Analyzing satellite data time-series for agricultural expansion and its water consumption in arid region: a case study of the Farafra oasis in Egypt's Western Desert

Abstract

The harsh climate, prevalent soil properties, and a lack of water in the desert environment make controlling the vegetation cover challenging. The effects of changes in vegetation cover on evapotranspiration in the Farafra region of Egypt were investigated using satellite data time-series analysis. The collected time-series satellite data from 2000 to 2020 of Landsat 5 (TM) and Landsat 8 (OLI/TIRS) were analyzed by the Google Earth Engine (GEE) platform. The most significant element of this article is a long-term comprehensive satellite data analysis using cloud computing to determine soil, vegetation, and local climate interactions. Based on an analysis of the normalized difference vegetation index (NDVI) and actual evapotranspiration (ETa), agricultural expansion and water consumption have been calculated. Agricultural expansion has increased by 102%, from 3340 ha to 6774 ha, at an average of + 163.5 ha/year over the last 21 years. As a result, agricultural water consumption increased by 587%, from 1.88 to 12.97 Mm3, or + 0.53 Mm3/year. Agricultural density has increased, leading to a 20.3% increase in maximum NDVI. With R2 = 0.91, the correlation analysis revealed a strong and positive relationship between annual NDVI and water consumption, implying that vegetation cover lowers the surface temperature and increases water consumption. The environment-enhancing effects of agricultural expansion on the local climate were apparent, as the brightness temperature (Tb) indicated a 7.6% decrease in surface temperature, at an average of −0.11 °C/year, while the air temperature decreased by 2.8%, at an average of −0.03 °C/year.