Rivers play a key role in ecosystems and society, and they provide a range of ecosystem functions such as shelter and food source for an array of biological species, aid in flood management and ecological refuge development. Socially, rivers accommodate communities by providing a medium for transport, recreation, tourism, worship, ecosystem services and a place to experience the serenity of nature Tumen River is an international river which located in the national boundaries of China, North Korea and Russia. With the three countries have different management and policies, it has been being seriously destroyed by various human activities including contaminant discharge, damming, solidifying riverside, destroying vegetation in the riparian zone and etc., resulting in deterioration of water environment, degradation of biological communities and riverbed atrophying It brings bad affection on the social and economic development of Tumen River Basin area which also affects and restricts the regional economic development. Therefore, the restoration and maintenance of "healthy" river ecosystems have become important objective of river management.
In this paper, we summarize the current health conditions of national and international river ecosystem, and establish an evaluation system for ecological health, which is suitable for the river ecosystem in Tumen River Basin. The system includes an objective layer, a rule layer with 5 factors and an index layer with 22 defined indexes. The objective layer generalized to the river health highly, reflecting the total level of the healthy condition of river by the river health index(RHI).The rule layers, which consider the river hydrology, river morphology, riparian zone, water quality parameters,aquatic organisms, reflected the river health attribute and level from different sides. The index layer included 22 qualitative and quantitative evaluation indicators. In this system, a health assessment index for river ecosystem is constructed based on five health stage criteria: primary health(81 < RHI < 100);health(61 < RHI < 80);sub-health(41 < RHI < 60);poor(21 < RHI < 40);worse(0 < RHI < 20).According to the evaluation index system, the weight of each index is calculated using an analytic hierarchy process and then the final index value calculated using with the method of weighted average. Then samples are collected at 25 sites of Tumen River Basin.The result shows that the RHI of all sites are between 45.59-92.84. Based on the systimetic assessment, the assessed sites are categorized into 6 sites are in‘primary health’condition, about 24 percent, 12 sites are in ‘health’condition, about 48 percent and 7 sites are in‘sub-health’condition, about 28 percent. The sites in‘Poor’and‘worse’condition is occupied zero. The results show that the river health condition in the Area of Tumen River Basin is in ‘health’ level on the whole.Using the 25 points of information, the correlation among RHI and river hydrology, river morghology,riparian zone, water quality parameters, aquatic organisms is analysed in the spss software.The results show that there is a significant correlation with RHI and aquatic organisms, Water quality parameters, river morphology, riparian zone (P < 0.05), the correlation coefficients are 0.847, 0.757,0.740, 0.547.There is significant correlation between RHI and,aquatic organisms indexes of fish resources and FCC; Water quality parameters of BOD,COD_MN,COD;River Hydrology indexes of flow condition, riparian zone of vegetation diversity indexs (P < 0.05).Strategies on river protection, recovery and sustainable development in the area of Tumen river ecosystem are proposed with the analyses of related threats. River ecosystem in this region needs science-based conservation and management.