CARTOGRAPHY AND DIACHRONIC STUDY OF THE NAAMA SABKHA (SOUTHWESTERN ALGERIA) THROUGH NDVI, NDWI INDICES, SALINITY, ELECTRICAL CONDUCTIVITY AND SOIL pH
Published 2019-01-01
Keywords
- Sabkha, Cartography,Naama, Biodiversity, Salinity, NDVI, NDWI, Diachronic, Algeria, Vegetation, Climate change,
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Abstract
The present work focuses on the past (1985) and current (2018) status of the Naama’s Sabkha, particularly its salinity, vegetation and water status. The acquired results will be useful for the preservation of Sabkha biodiversity. The representative sampling allowed us to
make 136 soil samples over two depths (4 cm and 30 cm). The salinity analyses showed that the maximum values are of the order of 115.3 g/l at 4 cm and 80.3 g/l at of 30 cm depth. Regarding to the soil conductivity, the highest values recorded at 4 cm and 30 cm are
respectively 198.4 mS.cm-1 and 141.89 mS.cm-1. At the same time, the results highlight that the Sabkha soil is weakly alkaline with strongly alkaline. The diachronic study based on the NDVI (Normalized Difference Vegetation Index) analysis of the Landsat_5, Landsat_8 and Sentinel_2 satellite images showed the installation of a varied vegetation during 33 years.
The use of NDWI (Normalized Difference Water Index) for the period (1985 to 2018) highlights the importance of the water deficit in the region. The results of the images geostatistical treatments shed light on the changes that have occurred in particular the increase in the area of Sabkha, which was 431 Ha in 1985 to 514 Ha in 2018. This is an increase of 83 Ha for 33 years. In other words, an evolution of 19.25% compared to the area of 1985.