Abstract:

In recent years,the upstream Longtan Reservoir in Xijiang watershed is used to regulate the downstream Wuzhou flow in dry season for the purpose of saltwater suppression.This method has proved to be an important engineering measure to ensure the fresh water supply in the Pearl River Estuary area in dry season.In this paper,the reservoir discharge and the interval watershed runoff process between Longtan and Wuzhou are considered together as a whole and the rainfall-runoff of the non-controlled interval basin is modeled by using the digital watershed mo-del.Then,numerical experiments are carried out to analyze the response of Wuzhou flow rate to Longtan discharge affected by the watershed runoff process.The results show that（1） as a major component of Wuzhou flow in dry season,Longtan reservior discharge is linear to Wuzhou flow rate;（2） the lowest discharges for saltwater suppre-ssion are respectively 600 m³/s and 800 m³/s in dry years and bias-special dry years;（3） the flow response patterns of Wuzhou flow rate are related to the upstream discharge scale as well as to its changes over time;and（4） large discharge with rapid change may result in short response time.

Key words: dry season, runoff, digital watershed model, reservoir discharge, saltwater suppression, flow regulation