In the Hetao Irrigation Districts of the Ningxia autonomous region, Upper Yellow River Basin, the "con-tinuous deep flooding irrigation" method is used for the rice paddies. The field irrigation water use during the rice-growing season is two to three times higher than in other regions of North China where water-saving practices have been introduced. This paper, based on the data measured in experimental rice fields and sub-branch canal systems, presents main results concerning crop evapotranspira-tion, percolation and irrigation requirements for deep and shallow water irrigation. Causes for water waste relate to both the lack of regulation in supply and distribution canals and to the poor management of paddy fields. The potential for water saving is discussed using water bal-ance data. Improved irrigation techniques and water man-agement strategies, including the shallow water irrigation method, are suggested considering the expected impacts and benefits. Replacing the current continuous deep flood-ing with the shallow-ponded water irrigation method may reduce the growing season irrigation water use from 1,405 to 820mm in average, with a likely increase in yields of 450kg/ha. Water productivity would then increase from 0.49 to 1.03kg/m3. Adopting improved canal manage-ment and modernization of regulation and control struc-tures may lead to decreasing the gross irrigation demand from the present 3,100mm to about 1,280mm, which would highly benefit the environmental conditions in the area.

In the southern part of China over 70% of the cultivated area is under rice. A tremendous amount of water is used for the rice fields under the traditional irrigation method, termed 'shallow flooding irrigation1. Since the 1980s, in some provinces in south China, a new irrigation technique for rice, termed 'water-saving irrigation', has been advanced. In recent years this new technique has become widespread. The basic feature of this new irrigation technique is that there is no water layer above the soil surface in rice fields during the growing season of rice after the stage of recovering. This technique not only saves water and increases the rice yields, it also: reduces soil and water pollution; improves soil aeration; improves the field's microclimatic condition; reduces rice diseases and insect pests; and improves the regional water balance. This paper discusses the details of the water-saving irrigation technique for rice, and its potential environmental impact in south China.

A network of about 30 basic and more than 150 ordinary irrigation experiment stations for observing the evopatransptration of rice the soutern and middle parss of China has been formed. In this paper, based on the analysis of the observation data from the majority of the besic and a port of the ordinary stations, the patterns of vanation of evaputran-sptrotian of rice in space and time are expounded. Based on the inference, calcutation. and verification by the observation data from the above stations, the main method for cal-culating the evapotransptration of rice in China are exponded and recommended. In par-ticular, three new methods are introduced and discussed Finally. the method and results of making the isoline maps of evapotranspiration of rice in China are introduced.

The forecast of cropevapotranspiration (ET) is one of the essential parts of the work for compiling e dynamic plan of imigation water use. It plays an important role in saving water, ineressing ropyields and economic benefits in en imigation area. In this paper, amocile for a shortrange glass than 15 days forocasl of ET is introduced and ciscussoid The ralationship between ET ard the melecrological factors and ono-motoorological tactors such as tho factors of plant and scil are enalysed. The models which express the effects of meteorology. Plant and soil on ET separately are recommended, Based on these moreis a combined model for the forecast of ET and the eonerete methods of the short-range forecast of ET are presented.

本文根据作者在全国协作研究作物需水量等值线图（湖北协作组）工作中取得的成果及经验，并暧取兄弟省、市、自治区及国外经验，就作物需水量等值线图的类别、绘制原理和方法以及应甩等方面进行论述。从满足生产需要出发，提出绘制四种等值线圈：（1）垒年各月的日平均参照作物需水量等值线图；（2）作物生育期内各月的日平均作物稚水量等值线图；（3）作物全生育期需水量等值线图，（4）作物全生育期日平均需水量等值线图。阐述了每种图的依据、作用及绘制方法。推荐用“改进的彭曼法”及“作物系数”计算作物需水量；指出应用此法时在推算净辐射及空气动力学项中常产生的错误，分析错误的原因，提出正确的算法。最后，阐述应用需水量等值线图绘制净灌溉定额等值线图的方法，以便用该图进行灌溉区划和灌溉工程的规划、设计与管理；用实例说明利用需水量等值线图综合分析需水量在空间和时间两方面的变化规律，藉以指导抗旱和调整农业布局。

21世纪初学者期，我国将以空前的规模发展节水灌溉事业，计划安排大量的全国性节水灌溉项目。为了合理、高效地开展这些项目的规划、设计、建设与运行管理工作，使其节水效果好、经济效益高。提出了应注意以下五方面原则性的技术问题：节水灌溉的涵叉与目的、技术措施体系、尺度效应、效果评估指标体系、主攻方向。文中对这些问题进行了具体论述。

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、县、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，井提出了新的计算土壤分修正系数的数学模型。

水稻是中国最主要的粮食作物之一。其产量约占粮食作物总产量的40%；在全国约1.1×10∧8hm2的粮食作物总面积中。稻田面积约占28%。20世纪80年代以来。水稻产区的水资源短缺已成为当地农业生产中的重要问题，各地试验、开发、应用与推广了许多种水稻节水灌溉模式。文章根据这些新的水稻灌溉模式试验结果与推广经验，将我国水稻节水灌溉主要模式归纳为浅、湿、晒结合，闻歇淹水，半旱栽培和蓄雨型等4类、阐述了这些模式的田问水分控制标准以及节水、增产和提高水分生产率的潜力；提出了该4类模式的选择原则以及应用这些模式时应注意的问题；分析、讨论了推广这些模式能够持续节水与提高水分生产率的机理以及对环境的影响。

Based on the analysis of the experimental data, the models of water-production function (WPF) for rice, which can be applied to both northern and southern parts of China, are investigated The regularity ofthe variation of water sensitivity parameters in various models has been discussed It is suggested that Jensen model is the applicable model of WPF for rice in China The regularity of the variation of water sensitivity index λ. in Jensen model with the hydrology yeats and regions, especially, the relationship between. λ and the reference evapotranspiration ETO has been presented Thus. the principle and methods for widening the ranges of time and space for applying WPF of rice have been established.

本文根据广西桂林地区灌溉试验中心站1988年以来的五年观测试验成果。分析研究适用于我国南方的水稻水分生产函数模型。探讨各种模型中水分敏感性参数的变化规律，提出水稻水分生产函数随水文年度呈规律性变化的观点，特别是具体提出了Jensen模型中水分敏感指数与参照作物需水量的关系。为拓宽水分生产函数应用的时空范围提依据及方法。