Detecting the response of irrigation water management to climate by remote sensing monitoring of evapotranspiration

El Ghandour, F.E.; Alfieri, S.M.; Houali, Youssef; Habib, Adnane; Akdim, Nadia; Labbassi, Kamal; Menenti, M.

doi:10.3390/w11102045

Detecting the response of irrigation water management to climate by remote sensing monitoring of evapotranspiration

Title

Detecting the response of irrigation water management to climate by remote sensing monitoring of evapotranspiration

Author

El Ghandour, F.E. (TU Delft Optical and Laser Remote Sensing; Chouaib Doukkali University)
Alfieri, S.M. (TU Delft Optical and Laser Remote Sensing)
Houali, Youssef (Chouaib Doukkali University)
Habib, Adnane (Chouaib Doukkali University; Chinese Academy of Sciences)
Akdim, Nadia (Chouaib Doukkali University)
Labbassi, Kamal (Chouaib Doukkali University)
Menenti, M. (TU Delft Optical and Laser Remote Sensing; Chinese Academy of Sciences)

Date

2019

Abstract

This study on a large irrigation scheme in Morocco addressed a two-fold question: (a) does the local water management authority adapt water releases to atmospheric water demand ET₀-P? and (b) does crop actual evapotranspiration respond to inter- and intra-annual variability in water releases? We have evaluated the inter-annual variability of ET₀-P during the period 1992-2017 and compared its anomalies (i.e., deviations from average) with anomalies in annual water release. Overall, it appeared that anomalies in water release were consistent with anomalies in ET₀-P. The actual evapotranspiration (ETa) was estimated using a time series of multi-spectral satellite image data by applying the Surface Energy Balance (SEBAL) algorithm in a dry, wet, and reference year. We have determined the quartiles of the distribution of the ET₀-P time series to identify these three years. The dry year was 2015-2016, the wet year was 2014-2015, and the reference (median of ET₀-P) was 2013-2014. Finally, we compared seasonal and annual anomalies in ET₀-P, ETa and release, W_d of irrigation water. In the period 1992-2017, the relative anomalies in ET₀-P and W_d were similar only in 2000-2001 and 2015-2016. The analysis of anomalies in water inflow and stocks confirmed the response in increased W_d following wet years with higher inflow and replenishment of the reservoir. The response of crop water use to the irrigation water supply was evaluated by comparing anomalies in the ratio of actual to maximum ET, i.e., ET_a/ET_c with anomalies in W_d. As regards the Sidi Bennour, Faregh, and Gharbia districts, the relative anomalies in ET_a/ET_c and W_d were consistent, i.e., they had the same sign and comparable magnitude. Overall, the study shows that water delivery W_d responds to inter-annual variability in the pre-irrigation season water inflows into the reservoirs, rather than in ET₀-P. On the other hand, actual crop water use, i.e., ET_a/ET_c, does respond to inter- and intra-annual variability in W_d. This evidence suggests that there is scope for adaptive water management based on a flexible adaptation of water release to inter- and intra-annual variability in water demand.