实时灌溉预报是制定动态灌溉用水计划的基础，对灌区节水，增加作物产量和提高经济效益起着重要作用。其重点与难点内容是作物需水量实时预报。国内外已有的作物需水量预报方法与模型，是建立在历史典型水文年资料基础之上的，无法用于实时预报。文章分析了作物需水量与气象条件和非气象条件（主要是植物条件以及土壤条件）之间的关系，提出了根据天气类型、作物绿叶覆盖率和土壤有效含水率3项因素进行作物需水量实时预报的方法与模型，介绍了具体的预报步骤与计算框图，改进了常规的预报方法，主要是用预报的天气类型（晴、昙、阴、雨）代替修正彭曼法中所需的气温、空气湿度、日照时数与风速4项气象因素，用绿叶覆盖率代替叶面积指数，并提出了新的计算土壤水分修正系数的数学模型。

The real-time forecast of irrigation is one of the essential part of the work for compiling a dynamic plan of irrigation water use. It plays an important role in saving water, increasing crop yields and economic benefits in an irrigation area. The real-time forecast of water requirements of crops is the essential and difficult part in the real-time foreast of irrigation. The methods and models for the conventional forecast of crop water requirement ,applied both in China and the world, are based on the application of the historic data from typical hydro-logic years. They can not used for the real-time forecast. In this paper, on the basis of the analyses of the relationship between the crop water requirements and the meteorological factors and non-meteorological factors such as the factors of plant and soil, the method and models for the real-time forecast of crop water requirements based on the factors of weather types, leaves cover percentage and effective soil moisture are presented and recommended. The concrete steps and computer block diagram are introduced. The main improvements are that the weather type is used instead of such four meteorological factors in Modified Peman's Eguation as air temperature, humidity, sunshine hour and wind speed,the leaves cover percentage is used instead of the leaves area index, and an improved equation for calculating soil moisture correction coefficient is proposed. Based on the results of the real-time forecast of crop water requirement and precipitation, the real-time measurement of soil moisture (for dry food crops fields) or depth of water layer (for paddy fields) and the maximum and minimum values of soil moisture content or water depth for getting high yields and saving water, and the calculation of field water balance, the method and models of real-time irrigation forecast including the real-time forecast of the date and quota of irrigation for both dry food crops fields and paddy fields are presented. In this paper, the precision of the real-time forecast and its effects on increasing yield and saving water are also introduced and discussed.