2　General Idea of Water Resources Supply and Demand Balance

The water users in Jingnan river network mainly include water for agriculture,industry,construction industry,life,the tertiary industry and off-stream ecology,and the water sources mainly include the Yangtze River,three rivers in Jingnan,reservoirs,lakes,canals,groundwater and ponds,etc.Industrial water and construction industrial water generally have independent water intakes.Most of these industries get water from Yangtze River and underground water,whereas a small amount get water from reservoirs and three rivers in Jingnan.For those enterprises whose water resources cannot be guaranteed,they are usually equipped with groundwater backup water sources.The residents'living water,the tertiary industrial water and the off-stream ecological water are mostly provided by the waterworks,which mainly get water from the Yangtze River,the three rivers in Jingnan,the underground water,the reservoirs and the lakes.The waterworks that take three rivers in Jingnan as water source,can basically meet the demand of domestic water,though the three rivers in Jingnan may break in the dry season,because the water intake is generally located in the deep channel of the rivers.To those waterworks that cannot meet the water demand,some of them have also been equipped with groundwater back water source.Agricultural water users get water from Yangtze River,three rivers in Jingnan,lakes,reservoirs,ponds and deep canals.The agricultural users,which take three river in Jingnan,lakes and reservoirs as water sources,are inevitably influenced by industrial water and domestic water intakes.Therefore,they should be considered together.Based on these situations of water use and water source,the general idea of water resources supply and demand balance in Jingnan River network is as follows:

Fig.1　The geographical position of Jingnan River network are and irrigation districts

Note:the name of irrigation districts and abbreviation are in Fig.1

(1)Calculate and predict the water demand of agriculture,industry,construction,the third industry,the residents'living and off-stream ecology.

(2)According to the situation of water intake and water use,partition computational subareas and compute units.Among those water users,which take Yangtze River as the water source,the industrial water and domestic water are guaranteed,and the agricultural water intakes require supply-demand balance calculation.As to the water users with the three rivers in Jingnan as water source,the supply-demand balance are calculated in terms of intakes(including agriculture,industry and life water).And those water users with the reservoirs or lakes as the water source,we use reservoirs or lakes as calculation units.

(3)The sequence of water source supplying water:the pond and trench canal is prior to other water source(the Yangtze River,rivers,reservoirs and lakes).The sequence of water users getting water:calculate the supply-demand balance of the water users,which take the three rivers in Jingnan as the water source,from upstream to downstream according to the location of the intakes;and when the three rivers in Jingnan break and water is supplied only by troughs,the sequence of water supply is that the water supply for living and industry is prior,followed by water for agriculture.While the reservoirs and the lakes are water source,the sequence of water supply is that:life,industry,construction industry,and agriculture.

(4)The newly added or expanded pump stations that have been determined to be implemented are regarded as current water supply projects while calculating.