灌区干支渠渗漏估算方法及其在水资源优化配置中的应用

为解决大尺度农业水资源规划中遇到的渠道渗漏估算精度低且估算方法不符合渠道渗漏机理问题,该研究在对前人的研究成果与渠道渗漏关键要素进行分析基础上提出了渠道渗漏估算方法。根据提出的渠道渗漏估算方法,渠道渗漏系数通常是随渠道引水量变化的单调函数,传统方法中使用固定的渠系渗漏系数方法在渠道引水量变化时会对渠道渗漏量有一定程度的低估和高估。为进一步验证不同的渠道渗漏估算方法对于农业水资源优化配置的影响,以甘肃省黑河中游17个大中型灌区的水资源优化配置问题为例,建立了农业水资源多目标随机规划模型对有限水资源进行合理分配。模型同时选择了渠道渗漏估算方法与传统的固定系数方法。优化结果显示,使用固定渗漏系数的传统方法不能体现黑河中游灌区干支渠的渠道渗漏系数随渠首引水量的动态变化关系,使用固定渗漏系数方法可能会导致对渗漏量的估计产生10%以上的偏差,进而影响实际的田间可用水量、预期产量、预期收益的估计,使得优化目标不能真正实现。同时,对比研究发现,当可用地表水量发生改变时,渠道渗漏估算方法可以更好反映出渠道渗漏率动态变化,为农业水资源规划提供更加精确的水量信息,增加了水资源规划方案的有效性与可行性。

Method for estimating trunk and branch canal leakage in irrigation districts and its application in optimal allocation of water resources

Abstract: The water shortage crisis caused by population increase and climate change threatens China''s food security and ecological health. How to improve the utilization efficiency of water resources in agricultural production and promote regional sustainable development are main problems faced by agricultural water managers. In agricultural water distribution process, canal leakage is one of the important water consumption sources. Traditional methods usually use a fixed canal leakage coefficient in planning water resources, which affected the estimation accuracy of canal leakage. Therefore, it is of great significance to accurately estimate the leakage of main and branch canals for guiding the construction of canal engineering and formulating effective optimal allocation scheme of agricultural water resources. In order to improve canal leakage estimation accuracy for large-scale agricultural water resources planning, this study proposed a method for estimating the canal leakage based on analyzing the previous researches and the key elements affecting canal leakage. According to the method proposed in this study, the canal leakage coefficient had the dynamic relationships with water amount of canal diversion. The method proposed by this study was compared with the traditional fixed canal leakage factor method to further verify the impact of different canal leakage estimation methods on the optimal allocation of agricultural water resources. Both methods were applied to the middle reaches of the Heihe River. In the study area, the water managers had to optimally allocate limited water resources among 17 large and medium-sized irrigation districts. A multi-objective stochastic programming model with three objectives (including maximum economic benefit, irrigation water use efficiency, and irrigation water productivity) was established for optimizing limited water resources allocation. Available water resources, crop water demand, and food security were considered as constraints of the optimization model. After collecting the necessary data and solving the optimization model by minimum deviation method, optimization results were obtained. The results showed that the optimization results obtained by the traditional method with fixed leakage factor may underestimate the canal leakage loss in the middle reaches of the Heihe River, leading to more than 10% deviation in estimating the leakage. The underestimation may further affect the field water availability, the expected output, and the estimation of the expected profit, making the optimization goal impossible to achieve. When the available surface water changed, the canal leakage estimation method proposed in this study better reflected the dynamics of canal leakage rates, providing more accurate water quantity information for agricultural water resources planning as well as increasing the effectiveness and feasibility of water resources planning schemes. The method proposed in this study can provide an effective tool for the fine management of agricultural water resources and help the development of agricultural water saving.