作物灌溉设计中耗水强度问题研究

Discussion on Determination of Water Consumption in Irrigation Scheduling Design

作物需水量是制定灌排工程规划、设计、管理和农田灌排实施的基本依据,如何准确估算某一地区作物需水量是我们水利工作者经常面对的问题。工作实践中,作物需水量通常是参照《微灌工程技术规范》(GB/T 50485-2009)中作物设计耗水强度确定,该规范给出的作物设计耗水强度范围较宽泛,同时没有考虑不同地点、不同水文年和不同生育阶段作物耗水强度不同的问题,这种方法推算的某一地块的作物耗水量准确性较差,继而使得规划成果带有极大的不确定性,如果以此来进行灌溉系统的运行管理也会带来一定风险。根据这一问题,建议采用更为科学的方法确定作物耗水强度,具体方法如下:①根据当地历年降雨排频寻找典型年;②根据典型年的气象数据采用FAO-1998提出的彭曼-蒙特斯方程计算参考作物需水量,再乘以作物系数得到作物需水量;③估算当地有效降雨量,确定作物灌溉需水量;④确定作物不同阶段日耗水强度。根据该方法以新疆乌鲁木齐棉花为例,对此方法进行了详细的阐述,得到了新疆乌鲁木齐中等干旱年棉花各个生育阶段的日耗水强度,并建议按作物的不同生育阶段进行灌溉系统的运行管理。

Crop water requirement is the main basis for the planning, design, management and implementation of the irrigation and drainage project. How to evaluate the crop water requirement for a special area precisely is always a problem for the water conservan cy workers. In the work practice, crop water requirement is decided by the design crop water consumption, described in the micro-ir rigation engineering standards manual （GB/T 50485-2009）. However, the range of it in this manual is too wide and does not consid- er the values for the different places, different hydrologic year and different crop growing period. Since the crop water requirement calculated by this method is not precise and has big uncertainty, there will be some risks for the project running and management. In view of this, this paper presents the scientific method to compute the daily water consumption. The procedures are as follows： ①De ciding The typical year by ranking the frequency of historical rainfall; ②Calculating crop water requirement by the crop coefficient multiplying reference crop water consumption, which is obtained by the Penman-Monteith equation （FAO-1998）.③ Estimating the efficient rainfall in the study area and deciding the irrigation requirement. ④ Determining the crop daffy consumptive water for the different growing stage. This paper discussed the method detailedlv for the cotton croo in Urumchi. Xinjiang and obtained the daily consumptive water in the medium-drought year. The result suggests that the operation and management for irrigation system can be based on the water consumption at different crop growing stage.