The Evaluation And Diagnosis Of River Health In Beijing Northern Mountainous Region

River is the origin of human life. It is the arteries of land ecosystem, and is also one of the important channel where the natural ecosystem material circulating and energy flowing. With the continuous development of human society, the river life and health has been threatened seriously. It is difficult to find a completely natural river which has not been interfered by human in our country now. Facing with such severe situation, it is significant to go further study the river health assessment method system and the main cause affecting the river health diagnosis for the application of river management.Under the premise of systemic research at home and abroad about river health’s theory and evaluation methods and according to the actual situation of river in northern mountainous area of Beijing, river health evaluation indicator system contains a target layer, six criteria layer,23 indicators layer had been built and the river health was divided into five grades:very healthy, healthy, sub-health, unhealthy, pathological. In this paper, the river health evaluation model of the northern mountainous area of Beijing built by the principle of analytic hierarchy process (AHP) with five-element connection number.Taking the Baimaguan river as an example, this paper use the analytic hierarchy process (AHP) to determine the index weight of various levels and then calculated river health’s level by applying the method of five-element connection number. The results showed that the sub-health and unhealthy river reach occupied two-thirds of the total, and there was no very healthy reach. Besides, the worst reach located in 17th where surround by a number of villages. According to the evaluation results on the current status ofBaimaguan river, the river health etiology diagnosis model was established to analysis the main cause of unhealthy river combining with new multivariate statistical method— partial least squares (PLS). The Results showed that in the many exogenous factors that affecting Baimaguan river health, sewage disposal has the biggest impact on the river’s status and the contribution value is 1.289, followed by a total investment of environmental protection, contribution value of 1.251. Additionally, it has positive effect on the river health. In other words, the less sewage discharge and the more investment on the river restoration, the river is more healthy.Based on the present situation of Baimaguan river, some river management advice should be put forward such as establish small sewage treatment facilities in the villages, increase the investment on the management of river ecological restoration, built comprehensive monitoring and evaluation system after river regulation, to promote the sustainable development of the river.