Assessment of the Agricultural Intensification Impact on Groundwater Quality: a Case Study of the Triffa Plain

Since the modernisation of the agricultural sector in Morocco, the Triffa plain has been experiencing the development of techniques and increased production. However, agricultural intensification, the uncontrolled use of fertilisers and pesticides, and the succession of years of drought have contributed to the overexploitation of water resources and the degradation of the groundwater quality in the plain. To study the impact of the poor quality of groundwater (nitric pollution and salinisation) on the health of vegetation, we examined the spatiotemporal evolution of nitrates and salinisation in the plain, as well as the chlorophyll activity of crops (NDVI) using the Google Earth Engine (GEE) associated with MOD13Q1 version 6 images, for the years 2007-2009-2016-2022. The main results show an increase of 174% of the chlorophyll activity (NDVI ≥ 0.6) between 2007 and 2022, which make evidence of the significant intensification of the agricultural sector in the plain accompanied by a fast spread of nitric pollution regarding the groundwater. Hence, the area covered by the poor to very poor groundwater quality has almost doubled in a time interval of years (S2007Nmgl\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${S}_{2007}^{N\left(\frac{mg}{l}\right)}$$\end{document} = 235.5 km2, S2022Nmgl\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${S}_{2022}^{N\left(\frac{mg}{l}\right)}$$\end{document} = 408.65 km2). According to the analysis of the normalised difference vegetation index maps calculated for the study periods: 2007-2009-2016-2022 and the Pearson correlation matrix between the different variables, we conclude that the degradation of groundwater quality negatively affects the chlorophyll activity, which will consequently have an impact on the crop yield. The results prove the excessive use of fertilisers and pesticides, which led to increased chlorophyll activity associated with fast degradation of the water’s quality concerning nitrate concentrations.