| With the rapid social and economic development around upstream of Han river and construction of the Ankang reservoir,the ecological issue is becoming intensive and the river ecological environment facing serious risk.Till now,the literatures about planktos,zoobenthos and fish were rare.In order to effectively protect the aquatic organisms and ensure the sustainable resource utilization and sustainable environment development,it is necessary to conduct research on the aquatic ecology.With the principle of highlighting key points,this paper deeply investigated the effect of Ankang reservoir on the aquatic environment.Meanwhile,the rehabilitation effect on aquatic ecological system by Yinghu Nature Reserve.This paper put forward the artificial wetland technology for the treatment of rain sewage overflow and conducted pilot-scale research.Finally,based on emergy theory,this paper analyzed the economic value and sustainability of the two wetlands above.The construction of reservoir and the establishment of Yinghu Nature Reserve had significant influence on the aquatic environment.The existence of Ankang reservoir deteriorated the water quality in the reservoir,with DO、BOD5 and heavy metal concentration only reaching the class III standard of surface water and NH3-N,TP,Se4+,phenol and E.coli beyond the standard.After the establishment of Yinghu Nature Reserve,all the items detecting in each monitoring section met the requirement of class II standard except for NH3-N,which was close to class III standard.The water quality was obviously superior to the one in 2000.In order to control the pollution of drainage overflow in the towns around Ankang reservoir,this paper developed a novel 3-stage water-fall wetland which was settled at the end of the drainage system in the town.It was found that the DO concentration was higher and distributed more considerably in the water-fall wetland.COD,NH3-N,TN were larger reduced than in the ordinary wetland.If this wetland were widely employed round the overflow sites of water treatment plant in Ankang,30%of the pollutants in Ankang reservoir could be removed.It would be beneficial for the surface source pollution reduction,improving the water quality that flow into the Ankang reservoir and protect the security of drinking water quality.As for the water temperature,the average value changed little after the establishment of Ankang reservoir but the highest temperature decreased 3.9℃ and lowest temperature increased 1.2℃.The water temperature return the status before the establishment of Yinghu Nature Reservoir,indicating its high heat capacity and strong ability to regulate the climate.The construction of reservoir and of Yinghu Nature Reserve had significant influence on the population sized and structure of phytoplankton,zooplankton and zoobenthos.For the phytoplankton,the density and population increased especially for the cyanophytes but the types decreased.After the establishment of Yinghu Nature Reserve,the population of phytoplankton increased to some extent,but still lower than the level before the establishment;For the zooplankton,the discrepancy of zooplankton class was little.The zooplankton experienced a balanced trend from Protozoa-and-rotifer-dominated and crustacean-weak composition to Protozoa-dominated composition,which was consistent with the variation of aquatic environment;For the zoobenthos,the types decreased dramatically after the reservoir was built and increased again after the Yinghu Nature Reserve was established.Yinghu Natural Reserve played a key role in maintaining the water quality and hydrology state,In the reservoir,therefore ensuring the structure of phytoplankton,zooplankton,zoobenthos.The construction of reservoir and the establishment of Yinghu Nature Reserve had significant influence on the population sized and structure of fish.According to the investigation in 2000.i.e.after the construction of Ankang Reservoir,35 types of fish were obtained,which was much lower than the 73 types investigared in 1990.After the establishment of Yinghu,53 types of fish were found.During this process,the fish population decreased and then increased.The fish density and population detected in Lanhe survey point was the largest,and it increased more significantly after the establishment of Yinghu Nature Reserve.The reason might lie in the improved water quality,which provided better Habitat and spawning site for the fish.As for the dominant species and biodiversity of fish,the larger fish detected in 1990s was rarely detected in 2000 and 2013.The diversity indexes,richness indexes and evenness index all decreased largely after the reservoir was built,which was relevant to not only water quality but also hydraulic conditions and dam.The indexes rose again,indicating the protection to the fish diversity.This paper uses emergy analysis method to investigate the sustainability,ecological servicing function and natural capital value of Yinghu Nature Reserve and 3 3-stage water-fall wetland.This research adopted various parameters,including net emergy yield ratio,sustainable development index and other indicators to analyzed the ecological sustainability for the wetland systems.By calculating and comparing with other wetland system,it is found that Yinghu Nature Reserve was in the state of medium sustainable development and close to strong sustainable development;although the sustainable index of 3-stage water-fall wetland is lower than that of the Yinghu,but still higher than other sewage treatment processes and more superior in the energy investment.Yinghu Lake Wetland and three drop type wetland could complement each other and play a collaborative effort in the purification of Ankang reservoir water and protection of Hanjiang River basin ecological security. |
