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Abstract: This paper presents an overview of a decade (2002-2012) of studies performed on Soil-Plant-Atmosphere processes, in semi-arid areas (Haouz plain, Morocco). In this period, fifteen in-situ experiments on the dominant irrigated crops were performed, controlling the fluxes exchanged between land surface and atmosphere. The results showed that the physically based SVATs (ICARE, SiSPAT and ISBA) provided the best estimates of surface fluxes. For operational purposes, the FAO-56 approach and SAMIR Software (Satellite Monitoring for Irrigation) give a good estimate of evapotranspiration at field and regional scales, respectively. Finally, thermal infrared data were used in conjunction with SVATs to investigate the possibility of estimating the quantity of irrigation water. [Copyright &y& Elsevier]

Abstract: The objective of this study is to evaluate the capability of the two source energy budget (TSEB) to predict daily evapotranspiration over irrigated crops in a semi-arid area. The TSEB model presents particularly interesting skills for seasonal course of daily evapotranspiration regarding the limited number of inputs required with an RMSE of 0.75mm/day (33% on average) with regards to eddy-covariance measurements at least before crop senescence. By contrast, if focusing on a drying/wetting period surrounding a rain event, a lack of model reaction to stress is highlighted that could be a major drawback for irrigation scheduling. [Copyright &y& Elsevier]

Abstract: The monitoring of crop production and irrigation at a regional scale can be based on the use of ecosystem process models and remote sensing data. The former simulate the time courses of the main biophysical variables which affect crop photosynthesis and water consumption at a fine time step (hourly or daily); the latter allows to provide the spatial distribution of these variables over a region of interest at a time span from 10 days to a month. In this context, this study investigates the feasibility of using the normalised difference vegetation index (NDVI) derived from remote sensing data to provide indirect estimates of: (1) the leaf area index (LAI), which is a key-variable of many crop process models; and (2) crop coefficients, which represent the ratio of actual (AET) to reference (ET0) evapotranspiration. A first analysis is performed based on a dataset collected at field in an irrigated area of the Haouz plain (region of Marrakesh, Central Morocco) during the 2002–2003 agricultural season. The seasonal courses of NDVI, LAI, AET and ET0 have been compared, then crop coefficients have been calculated using a method that allows roughly to separate soil evaporation from plant transpiration. This allows to compute the crop basal coefficient (K cb) restricted to the plant transpiration process. Finally, three relationships have been established. The relationships between LAI and NDVI as well as between LAI and K cb were found both exponential, with associated errors of 30% and 15%, respectively. Because the NDVI saturates at high LAI values (>4), the use of remotely-sensed data results in poor accuracy of LAI estimates for well-developed canopies. However, this inaccuracy was not found critical for transpiration estimates since AET appears limited to ET0 for well-developed canopies. As a consequence, the relationship between NDVI and K cb was found linear and of good accuracy (15%). Based on these relationships, maps of LAI and transpiration requirements have been derived from two Landsat7-ETM+ images acquired at the beginning and the middle of the agricultural season. These maps show the space and time variability in crop development and water requirements over a 3km×3km irrigated area that surrounds the fields of study. They may give an indication on how the water should be distributed over the area of interest in order to improve the efficiency of irrigation. The availability, in the near future, of Earth Observation Systems designed to provide both high spatial resolution (10m) and frequent revisit (day) would make it feasible to set up such approaches for the operational monitoring of crop phenology and irrigation at a regional scale. [Copyright &y& Elsevier]

The main goal of this research was to evaluate the potential of the HYDRUS-1D numerical model for estimating the soil moisture (θ) at different depths, actual crop evapotranspiration (ETa) and its components (crop transpiration, Ta and soil evaporation, Ea) as well as the deep percolation (DP) of irrigated winter wheat under different water managements in the semi-arid region of Tensift-basin (central Morocco). The HYDRUS-1D simulations were performed at daily time step during the two growing seasons: 2002/2003 and 2015/2016. The model was firstly calibrated based on one field "denoted F1" data during the 2002/2003 cropping season by using the Levenberg-Marquardt method implemented in HYDRUS-1D model for optimizing various parameters of Van Genuchten equation that provide the minimum difference between measured and simulated soil moisture at four layers of soil (0–5, 5–10, 10–20, 20–30, 30–50 cm). Afterwards, the model validation was done based on the data from four fields of wheat: two fields "denoted F2 and F3" during the 2002/2003 and two other fields "denoted F4 and F5" during the 2015/2016 cropping season. All fields were irrigated with flooding system except the field F5 where drip irrigation was undertaken. In-situ measurements of θ was carried out using Time Domain Reflectometry (TDR) and gravimetric method ETa was measured by the Eddy Covariance system Ta and Ea were monitored using a lysimeter in F5 field. The results showed that the HYDRUS-1D model simulates the θ, ETa, Ta and Ea reasonably well. Additionally, the evaluation of the irrigation system on DP losses was investigated by comparing the simulation results over flood (F4) and drip (F5) irrigated fields. It was found that about 56% and 20% of seasonal supplied water were lost by DP in F4 and F5 sites, respectively. Such unexpected high amount of DP taking place in F5 field is due to the improper use of the drip irrigation system. • HYDRUS-1D model was calibrated for estimating water balance components (θ, ETa, Ta, Ea and DP) over irrigated winter wheat. • Compared to in-situ measurements, the HYDRUS-1D model simulates θ, ETa, Ta and Ea values reasonably well. • HYDRUS-1D model can be used to advise growers for improving irrigation management. [ABSTRACT FROM AUTHOR]