New Approach To Assess The Aquatic Effects Of Watershed Socio-economic Development And Its Application In Lake Nansihu

Recently, under support of a relatively good water and soil resources endowment,socio-economic activities of watersheds (population, urbanization, GDP, water andsoilresources developmentintensityetc.) showed a rapid development trend with greatlyaccelerated urbanization change. Thereby the pollution load of pollutants have increasedalong the expansion of economy, including industries, municipal sewage, agriculturalpollution sources, urban storm water and atmospheric deposition, which directly orindirectly deteriorated the aquatic and water ecosystems. Despite the increase quantity ofwatershed water pollution prevention and control measures in China, the aquaticdegradation is still accelerated by local improvement. At present, China has faced anoverall improvement of water environmental degradation with a small proportion improved.With environmental pressure continuing to increase, the situation remains grim.Consequently, it is necessary to accurately and objectively carry out the assessment of theaquatic effects of watershed socio-economic development, in order to guide theimplementation of watershed sustainability.This research aims to support China’s lake assessment and identify potentialsolutions.A new approach is proposed to assess the aquatic effects of watershedsocio-economic development, which can be summarized as “Drive (socio-economicdevelopment)-Pressure (water pollution load)-State (water quality)”, logically only showed“forward effects”; in addition,“backward feedbacks” response based on system dynamicsmodel was applied in this study to interpret the plight: effects of implementation ofwatershed water prevention and control measures are not immediately reflected in the“state” of aquatic; on assessment time scales, the cognitive framework is combined withthe current conditions and future trend, concerning the static level of historical or currentsituation and its future dynamic evolution trend of information, from the perspective of thedynamic development of socio-economic relationship with the environment; on assessmentcontents, assessment results are used to achieve socio-economic regulation approach,direction and strategic choice; on index system, which should be based on the “watershed socio-economic-aquatic” and multivariate analysis to embody the aquatic effects ofwatershed socio-economic development of “forward effects” and “backwardfeedbacks”,so as to provide an available, independent and significant set of“Pressure-State-Response” index; on assessment methodologies, assessment criteria, grade level anduncertainty estimation are updated and clarified systematically for the proposed assessmentapproach.Lake Nansihu, one of the lakes in China with good water quality, was selected as astudy case. The results indicate that (i) the conceptual framework is effective in rapidlyidentifying the necessity, potential, direction and threshold of watershed-scalesocio-economic regulations;(ii) the assessment index for Lake Nansihu was improvedfrom level IV at2000to level II at2010, however, it would decrease slowly in next20years and fluctuate around level III in a long run; and (iii) it is suggested to lower thedeveloping rate at2030to be about75%of the average rate in past11years so as tomaintain the assessment index of level I according to the assessment criteria.