Assessing The Effects Of River Ecological Restoration Based On A Biological Indicator (Dragonfly)

Growing demand for water reduce the river water with the fast development of the domestic economy, the channelization of the river make the river not continuity, and influence water quality. rivers ecosystem’health influence the development of economy and the survival of mankind and the stability of the ecological and the sustainable development of the country directly. Country like South Africa, the United States and Britain had carried out some work about river health assessment in both the time scale and space scale. But more people didn’t realize the importance of river health in early days. more and more problems about river healthy increasingly prominent.This has attracted the attention of country and related domain experts and gradually formed the different methods of river health assessment.River health assessment methods play an important role for river management scientifically and continuously. By river health assessment, we can evaluate and get background information at the situation of the river objectively. Then it can guide how to restore the river.reference for river health assessment methods at home and abroad, this paper will take river assessment about river restoration in Erdao District of Changchun CityThis paper use Dragonflies as indicator and combine with Habitat composite index to assess river restoration and non-restoration river. Then comparative the effect of the two rivers, for the river of restoration had taken different restoration measures. So we use the same way to assess the effect of different estoration measures. The main results are:1. Assessing the effects of river ecological restorationBy the contrast analysis of the environmental elements of contrast rive(non-restoration river) and the experimental river (river ecological restoration), including physical and chemical factors and vegetation index,we can get that by ecological restoration for the experimental river, the physical and chemical factors have changed dramatically, riparian plant species, quantity, diversity, and plant coverage has improved significantly, the cover degree get reduced.By evaluating the habitat comprehensive index, the average index of the contrast rive habitat is87.8, the habitat of the experimental river averages130.6, the two of them stand the worse and better level in the evaluation system of classification standard; the experiment of the better river habitat quality shows up in the stability of river embankment and less damage to the bank; it has a great change of the water yield, and covered70%of the river; it has high diversity of vegetation, more than50%of the area on the banks was covered by the plant; the habitation is complex, it has aquatic vegetation, litter, wood, stone and many sorts of small habitat, due to the experiment river using a variety of repair measures based on a variety of purposes, and build the diversity of river structure, the quality of the river habitat has improved, so the restoration effect is significant.Contrast river appeared totally52dragonflies, including1genera,2species,1family, only one dominant species of them in it; Experimental river dragonflies totally appeared954, including6genera and4families,9species, there are four dominant species in it; from many aspects like diversity index, species and amount of dominant species, Experimental river dragonflies are higher than contrast dragonfly corresponding index of the river.2. The assessment of the effect on three repair measures to the riverThere are no significant difference of velocity on different repair measures of physical and chemical factors like wetland restoration measures and the spur dike repair measures, all three index are high including hydraulic drop repair measure of flow velocity, spur dike repair measure of the river water level, drop water repair measures of pH. the measure index of the river banks of the wetland restorations is higher than the spur dike repair measure, no matter on the plant diversity index, species or quantity, but the plant coverage is on the contaray.The habitat composite index of the large wetland restoration measures river, the river of spur dike repair measures and plunge repair measures of river are152,129and110, according to the classification standard of comprehensive index evaluation system of the north river habitat, it was generally divides into three levels like good, better and common. The river of wetland restoration measures and the spur dike repair measures river Banks are stable, and got many types and volume of riparian vegetation, so the characteristic of them are variety kinds and large numbers, large river water, many microhabitat, high habitat complexity, etc. On exists in repair of the river, the damage is serious, riverbank the soil collapse rate is high, the soil erosion is serious, the lower riparian plant diversity.There are totally475dragonflies appeared in the river of wetland repairing including9species,6genera and4families, four of the dominant species among them; the river of spur dike repairing has got totally430dragonflies including3families,5genera and8species, there are two kinds of dominant species; the river of exists measures got318dragonflies including13genera,6species, and one of the dominant species. Whatever the families, genera or species, the river of wetland restoration are more than the spur dike repair river. On the same aspects, the dragonflies in spur dike repair river are more than the river of plunge in repair. Through biological diversity index analysis, the dragonflies in wetland restoration measures is higher than the spur dike and plunge measures to repair, and spur dike repair measures of biological diversity index is higher than the repair river, the mainly severely damaged part is existes repair measure.All three kinds of river parts are benefit for the habitat of the dragonfly, but wetland restoration measures of the river and spur dike repair measures river is more suitable for dragonflies, it showed that the effct of measures of wetland restoration of repairing river is better than that of spur dike repair river and spur dike repair measures, and the repair of spur dike is better than existes repair repair measures, based on the concept of ecological restoration and combining with engineering measures the drop repair measures river need to be continually repaired.