南水北调中线水源地汉江上游流域主要生态环境问题及对策

汉江上游是南水北调中线水源地，流域生态环境建设是保障水源地水质安全的关键。针对上游流域水环境污染、土地利用以及水土流失等重大生态环境问题，结合流域数字高程模型及水质调查对其进行了系统分析。结果表明：（1）丹江流域、库区流域及汉中盆地水质较差，CODMn和氨氮成为水源区主要污染物；（2）各子流域区植被覆盖占各自面积的712%~957%，表明流域植被覆盖较好，但沿河岸100 m范围内农业用地占292%~434%，且多为坡耕地；（3）流域水土流失严重，2000年左右流域侵蚀图显示汉江源头、秦岭南及大巴山北均出现了大片年均侵蚀模数>2 200 t/km2的区域，且有日益增强的趋势。提出加大水环境污染整治力度、加强农业用肥管理及河岸带建设、水土保持建设以及加强流域水环境及水土保持监测和科研工作等对策。

ECO ENVIRONMENTAL CRISIS AND COUNTERMEASURES OF THE UPPER HAN RIVER BASIN (WATER SOURCE AREA OF THE MIDDLE ROUTE OF THE SOUTH TO NORTH WATER TRANSFER PROJECT),CHINA

The upper Han River basin (approximately 95 200 km2)is the water source area of the Middle Route of the South to North Water Transfer Project(MR SNWTP),thus,water conservation and eco environmental construction for MD SNWTP is of great importance. Reasonable river basin planning and management can play an important role in maintaining a sound ecological environment.In recent decades,due to anthropogenic activities and climate change,the ecosystems of the basin are degrading. Water samples were measured in October 2006,land use and land cover(LULC)pattern was characterized and water and soil erosion was determined by integrating a digital elevation model and LULC data in the paper.The results show that(1)water quality in Dan River,Danjiangkou Reservoir catchment and Hanzhong Plain is declining, and chemical oxidation demand and nitrogen are the major pollutants; (2)vegetated land cover accounts for more than 70%,while agricultural land use occupies 292%~434% in riparian zone at subwatershed scale; (3)there is increasing soil erosion,and subwatersheds with erosion modulus of more than 2 200 t/km2·a occur in headwaters,the south of Qinlin Mountain and the North of Daba Mountain respectively.The critical problems including water pollution,unreasonable land use practice and soil erosion urgently need approaches of ecological alleviation in the basin to promote environmental reconstruction.Thus,the following countermeasures are put forward:to work out waste water treatment plan and build sewage treatment plants; to manage agricultural fertilizer and construct riparian zone;to construct water and soil conservation;to establish long time water quality and soil conservation monitoring plans.