased, but has increased in the short term. The sediment yield and relative sediment yield decreased rapidly between the ditch, and the sediment yield and relative sediment yield increase. The sediment transport modulus for the three years from 1994 to 1996 was 29650t · (km ~ 2 · a) -1, which was the mean annual sediment transport coefficient of 13413t · (km ~ 2 · a -1) 2.2 times. The sediment transport modulus between ditches has been declining from 14335 t · km ~ 2 · a -1 in 1994 to 7034 t · km ~ 2 · a -1 in 1995 and In 1996, 3517 t · (km ~ 2 · a) -1, the average sediment transport modulus in the valley changed between 44944 and 62136t · (km ~ 2 · a) -1, much higher than Before 21118 t · (km ~ 2 · a) -1. The relative sediment concentration in the ditch decreased from 23% in 1994 to 15% in 1995 and 6% in 1996, while the relative sediment concentration in the gulch increased from 77% in 1994 to 85% in 1995 and 1996 Of the 94%. Tillage after returning farmland to gradually dense, enhanced corrosion resistance, erosion weakened, but the soil after the infiltration rate decreased density, Liang Slope slope land productivity increases, the slope of the slope into the valley runoff increased, aggravated gully erosion gully And gravity erosion, erosion and relative sediment yield increased in the valley, resulting in increased sediment yield in the basin.