The ecohealth assessment and ecological restoration division of urban water system in Beijing

Assessment of Ecological Environment Quality for Urban Sustainable Development Based on AHP

Cities are gradually developed on the basis of adapting and transforming the natural environment. In a certain urban area, human activities, natural environment, and other factors and their mutual influence constitute the urban ecological environment. Therefore, the evaluation of urban ecological environment quality is of great significance to the analysis of urban development. This paper takes a city in Western China as the evaluation object, uses AHP to determine the index weight, reasonably analyzes the current situation of the urban ecological environment, and further comprehensively evaluates the quality of the urban ecological environment. The study shows that from 2013 to 2018, the comprehensive capacity of the city's ecological environment quality showed a steady upward trend, except that the natural disasters of floods and mudslides in 2014 had a certain degree of fluctuation. The comprehensive index of ecological environment quality has increased from 0.337 in 2013 to 0.412 in 2018. The overall level is still low, but the development speed is relatively stable. The urban ecological environment has been gradually improved, and society, economy, and nature have maintained a certain degree of sustainable development.

Health Evaluation and Risk Factor Identification of Urban Lakes—A Case Study of Lianshi Lake

Health assessment and risk factor identification represent the premise and foundation of scientific management and ecological restoration of urban lakes. Based on in-depth understanding of the nature–society duality of urban lakes, a framework for evaluating urban lake health was constructed, including four modules, namely, establishing an index system; determining the index weight; identifying risk factors; and a comprehensive lake health evaluation. Employing this framework, we evaluated Lianshi Lake, Beijing, classifying the lake condition as “sub-healthy”. Based on the evaluation data, we identified the health risk factors of the lake. We applied standard difference rate (SDR) and risk degree (Rd) (safe degree (Sd)) concepts, and classified the indices of risk areas employing the Pareto analysis method. Finally, we identified the lake residence period, landscape connectivity, and eutrophication as the major risk factors in Lianshi Lake. Three factors constitute the basis of ecosystem health and are key targets of ecological restoration: the lake residence period represents the hydrological and hydrodynamic characteristics of the lake; landscape connectivity is described from an ecological perspective, and represents the integrity of the lake ecosystem; and the eutrophication states describe the water quality characteristics and represent the availability of lake water. The results contribute to decision-making for comprehensive urban lake management.

A new comprehensive ecological risk index for risk assessment on Luanhe River, China

With the enhancement of human activities which influence the physical and chemical integrity of ecosystem, it was bound to increase ecological risk to the ecosystem, and the risk assessment of small scale, single pollutant, or only on water quality have been not satisfied the demand of sustainable development of basin water environment. Based on the response relationship between environmental flow requirements guarantee ratio (GEF) and river ecological risk index (ERI), the Sediment Quality Guideline Quotient index (SQG-Q), and the Biotic Index (BI), we construct a new comprehensive ecological risk index (CERI) to evaluate the ecological risk of Luanhe River, China. According to the response relationship between GEF and ERI, upper and lower reaches of Luanhe River (Goutaizi to Hanjiaying) were at moderate risk level (0.41 < ERI < 0.56) in dry season, and all sites were at low risk level (ERI < 0.40) in wet season; considering the contribution of heavy metals contamination in the SQG-Q, the Luanhe River was the most influenced by higher levels of heavy metals in dry season and wet season; when this index was applied to the PAHs levels, only 30 and 20% of the sampling sites appeared to be moderately impacted (0.1 < SQG-Q PAHs < 0.5) by the PAHs in dry season and wet season, respectively. The results of BI showed that half of the sites appeared to be at moderately polluted level (50% of the sites, 0.25 < BI < 0.32) and heavily polluted level (Zhangbaiwan, BI = 0.36) in dry season, and 40% of the sites appeared to be at moderately polluted level (0.26 < BI < 0.29) in wet season. The CERI showed that 70 and 30% of the sites were at moderate risk level in dry season (0.25 < CERI < 0.36) and wet season (0.26 < CERI < 0.29), respectively. The results could give insight into risk assessment of water environment and decision-making for water source security.

Environmental flow assessment for improvement of ecological integrity in the Haihe River Basin, China

The Haihe River Basin is a semiarid water resources area of China. River ecosystem was degraded for high population density and intensive water resources development activities. To assist in the improvement of the ecological integrity of this river ecosystem, an environmental flow assessment model was developed that consider both spatial structure and dominant eco-function parameters. River ecosystem was divided into three sub-ecosystems which including river reach, wetland and estuary based on the spatial structure of river ecosystem. River reach was divided into three types which including habitat restoration type (HR), water quality restoration type (WQR) and vegetation restoration substitute water quantity restoration type (VRSWQR) according to their dominant eco-function. The spatio-temporal distribution of environmental flow (EF) for the river ecosystem in the Haihe River Basin was assessed based on the model. The results indicate that the EF for the river reach, wetland, and estuary are 2.267, 1.532, and 0.972 billion m(3), respectively. The EF for HR type of river reach, the WQR type of river reach and VRSWQR type of river reach are 1.140, 1.138, and 0.154 billion m(3), which are equal to 4.320, 4.312, and 0.584 % of the average annual flow of 26.39 billion m(3), respectively. EF for river ecosystem in wet period (June-September), normal period (October-January) and dry period (February-May) are 2.999, 0.951, and 0.821 billion m(3), respectively. Annual EF for river ecosystem of the Basin are 4.771 billion m(3), which accounts for 18 % of the average annual flows of 26.39 billion m(3).