Study of Comprehensive Utilization of Water Resources of Urban Water Distribution Network

China is a country where the levels of water resources per capita are extremely low. With the rapid development of urbanization, water resource shortages have become a bottleneck existing in more and more cities. This study considers the comprehensive management of urban flood control, water supply, water and the ecological environment, catches the main contradiction between “water deficient” and “water rich” in cities, puts forward a comprehensive utilization pattern for urban water resources by emphasizing the utilization of rain–flood resources. After a simulation study, a better regulation pattern is brought out and achieve multiple benefits based on the river system of Gucheng Lake, which is located in Nanjing, Gaochun district, by optimizing conventional regulation. The results show that two parameters, the low water level (LWL) below which Gucheng Lake stops supplying ecological water, and the high water level (HWL) where Gucheng Lake stops importing water from rivers, are the key parameters to decide the regulation benefits, and the LWL of 9 m and HWL of 12 m is the best combination in river network regulation, the annual potential utilizable of rain–flood resources of Gucheng Lake river system can reach 57 million m3 per year, through the comprehensive utilization of the rain–flood resources, the negative effect of flood is effectively reduced and the disaster is controlled on one hand; and the water demand of urban and rural water supply, 100,000 m3/day, is effectively guaranteed as well as the regional ecological environment is improved on the other hand.

Investigation on Eutrophication Level for Gucheng Lake by the Model of Butterfly Catastrophe

Based on the field measured results in the typical periods of flood season and dry season of Gucheng Lake, the present eutrophication levels of the lake were investigated by the Model of Butterfly Catastrophe, in which series of the environmental factors were considered including the ecological indicator of chlorophylla, the nutrient indicator of total nitrogen and total phosphorus, and the physical index of water transparency. The results showed that: the water eutrophication levels of Gucheng Lake were mal-distributed in space and time; the lake eutrophication tendency in flood seasons were more obvious than that in dry seasons; the eutrophication levels in the south part of the lake were relatively lower than that in the north and the average comprehensive mutation of fuzzy membership value in the south was about 0.3006 in the dry seasons. Due to the increased pollution load and the hydrodynamic conditions, the eutrophication degree in the estuary areas were higher and the fuzzy membership value was close to 0.235, achieving the medium eutrophication level.