Assessment Of River Basin Water Ecosystem Quality In Songhua River Basin

The assessment technique of river basin water ecosystem quality is an important technical means for grasping the water ecosystem quality of river basin and to carry out the protection measures of the river basin. At present, in our country, the research and application of water ecosystem quality assessment technology system for watershed scale based on the ecological integratiy perspective is scarce, which restricts the protection and management on water ecosystem in China. Based on the demand of water ecosystem protection in our country, this paper constructed the assessment system of river basin water ecosystem quality, and assessed the water ecosystem quality of the Songhua River basin for three consecutive years with the methods, as field investigation, sampling, identification and laboratory analysis. The mainly research achievments in the paper, as following:The assessment system of river basin water ecosystem quality was set up, based on the intecsive study of the technical framework of assessment method in some developed countries, and the field investigation of the major river basin in China. The application conditions of several evaluation methods and the technical route of selecting evaluation methods were ascertained, the selection principle of reference sites was proposed,and the selection principle and assessing technical route of biological, habitat and water quality physical and chemical index were proposed. The demostration study is being carried out on some major river basins in our country.The assessment of water ecosystem quality in Songhua River basin was studied with the assessment system constructed before.The study indicated that the Index of Biotic Integrity (IBI) was suitable to assess the water ecosystem quality in Songhua River basin. Meanwhile, the assessing index of water ecosystem quality in Songhua River basin were composed by six biological index, ten habitat index and eight water quality physical and chemical index. Moreover, the study found that Tubifex, Limnodrilus, Plecoptera, Polycentropus, Viviparus chui Yen were the characteristic indicator organisms in Songhua River basin which can indicat the condition of water ecosystem quality of the basin.The assessment study showed that from 2012 to 2014, in the Songhua River basin, the water ecosystem of 27.4% of the regional was excellent and good,22.7% was the general; 49.9% was poor and very poor averagely, The water ecosystem in the nearly half of the river basin was damaged on different degrees. The habitat quality of the river basin was mainly in general and good condition, and the water quality was maily in III class water quality standard. From 2012 to 2014, the overall water ecosystem quality of the river basin was slowly recovering and improving, and the worst area was decreasing year by year. On the whole, from good to bad, the water ecosystem quality in this basin was Heilongjiang> Songhua River downstream> Second Songhua River> Nenjiang> Songhua River upstream. Secondly, the analysis of pressure disturbance in the river basin revealed that chemical pollutants as CODMn, BOD5, COD, NH3-N, TN, TP were the main factors affecting the water ecosystem quality and the status of the biological community in Songhua River basin.The efficiency verification analysis of applicability of the assessing method was carried out, using the assessment study in Songhua River basin. The analysis showed that the assessing method could effectively distinguish the water ecosystem quality on undisturbed and disturbed sites, which indicated that the determination method of reference sites proposed in the system was reliable and reasonable, and applicative for the water ecosystem quality assessment for watershed scale. Meanwhile, the efficiency verification also comfirmed that the assessment index and assessment system were efficient, which were applicative for assessing the water ecosystem quality in Songhua River basin. In addition, the optimum proposal were proposed for monitoring and supervising system on river basin water ecosystem quality, on the evaluation system optimizing and improving, evaluation plan developing, the reference site determining, and efficiency verification analyzing.The research results can provide technical support for the construction and extension of assessment system of river basin water ecosystem quality, and provide scientific basis for the restoration and improvement of the water ecosystem in Songhua River basin.