MOP 70是根据蒸发和蒸散物理（ET）估算作物灌溉项目所需水量的综合参考。由环境和水资源研究所灌溉和排水委员会灌溉和水文学蒸散委员会赞助，该委员会是一个综合性参考，用于根据蒸发和蒸散物理（ET）估算作物灌溉所需水量。新版MOP 70更新和扩展了1990年的原始版本，提供了改进和标准化的方法来估算蒸发和ET，并应用和评估计算。 这些方法既有物理基础，又有实践基础，提高了系统设计和管理的清晰度、准确性和一致性。它们在涉及水协议、水纠纷和水权的法律应用中也很有用。随着水资源竞争的加剧和水资源的枯竭，本书提供了准确量化灌溉农业消耗水量的关键工具。第一部分包括基本概念和物理原理，如蒸发和ET过程、土壤-水-植物系统、能量平衡、表面能-气团相互作用和水面蒸发。关于陆地表面ET的第二部分解释了测量的组成部分和估算的细节； 参考作物ET；土壤蒸发；作物系数法；Penman-Monteith方程和能量平衡方程；以及区域估计。第三部分讨论了灌溉需水量（IWR）和径流消耗的估算。13个附录提供了平均和基本作物系数表，以及手册中使用的概念和方程式的背景信息。MOP 70适用于研究水问题的咨询工程师和科学家，以及农业和土木工程、水文学、环境和农业科学的讲师。

MOP 70 is a comprehensive reference to estimating the water quantities needed for irrigation of crops projects based upon the physics of evaporation and evapotranspiration (ET).Sponsored by the Committee on Evapotranspiration in Irrigation and Hydrology of the Irrigation and Drainage Council of the Environmental and Water Resources Institute of ASCEEvaporation, Evapotranspiration, and Irrigation Requirements is a comprehensive reference to estimating the water quantities needed for irrigation of crops based upon the physics of evaporation and evapotranspiration (ET). This new edition of MOP 70, which updates and expands the 1990 original, provides improved and standardized methods to estimate evaporation and ET and to apply and evaluate calculations. The methods, which have both a physical and practical basis, improve clarity, accuracy, and consistency for systems design and management. They are also useful in legal applications involving water agreements, water disputes, and water rights.As competition for water increases and water resources are depleted, this book provides the critical tools to accurately quantify amounts of water consumed by irrigated agriculture. The first part covers basic concepts and physical principles, such as evaporation and ET processes, soil-water-plant systems, energy balance, surface energy-air mass interactions, and evaporation from water surfaces. The second part on ET from land surfaces explains components of measurement and details on estimation; reference crop ET; evaporation from soil; the crop coefficient method; the Penman-Monteith and energy-balance equations; and regional estimates. A third part discusses estimation of irrigation water requirements (IWR) and streamflow depletions. Thirteen appendixes provide tables of mean and basal crop coefficients and background information on concepts and equations used throughout the manual.MOP 70 is intended for use by consulting engineers and scientists working on water issues and by instructors of agricultural and civil engineering, hydrology, and environmental and agricultural sciences.