Evaluation Of Water Environment Quality And Construction Of Ecopath Model In Xidayang Reservoir Ecological Restoration Project Demonstration Area

Xidayang reservoir is a large-scale comprehensive utilization reservoir in Hebei province,and as the upstream of Baiyangdian lakes,it is an important water replenishment reservoir.The quality of water environment seriously affects the water quality of Baiyangdian lakes.This study selected a library bay area in Xidayang reservoir,to establish ecological restoration demonstration area,make it become a self-maintenance,a virtuous cycle,reasonable structure of the aquatic ecosystem.In this study,the water quality and aquatic organisms of the demonstration area were investigated in May,July,September and November,the water environment quality was evaluated and the Ecopath model was constructed,the impact of ecological restoration on water environment quality and reservoir ecological balance was judged,the implementation effect of ecological restoration project was evaluated,and the improvement of the restoration project was provided with a basis.The main findings are as follows:Water quality evaluation results show that:The p H of the demonstration area is maintained at about 8.5,which is alkaline water.SD ranged from 2.6 m to 5.2 m,and DO ranged from 5.46 to 6.48.The concentrations of COD_Mn and TP in the demonstration area were reduced by 22%and 55%respectively;in May and September,the concentration of chl.a in the demonstration area was lower than that in the control area,In July and November,the concentration of chl.a in the demonstration area was higher than that in the control area;The concentration of TN,NO₃^-and NO₂^-in the demonstration area in May,July,September and November was not different from that in the control area,In May,the concentration of NH₄⁺in the demonstration area was lower than that in the control area,the concentration of NH₄⁺in the demonstration area in July,September and November was not different from that in the control area.Phytoplankton evaluation results show that:the shannon-wiener diversity index?H?,Pielou evenness index?J?and Margalef richness in the demonstration area were higher than control area in may and July.In September,the Margalef richness index of the demonstration area was higher than that outside the demonstration area.In terms of the number of dominant species,the number of phytoplankton species in the demonstration area in May and July was higher than that in the control area,the number of dominant species in the demonstration area in May was lower than that in the control area,the number of dominant species in the demonstration area in July was equal to that in the control area,and the number of phytoplankton species and dominant species in the demonstration area in September were higher than that in the control area.The number of dominant species changed from lower than control area to higher than control area.It can be seen that the establishment of the demonstration area has a positive effect on the phytoplankton diversity in the water.Ecopath model results of Xidayang reservoir demonstration area show that the nutritional level of the 16 functional groups ranged from 1.00 to 3.62;The total system flow is 12130.47 t/?km²·a?;Energy flows are mainly distributed in???between trophic levels;The energy conversion efficiency of the system was low,only 1.7%;The food web can be roughly divided into three food chains,two grazing food chains,namely phytoplankton—zooplankton and benthic animals—small fish—medium and large fish,aquatic plants—herbivorous fish and omnivorous fish—carnivorous fish.Detritus food chain:fragmental—benthic animals and omnivorous fish—carnivorous fish.According to the system connection index?CI?and system omnivory index?SOI?,the food web structure in the ecological restoration demonstration zone is relatively complex,ecosystem structure is relatively stable.The cultivation of aquatic plants in large quantities improves the primary productivity of the ecosystem.In the Ecopath model,the ecological nutrient efficiency of aquatic grass is only 0.005,resulting in a large amount of energy waste.In the next step,a certain amount of herbivorous fish can be considered to be kept in the demonstration area to improve the utilization rate of primary productivity and make the ecosystem of the demonstration area more stable.