Water shortage and countermeasures of irrigation area around Lake Poyang in dry seasons

Abstract

近年来，在以三峡大坝为代表的一系列流域人类活动作用下，鄱阳湖出现了枯水期延长、水位提前消落的现象，导致了一系列生态环境和民生问题.本文从环湖灌溉缺水入手，采用11种概率分布分析1953—2018年星子站水位，进行比较优选后选择Wakeby分布作为理论分布，得到90%保证率下的湖泊年平均水位及枯季9月至翌年2月月平均水位，并据历年平均水位选取代表水文年，进行环湖灌区水资源供需分析，获得缺水量.在此基础上，建立灌区缺水量变化与长江干流流量变化的量化关系，讨论其应对策略.结果表明：自2003年三峡工程运行以来，由于湖泊枯季水位降低，90%保证率下鄱阳湖环湖灌区9月至翌年2月的缺水量已达到2.26亿、2.12亿、0.57亿、0.58亿、0.55亿、0.25亿m³.通过调节长江干流流量满足环湖灌区用水需求的方案受到时段和“五河”来水状况的限制，即该方案仅适用于枯季9—10月“五河”来水减少的情况下.受限于这些条件，调节长江来水并非治本之策，目前仍需采取其他更为有效的手段以恢复鄱阳湖的水位及其过程.;In recent years, due to the influence of a series of human activities around the river basin represented by the Three Gorges Dam, the dry season duration of Lake Poyang was prolonged and early drawdown of water level was observed. This leads to a series of ecological and livelihood issues. To investigate the water shortage of irrigation around the lake, this paper analyzed the water level of Xingzi Station from 1953 to 2018 by applying eleven probability distribution functions. The Wakeby distribution was selected as the theoretical distribution after comparison. Both the mean annual water level and mean monthly water level during the dry season under a 90% guarantee rate were obtained. Based on the mean annual water level over the years, the representative hydrological year was selected to analyze the supply and demand of water resources, thus the water shortage was obtained. Consequently, the quantitative relationship between water shortage change of the irrigation area and water discharge change of the main channel of Changjiang River was established, and the countermeasures were discussed. The results show that the water shortage (under 90% guarantee rate) of irrigation area around Lake Poyang has accordingly reached 226 million m³, 212 million m³, 57 million m³, 58 million m³, 55 million m³ and 25 million m³ from September to February of the next year, since the operation of the Three Gorges Dam in 2003. The solution to meet the water demand of the irrigation area by regulating the water discharge of the main channel of Changjiang River is only applicable to the situation when the water discharge from the ‘Five Rivers’ decreases in September and October. Therefore, to restore the water level of Lake Poyang and its process, other more effective means are needed.