A Diachronic Analysis of the Vegetation Cover in a Spate Irrigation Perimeter – Case Study: The El Feidh Region, Biskra, Algeria

This article aims to study a model of traditional agriculture using spate irrigation. To this end, we relied on a methodological approach based on the calculation of spectral indices: Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Bare soil Index (BI), and Salinity Index (SI), which allowed us to evaluate the diachronic changes in the soil surface condition in the study area, particularly the evolution of the vegetation cover. The processing of multi-date Landsat images [1985–2020] revealed a widespread degradation in the vegetation cover at the El Feidh perimeter, as well as an increase in salinity. The results obtained indicate that in 1985, the average of the vegetation index (NDVI) was 0.49, which is very important compared to the years 2000 and 2020, when the average NDVI was 0.20 and 0.12, respectively. The vegetation cover area decreased from 98.89% in 1985 to 97.72% in 2000, only to drop again to 42.98% in 2020. In contrast, the average salinity index has increased over the years: it was lower in 1985 (SI = 952.04) than in 2020 (SI = 2261.63). Furthermore, the diachronic analysis of the NDWI shows that soil and plant moisture have also decreased significantly: the average NDWI was 0.19 in 1985, then dropped to -0.03 in 2000, only to drop again to -0.08 in 2020.