汉江流域上游生态环境现状及治理措施

Eco-environmental Status Assessment and Countermeasures in the Upper Hanjiang River Basin

汉江流域上游水源保护区主要是指丹江口库区以上的地区。汉江流域水环境保护的优劣对我国的南水北调工程起着至关重要的作用。针对上游流域水环境污染、水土流失等重大生态环境问题,结合水质调查,对沿途各县区水土流失进行了系统分析。结果表明:(1)安康水库水质呈下降趋势,特别是硝酸盐氮(NO3—N)由蓄水前的年均0.32mg/L上升至20a后的0.99mg/L以上,是蓄水前的3倍,增加了209.3%。(2)丹江口水库水质总体状况较好,除总氮年平均为Ⅳ类水,其余指标为Ⅰ或Ⅱ类。(3)流域水土流失严重,2009年安康、汉中、商洛3市水土流失模数都超过5 000t/(km2.a),安康市7县区水土流失模数高达16 352t/(km2.a),十堰市水土流失模数相对较小,但也达到了3 528t/(km2.a)。各市土壤侵蚀总量大小依次为:安康市(7县区)>汉中市(7县区)>商洛市(3县区)>十堰市,且呈日益增加趋势。应加大水环境污染整治力度,加强水土保持建设和法制建设,提高生态环境保护管理能力,加强基础设施型工程为民营工程做好环保示范。

The upper Hanjiang River basin is the water source area of the middle route of the south to north water transfer project.Thus,water conservation and eco-environmental construction in the middle route of the south to north water transfer project is of great importance.Due to serious water environment pollution and soil erosion in the upper reaches of Hanjiang River,the ecosystem of the basin is degrading.Water samples were measured and soil and water loss was analyzed based on the observed data.Results showed that（1） water quality of Ankang Reservoir declined,especially nitrate nitrogen（NO3—N） increased from 0.32 to 0.99 mg/L 20 years after water storage,increasing by 209.3%.（2） Water quality of Danjiangkou Reservoir was relatively better,but the average annual total nitrogen was in the Ⅳ grade and other indexes of water quality were in theⅠorⅡgrade.（3） Soil and water loss increased.In 2009,the total erosion modulus in the whole basin was more than 5 000 t/（km2·a）;in Ankang City（7 counties/district）,as high as 16 352 t/（km2·a）;and in Shiyan City,3 528 t/（km2·a）.The total amount of soil erosion was in the order of Ankang（7 counties/district）Hanzhong（7 counties/district） Shangluo（3 counties/district）Shiyan,which shows an increasing tendency.Therefore,the following countermeasures are put forward： strengthening water environment pollution control,enhancing soil and water conservation and legal system construction,improving eco-environmental protection management and strengthening environmental infrastructure demonstration for private engineering project.