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(一)基本情况我国黄土高原无定河中、下游的峁状丘陵沟壑区,水土严重流失,地形极为破碎,再加人口密度大,经济生活贫困,为急需重点治理与难于治理的地区。以具有代表性的米脂县泉家沟为例:该沟为无定河水系的二级支沟.主沟道长4.13公里,汇水面积5.19平方公里,海拔高程937～1147.5米。除主沟外全流域有三级小支沟18条,其它四级毛沟更多.沟壑密度每平方公里达4.66公里,形成较大山峁38个.
(I) Basic Situation Severe soil and water loss in the gully-shaped hilly and gully regions of the middle and lower reaches of the Loess Plateau in the Loess Plateau are extremely fragmented. Coupled with the large population density and poor economic living conditions, there are areas that are in urgent need of major and difficult governance. Taking the representative Quanjiagou of Mizhi County as an example, this ditch is a secondary branch trench of the Wuding River system, with a main channel length of 4.13 kilometers and a catchment area of 5.19 square kilometers with an elevation of 937 to 1147.5 meters. In addition to the main ditch, there are 18 small tributaries of three levels in the whole basin, and the other four ravines are more. The density of gullys reaches 4.66 kilometers per square kilometer, forming 38 large ravines.