A Case Study On Ecological Restoration For The Reservoir Inflow

In this article, the damaged river, water source of ChangChun, which is at the upper reaches of reservoir Shitoukoumen near Hill LianHua in ChangChun was taken as the study subject. A experimental river which is 200 meters long was constructed by ecological engineering. The subject was completed two months later, physical habitat, status of fish habitat, riparian vegetation and soil erosion were researched primarily. The survey data which was analysed showed that:1. Through the investigation and contrast of watercourse in the three experimental areas (maked A,B,C) and control area, it shows that the permeable dam laid by stones and timbers can influence the water flow and riverbed soil erosion and sediment, change the monotonous structure of the riverbed, form physical habitats which abounds a variety of flow rate, water depth, riffle, step-pool. Through the study of rate of permeability, the water outlet numbers of the dam, the different locations of the dams, it shows that they can form a variety of physical habitats which have different water depth, flow rate, ford and deep pool.We investigated the particle size of the riverbed sediment and adopt index k as the evaluation of river physical habitat suitability. Because of that the experiment river has just been built and riverbed sediment has not been restored to a higher level, and physical habitat has not reached the high lever. So the index k in the experimental area is slightly lower than those in the control area. But in the experimental areas and the control area, the index k of sandbar area is higher than the one of deep pool area.2. Through the investigation of the fish in the experimental river, there are lots of fish in the step pool but few in the riffle. We can not survey the fish in the control area because of the terrain restriction; it shows that: (1) a few fish can also be found in the observing region (2) fishes usually prefer to live in the closed space formed by the lodging of riparian vegetations.Through the investigation and analysis between experimental area and control area, we know that fish usually lives in the areas which consist shade, rich food and deep water. Because of a variety of habitats formed by deep pools, rock shelters, as well as closed space, the area of ford-deep pool provides a nicer habitat for fish and are more suitable to survive than control area.3. Through the investigation and analysis, riparian vegetation total coverage in the areas near water and ones removed water of square 1 is respectively 85% and 73%, but the total coverage in the areas near water and ones removed water of square 2 is respectively 51% and 48%. The frequency of native species of square 1 is higher than the one of square 2, but the frequency of Medicago sativa L. is 100% in both square 1 and square 2. However, the frequency of Salix matsudana Koidz and Phragmites australis in the square 1 is less than that in square 2 , both of the frequency do not reach to 100%, at the same time, expect Artemisia annua L., the frequency is all 100% . The number of species and the biodiversity in the square 1 is higher than that in square 2 , and the biodiversity in the square 1 near the river is higher than the control area.According to the analyzing results above, we can see: owing to surface soil which is filled back, the riparian vegetations in the square 1 has been restored in a relatively short time. The index of total coverage, the frequency, the number of species and the biodiversity are higher than square 2 where surface soil is not filled back. So, when carrying out ecological restoration of rivers, surface soil backfilling that can make vegetations at the land/inland water acetones restore well in a short time is an economic and practical method.4. The experiment proved the thickness of soil erosion is respectively 0.3cm in square 1, 0.4cm in square 2 and 0.4cm in control area and the amount of soil erosion is respectively 3750 t?km-2 in square 1;5000 t?km-2 in square 2 and 5000 t?km-2 in control area between Aug and Sep. As a result of topsoil backfill in square 1 and the vegetation recovery is better than square 2,so the riparian effect of anti-soil erosion is: square 1 > square 2. Compared with the experimental areas, the control area occurred partial collapse in the riparian toe of slope due to no bank strengthening, but the experimental areas were calm. Although the experiment was in a short period, the technology that mechanical components coupling plant components can effectively prevent soil erosion, reduce soil and water loss. And the higher the vegetation coverage is, the stronger the effect of anti-erosion is.