5　Conclusion

(1)The water resources supply and demand balance model at plain river network region with multi-water sources and multi-node is constructed.When calculating the water supply and demand balance of Three rivers subarea and Yangtze River subarea,take the control area of water source project as calculation unit,and calculate by every ten days,every river reach and every node.In the Reservoir subarea and the Lake subarea,the control area of a single reservoir and a single lake is taken as the calculation unit,and the storage and transportation calculation is carried out.It provide a new method to the calculation of water resources supply and demand balance in plain river network area,especially the handling method of the river reach at three rivers in Jingnan has important significance to that river reach whose intake discharge cannot be ignored to the total inflow of this river reach.

(2)The irrigation guarantee rate of each irrigation district is analyzed by taking the irrigation district as analytical unit.Generally speaking,the irrigation guarantee rate of irrigation district with the Yangtze River as the main water source is high,and since the irrigation district with three rivers in Jingnan as the main water source is affected by the decrease of split flow,the irrigation guarantee rate shows a downward trend with time.In the meantime,analyzes the water shortage rate and irrigation guarantee rate of every irrigation area by taking each calculated subarea as a unit,and clarifies the water shortage link of irrigation districts.Thus,it provides a new idea for the analysis of water supply and demand balance in multi-water source irrigation districts.

(3)The generalized treatment of the calculation nodes and deep sink is valuable for the analysis of water supply and demand balance and the allocation of water resources for regions like plain river network area.