A Study On Construction Theory Of The Urban Ecological River And Its Application In Nantong City, China

The river where the water marches forward is the place for many kinds of life origin and multiplication, and is also the cradle of human culture. However, with the development of the social economy development, the river water resources had been utilized overly, and the water pollution was being serious day by day. Moreover, the traditional hydraulic engineering using the flinty material like concretes to protect the channel slope, had destroyed the rivers ecosystem, and leading to the water quality worsen and aquatic organism sharp declined. According to champaign river network of Nantong, urban ecological river construction theory and application was studied. The results showed:(1) Considering the total goal of ecological river construction, this article put forward ecological river construction theory of champaign river network area systematicly. At the reason of no unification definitation of ecological river, this article annotated the meaning, composition, configuration and function of ecological river.(2) Rainfall and runoff monthly distribution were asymmetry. They distributed on summer centralizely. The range of rainfall isoline is from 1040 mm to 1070mm with the distribution belt of high rainfall isoline from Nantong sluice and Jinsha to Yaowanggang sluice, and it's descending from the belt to its direction of the south and northwest with the similar descending rate. The isoline of average runoff depth is more than 300mm in the urban area and Dounan ditrict of Nantong, with the average runoff depth in other district of the studied area from 240mm to 300mm. Rainfall and runoff depth trend of Nantong were analysized by Db4 orthogonal wavelet. Rainfall and runoff depth had the similar change trend.(3) This article brought forward urban ecological river evaluating indicator system. It included water quality evaluation, riverway configuration evaluation, riverway landscape evaluation and riverway social economy evaluation. The number of evaluation index was 25. This evaluation system offered a uniform yardstick for the restoration and construction of urban ecological river. There were quantitative index and qualitative index for ecological river evaluation, and the methods of analytic hierarchy process and fuzzy comprehensive evaluation was used to evaluate the qualitative index which had high fuzziness and hierarchy in the indicator layer. Taking a case of study Hao river for example, the total ecological index of this river was calculated using this method, the results showed that the total ecological situation of this river was good comparing with the criteria of total ecological grading. The measures should be taken to improve the water quality and the ecosystem stability of this river.(4) The constructed indicator system for urban ecological river evaluating was applied to the case of typical river in Nantong by using fuzzy model. The rivers like Hao river, Jiaogang river and Ruhai river getting high score conformed to the criteria of ecological river, and some measures should been taken in the construction of ecological river to the rivers like Tongqi river, Tongyang river and Haigang river that got lower score. There were some rivers like Jiuweigang river, Tonglu river and Rengang river getting moderate score. The main influence factor to this results is water quality, so the change of water quality should be given more attention in the construction of ecological river.(5) In the case of important status of Hao river in urban river, considersing continuation of bank ecosystem, this article brought forward ecological shore protection thchnique of natural antetype, nature and artificial nature. Green areas of Hao River were designed take advantage of ecosystem integer optimization. Artifical uplevel community of adaptability and stability was established.(6) Water system transfixion and water replacement were applied to Nantong. The theory of "Open River" was applied to water control. Previous water control pattern based on construct dam and intercepte water system was spurned. This article utilizes hinge and radicalization of Hao River, realize mobilization of water. Ability of self purification of water body was improved, and then river ecological function was reinforced.(7) Hydrobiont diversity and water quality were measured before and after ecoglical river construction. The result showed that, bottom fauna of Beihao Bridge, Yuenan Bridge and Sanyuan ridge get better distinctly. Synthesis pollution index of main internal waters showed downtrend in this five years. The serious pollution of internal waters was Tongqi canal, Bingcha canal and Rutai canal. The best water quality was Ruhai River. Water quality of Hao River turned better, each cross section badder than V criterion at the beginning of ecological river construction, and accord with V and IV criterion after the ecological river construction.