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See detailUsing remote sensing (optical and radar) and modeling to support the irrigation management of cereals in a semi-arid region: a case study of the Tadla irrigated perimeter in Morocco
Benabdelouahab, Tarik ULiege

Doctoral thesis (2015)

Summary Irrigated agriculture is an important strategic sector in Morocco, it accounts for about 45%, on average, of the agricultural Gross Domestic Product, contributing thus to food security and ... [more ▼]

Summary Irrigated agriculture is an important strategic sector in Morocco, it accounts for about 45%, on average, of the agricultural Gross Domestic Product, contributing thus to food security and employment. It occupies 15% (about 1.5 million ha) of the total cultivated area in the country. Irrigation scheme managers need to ensure that water is optimally used in the irrigated perimeters and that water shortages are avoided. For large areas under irrigation, this can be achieved through water monitoring at plot level using modeling and satellite-based methodologies. The main objective of this research was to assess the use of optical and radar remote sensing and of crop modeling in the irrigation monitoring and management of wheat in the irrigated perimeter of Tadla. The potential of spectral indices derived from SPOT-5 images was explored for comparing, quantifying and mapping surface water content changes at regional and local levels. Indices were computed using the reflectance in red, near infrared and shortwave infrared bands. Our findings show that the normalized difference water index (NDWIRog) could be used to estimate and map the surface water content of wheat plots, from bare soil to fully covered soil. Backscatter threshold values derived from SAR images were used to detect irrigation water supplies in wheat plots and the optimal acquisition frequency of SAR images was determined in order to ensure continuous monitoring. A field crop model (AquaCrop) was adjusted to simulate durum wheat yields and the temporal evolution of soil moisture status in order to manage and schedule irrigation water supplies and assess their impact on yield. Currently, the approaches described in this paper are being applied independently. This research was intended, therefore, to provide tools to help policy-makers and stakeholders improve irrigation monitoring and mitigate wheat water stress at the field and irrigation perimeter levels in semi-arid areas. Keywords: irrigation management, spectral index, wheat, backscattering, SAR, semi-arid, Morocco. [less ▲]

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See detailMonitoring surface water content using visible and short-wave infrared SPOT-5 data of wheat plots in irrigated semi-arid regions
Benabdelouahab, Tarik ULiege; Balaghi, Riad ULiege; Hadria, Rachid et al

in International Journal of Remote Sensing (2015), 36(15), 4018-4036

Irrigated agriculture is an important strategic sector in arid and semi-arid regions. Given the large spatial coverage of irrigated areas, operational tools based on satellite remote sensing can ... [more ▼]

Irrigated agriculture is an important strategic sector in arid and semi-arid regions. Given the large spatial coverage of irrigated areas, operational tools based on satellite remote sensing can contribute to their optimal management. The aim of this study was to evaluate the potential of two spectral indices, calculated from SPOT-5 high-resolution visible (HRV) data, to retrieve the surface water content values (from bare soil to completely covered soil) over wheat fields and detect irrigation supplies in an irrigated area. These indices are the normalized difference water index (NDWI) and the moisture stress index (MSI), covering the main growth stages of wheat. These indices were compared to corresponding in situ measurements of soil moisture and vegetation water content in 30 wheat fields in an irrigated area of Morocco, during the 2012–2013 and 2013–2014 cropping seasons. NDWI and MSI were highly correlated with in situ measurements at both the beginning of the growing season (sowing) and at full vegetation cover (grain filling). From sowing to grain filling, the best correlation (R2 = 0.86; p < 0.01) was found for the relationship between NDWI values and observed soil moisture values. These results were validated using a k-fold cross-validation methodology; they indicated that NDWI can be used to estimate and map surface water content changes at the main crop growth stages (from sowing to grain filling). NDWI is an operative index for monitoring irrigation, such as detecting irrigation supplies and mitigating wheat water stress at field and regional levels in semi-arid areas. [less ▲]

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See detailMapping of vegetation water content using Shortwave Infrared SPOT5 data to monitor irrigation in semi-arid regions.
Benabdelouahab, Tarik ULiege; Balaghi, Riad ULiege; Lionboui, Hayat et al

Conference (2014, May 28)

Half of world’s food comes from irrigated area that uses about 72% of available water resources. In Morocco, water availability is the main limiting factor for crop growth and final yield and it is ... [more ▼]

Half of world’s food comes from irrigated area that uses about 72% of available water resources. In Morocco, water availability is the main limiting factor for crop growth and final yield and it is becoming a national priority for the agricultural sector. This situation leads the stakeholders to define most favorable strategies in planning and management of available water resources, on one hand, and to assess accurately vegetation water content status, on the other hand, in order to improve irrigation scheduling and prevent water stress adversely affecting yield. Remotely sensed reflectance has been used to estimate vegetation water content for different crops and to monitor water irrigation per surface unit, considering its high temporal and spatial resolution. In this study, we used two spectral indices of vegetation water content indicator (the Normalized Difference Infrared Index (NDII) and the Moisture Stress Index (MSI)) developed using Near Infrared (NIR) and Short Wave Infra-Red (SWIR) bands. The study area is the irrigated perimeter of Tadla in Morocco (35% dominated by irrigated wheat crop). In a first step, we compared observed vegetation water content of 16 studied plots of wheat and derived spectral indices NDII and MSI at the end of cropping season. The two images used at this step were acquired on March 26, 2013 and on April 11, 2013 when soil was fully covered by vegetation. Statistical analyses showed that the two spectral indices, NDII and MSI, simulated accurately vegetation water content. The statistical indicators, r, R², RMSE, nRMSE and MAE were -0.81, 0.65, 3.26% of water content (≈0.13 kg/m²), 4.26% and 2.69% for the NDII and 0.81, 0.65, 3.27% of water content (≈0.14 kg/m²), 4.27% and 2.72% for the MSI, respectively. To validate these results, we compared observed vegetation water content values and those predicted using the k-fold CV method. The errors were minimal for NDII and MSI, and the indicators of model evaluation obtained for predicted vegetation water content from NDII were: RMSE = 3.17%, nRMSE = 4.13%, MAE = 2.52% and R²=0.64. For MSI, these indicator were RMSE = 3.28%, nRMSE = 4.29%, MAE = 2.68% and R²=0.61. In a second step, we delimited the cereal area in the studied perimeter using a supervised classification method. The classification has been validated and the overall accuracy and Kappa coefficient were estimated respectively at 96.7% and 0.9545. Based on the regression model resulting from the comparison between NDII and measured vegetation water content, we produced maps of vegetation water content of wheat over the whole Beni-Moussa East irrigated area (41,000 hectares). The results of this work demonstrated the potential of spectral indices (NDII and MSI) derived from SPOT5 satellite images data to quantify and map vegetation water content of wheat. It showed also the potential of the SWIR band to improve the monitoring of irrigation by mapping water stress of wheat at field and regional level. [less ▲]

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See detailApplication de la télédétection optique et RADAR pour contribuer à une gestion hydrique efficiente de la céréaliculture des périmètres irrigués au Maroc : Cas du périmètre irrigué du Tadla.
Benabdelouahab, Tarik ULiege; Balaghi, Riad ULiege; Barbier, Christian ULiege et al

Scientific conference (2013, February 06)

« l’Application de la télédétection optique et radar pour contribuer à la gestion de la céréaliculture dans les périmètres irrigués : cas du périmètre irrigué de Tadla ». Cette présentation est un résumé ... [more ▼]

« l’Application de la télédétection optique et radar pour contribuer à la gestion de la céréaliculture dans les périmètres irrigués : cas du périmètre irrigué de Tadla ». Cette présentation est un résumé de projet de thèse doctorale qui vise à contribuer à une gestion synoptique du périmètre irrigué grâce aux outils de la télédétection spatiale optique et radar combinés à la modélisation agrométéorologique. [less ▲]

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