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1“丘三区”的环境区域特征及水土流失状况陇中黄土高原“丘三区”位于甘肃省的洮河以东、六盘山以西、西秦岭以北和宁夏回族自治区南部的部分地区,面积4.855万km~2,总人口851.1万,人口密度为175.2人/km~2,为黄土高原人口较稠密的地区之一.该区大部分属于甘肃省中部干旱半干旱地区,多年平均降水量在316～650mm之间,其中7～9月份降水量占全年的55.0%～68.8%.该区在侵蚀地貌上属于黄土丘陵沟壑区的梁状丘陵,沟蚀及重力侵蚀比较活跃.区内较大的水系有渭河及其支流葫芦河、散渡河、牛头河以及黄河支流祖厉河、洮河等.该区年径流模数1.5～12.0万m~3/km~2,土壤年侵蚀模数3300～9500t/km～2,其中散渡河上游部分地区可达到10000t/km~2以上,是黄土高原严重水土流失区之一.
1 Environmental Characteristics and Soil and Water Loss Status of “Qiusan District” Longqiu Loess Plateau “Qiusan District” is located in the east of Bahe River in Gansu Province, west of Liupan Mountain, north of West Qinling Mountains and parts of southern Ningxia Hui Autonomous Region. Its area With a population of 8.511 million and a population density of 175.2 persons / km ~ 2, which is one of the more densely populated areas in the Loess Plateau. Most of the area belongs to arid and semi-arid areas in central Gansu Province. The average annual precipitation 316 ~ 650mm, of which precipitation from July to September accounted for 55.0% ~ 68.8% of the whole year.The area belongs to the loess hilly gully area on the erosion landscape, and the gully erosion and gravity erosion are relatively active. The major water systems are the Weihe River and its tributaries Huluhe, Sanhe River, Ngau Tau River and the tributaries of the Yellow River, Zuli River and Taihe River, etc. Annual runoff modulus of this area is 1.5-12.0 m 3 / km 2, and annual soil erosion modulus 3300 ~ 9500t / km ~ 2, of which the upper reaches of the part of the river can reach more than 10000t / km ~ 2, is one of the serious soil erosion in the Loess Plateau.