California Simulation of Evapotranspiration of Applied Water and Agricultural Energy Use in California

Morteza N Orang; Richard L Snyder; Shu Geng; Quinn J Hart; Sara Sarreshteh; Matthias Falk; Dylan Beaudette; Scott Hayes; Simon Eching

摘要

The California Simulation of Evapotranspiration of Applied Water (Cal-SIMETAW) model is a new tool developed by the California Department of Water Resources and the University of California, Davis to perform daily soil water balance and determine crop evapotranspiration (ETc), evapotranspiration of applied water (ETaw), and applied water (AW) for use in California water resources planning. ETaw is a seasonal estimate of the water needed to irrigate a crop assuming 100%irrigation efficiency. The model accounts for soils, crop coefficients, rooting depths, seepage, etc. that influence crop water balance. It provides spatial soil and climate information and it uses historical crop and land-use category information to provide seasonal water balance estimates by combinations of detailed analysis unit and county (DAU/County) over California. The result is a large data base of ETc and ETaw that will be used to update information in the new California Water Plan (CWP). The application uses the daily climate data, i.e., maximum (Tx) and minimum (Tn) temperature and precipitation (Pcp), which were derived from monthly USDA-NRCS PRISM data (PRISM Group 2011) and daily US National Climate Data Center (NCDC) climate station data to cover California on a 4 km×4 km change grid spacing. The application uses daily weather data to determine reference evapotranspiration (ETo), using the Hargreaves-Samani (HS) equation (Hargreaves and Samani 1982, 1985). Because the HS equation is based on temperature only, ETo from the HS equation were compared with CIMIS ETo at the same locations using available CIMIS data to determine correction factors to estimate CIMIS ETo from the HS ETo to account for spatial climate differences. Cal-SIMETAW also employs near real-time reference evapotranspiration (ETo) information from Spatial CIMIS, which is a model that combines weather station data and remote sensing to provide a grid of ETo information. A second database containing the available soil water holding capacity and soil depth information for all of California was also developed from the USDA-NRCS SSURGO database. The Cal-SIMETAW program also has the ability to generate daily weather data from monthly mean values for use in studying climate change scenarios and their possible impacts on water demand in the state. The key objective of this project is to improve the accuracy of water use estimates for the California Water Plan (CWP), which provides a comprehensive report on water supply, demand, and management in California. In this paper, we will discuss the model and how it determines ETaw for use in water resources planning.

机译：加州水应用蒸散模拟（Cal-SIMETAW）模型是由加利福尼亚州水利部和加州大学戴维斯分校开发的新工具，用于执行每日土壤水分平衡并确定作物的蒸散量（ETc），应用水的蒸散量。水（ETaw）和应用水（AW）用于加利福尼亚州的水资源规划。 ETaw是假设灌溉效率为100％时灌溉作物所需水量的季节性估算值。该模型考虑了影响作物水分平衡的土壤，作物系数，生根深度，渗流等。它提供空间土壤和气候信息，并使用历史作物和土地利用类别信息通过详细分析单位和县（DAU /县）的组合来提供季节性水平衡估算。结果是建立了大型的ETc和ETaw数据库，这些数据库将用于更新新的加利福尼亚水计划（CWP）中的信息。该应用程序使用每日气候数据，即最高（Tx）和最低（Tn）温度和降水（Pcp），这些数据是根据USDA-NRCS每月PRISM数据（PRISM Group 2011）和美国国家气候数据中心（NCDC）得出的）气候站数据覆盖了4 km×4 km变化的网格间距上的加利福尼亚。该应用程序使用Hargreaves-Samani（HS）方程（Hargreaves和Samani 1982，1985）使用每日天气数据来确定参考蒸散量（ETo）。由于HS方程仅基于温度，因此使用可用的CIMIS数据将HS方程中的ETo与CIMIS ETo在相同位置进行比较，以确定校正因子，以估算HS ETo的CIMIS ETo，以解决空间气候差异。 Cal-SIMETAW还采用了来自空间CIMIS的近实时参考蒸散量（ETo）信息，该模型是结合气象站数据和遥感以提供ETo信息网格的模型。还从USDA-NRCS SSURGO数据库建立了第二个数据库，其中包含整个加利福尼亚州的可用土壤持水量和土壤深度信息。 Cal-SIMETAW程序还具有从月平均值生成每日天气数据的能力，可用于研究气候变化情景及其对该州需水量的可能影响。该项目的主要目标是提高加利福尼亚水计划（CWP）用水估算的准确性，该计划提供了有关加利福尼亚水供应，需求和管理的综合报告。在本文中，我们将讨论该模型及其如何确定用于水资源规划的ETaw。

California Simulation of Evapotranspiration of Applied Water and Agricultural Energy Use in California

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