北京市北沙河上游典型小流域水环境治理措施的生态效益分析

Study on ecological benefit of water environment control measures in typical small watersheds of Changping District,Beijing

北京市属于资源型重度缺水地区,水资源紧缺严重制约其可持续发展,加之水质恶化,造成了全市水资源和水环境形势严峻的局面.为此,北京市布设相应措施对小流域水环境问题进行治理,分析治理措施的生态效益能够为小流域水环境治理措施的合理布设提供科学依据.以北京市昌平区北沙河上游8条小流域为研究区,基于InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)模型定量估算了研究区在实施治理措施前后的地表径流、洪峰量、泥沙输移和水质污染(磷输出和氮输出)4类生态指标的变化,分析了治理措施的实施对研究区水生态的改善程度.结果表明:①研究区范围内年地表径流由275955.52 m^(3)∙km^(-2)降低到274965.69 m^(3)∙km^(-2),共减少了0.0026%;②全年洪峰量减少了0.068%,生态系统的洪水调节能力得到改善;③泥沙输移总量由1691157.24 t∙km^(-2)降低至1567156.48 t∙km^(-2),减少了7.3%,各小流域防止泥沙淤积的能力得到提升;④磷输出减少了7.6%,氮输出减少了4.4%,生态系统的水质净化服务显著提高.

Beijing suffers severe water shortage,which inhibits the regional sustainability.Additionally,the deterioration of water quality resulted in the grim situation of water resources and water ecology.Beijing set up relevant measures to deal with hydro-environmental issues in small watersheds.The research on the benefits of these management measures will provide a scientific basis for the reasonable layout of management measures.This paper analyzed 8 watersheds in the upper reaches of Beisha River in Changping District,Bejing.Applying InVEST(Integrated Valuation of Ecosystem Services and Tradeoffs)model,4 ecological indicators,namely the annual surface runoff,flood peak,soil erosion by water,and water pollution(nitrogen output and phosphorus output)of the study area before and after the measures were estimated.Based on that,the improvement of the water environment in the study area by the implementation of the treatment measures was analyzed.The results showed that:①The annual surface runoff in the study area decreased from 275955.52 m^(3)∙km^(-2)to 274965.69 m^(3)∙km^(-2),a total decrease of 0.0026%;②The annual flood peak decreased by 0.068%,and the flood regulation capacity of the ecosystem was improved;③The total sediment output decreased by 7.3%from 1691157.24 t∙km^(-2) to 1567156.48 t∙km^(-2),and the capacity of preventing sediment deposition was improved;④Phosphorus output decreased by 7.6%while nitrogen output decreased by 4.4%.The water purification of the ecosystem has been significantly improved.