Sensing and control of crop water status

In arid and semi-arid regions, irrigation management is important to avoid water loss by soil evaporation and deep percolation (DP). In this context, estimating the irrigation water demand has been investigated by many studies in the Haouz plain. However, DP losses beneath irrigated areas in the plain have not been quantified. To fill the gap, this study evaluated DP over two drip-irrigated citrus orchards (Agafay and Saada) using both water balance and direct fluxmeter measurement methods, and explored the simple FAO-56 approach to optimise irrigation in order to both avoid crop water stress and reduce DP losses in case of non-saline and saline soils. The experimental measurements determined different terms of the water balance by using an Eddy-Covariance system, fluxmeter, soil moisture sensors and a meteorological station. Using the water balance equation and fluxmeter measurements, results showed that about 37% and 45% of supplied water was lost by DP in Saada and Agafay sites, respectively. The main cause of DP losses was the mismatch between irrigation and the real crop water requirement. For Agafay site, it was found that increased over-irrigation had the effect of reducing soil salinity by leaching salts. The applied FAO-56 model suggested an optimal irrigation scheduling by taking into account both rainfall and soil salinity. The recommended irrigations could save about 39% of supplied water in non-saline soil at Saada and from 30% to 47% in saline soil at Agafay

Estimation of soil evaporation and infiltration losses using stables isotopes, fluxmeter and eddy-covariance system for citrus orchards in a semi-arid region (Morocco)

In arid and semi-arid regions water scarcity is one of the main limiting factors for economic growth. In the context, an experimental setup was conceived to monitor seasonal water consumption of citrus plant irrigated by drip irrigation system in Agafay station, middle of Morocco. For that, an Eddy-Covariance system, meteorological station, fluxmeter, as well as measurements of soil moisture and temperature were continuously operated during experimentation. The stable isotope was used to partition Evapotranspiration (ET) components. By using the water balance equation, the results showed that about 37% of total irrigation and rainfall is lost by infiltration and runoff. Additionally, the partitioning of evapotranspiration using the stable isotope showed that soil evaporation is very small compared to the transpiration at least during tow sampling days. This result confirms that the irrigation method applied by the farmer was very appropriate for the orchard but it is necessary to re-examine amount of water applied and timing of irrigation in order to minimise the loss by infiltratio

An integrated modelling and remote sensing approach for hydrological study in arid and semi-arid regions : the SUDMED programme

Recent efforts have been concentrated in the development of models to understand and predict the impact of environmental changes on hydrological cycle and water resources in arid and semi-arid regions. In this context, remote sensing data have been widely used to initialize, to force, or to control the simulations of these models. However, for several reasons, including the difficulty in establishing relationships between observational and model variables, the potential offered by satellite data has not been fully used. As a matter of fact, a few hydrological studies that use remote sensing data emanating from different sources (sensors, platforms) have been performed. In this context, the SUDMED programme has been designed in 2002 to address the issue of improving our understanding about the hydrological functioning of the Tensift basin, which is a semi-arid basin situated in central Morocco. The first goal is model development and/or refinement, for investigating the hydrological responses to future scenario about climate change and human pressure. The second aim is the effective use of remote sensing observations in conjunction with process models, to provide operational prognostics for improving water-resource management. The objective of this paper is to present the SUDMED programme, its objectives, and its thrust areas, and to provide an overview of the results obtained in the first phase of the programme (2002-2006). Finally, the lessons learned, future objectives, and unsolved issues are presented

Remote Sensing of Water Resources in Semi-Arid Mediterranean Areas : the joint international laboratory TREMA

Monitoring of water resources and a better understanding of the eco-hydrological processes governing their dynamics are necessary to anticipate and develop measures to adapt to climate and water-use changes. Focusing on this aim, a research project carried out within the framework of French-Moroccan cooperation demonstrated how remote sensing can help improve the monitoring and modelling of water resources in semi-arid Mediterranean regions. The study area is the Tensift Basin located near Marrakech (Morocco) - a typical Southern Mediterranean catchment with water production in the mountains and downstream consumption mainly driven by agriculture. Following a description of the institutional context and the experimental network, the main recent research results are presented: (1) methodological development for the retrieval of key components of the water cycle in a snow-covered area from remote-sensing imagery (disaggregated soil moisture from soil moisture and ocean salinity) at the kilometre scale, based on the Moderate Resolution Imaging Spectroradiometer (MODIS); (2) the use of remote-sensing products together with land-surface modelling for the monitoring of evapotranspiration; and (3) phenomenological modelling based only on time series of remote-sensing data with application to forecasting of cereal yields. Finally, the issue of transfer of research results is also addressed through two remote sensing-based tools developed together with the project partners involved in water management and irrigation planning