Integrating remote sensing classification techniques for land use mapping in semi-arid regions: a case study of the Tamlouka basin, Algeria.

Worldwide, the majority of countries are actively devising strategies to address the challenges associated with unregulated and unmanageable development, the decline in environmental quality and the depletion of valuable agricultural land. This has led to a growing emphasis on understanding land use and land cover. In order to determine a better land use policy, legislators and planners need to know the current distribution of agricultural and urban lands, as well as information about changes in their proportions. Our approach combines data centred on main four themes-geology, slope gradient, hydrographic network and land use-in order to exploit classifier complementarities in our targeted agricultural study area of Tamlouka Basin, Algeria. Landsat 8 OLI-TIRs multispectral imagery and Shuttle Radar Topography Mission (SRTM-1arc v3) were used experimentally for classification and Digital Elevation Model (DEM) analysis. The classification's accuracy is confirmed by comparing the results of the decision tree classification with the validation samples. Results of the combination of several maps of classifications from the different methods show that the Tamlouka alluvial plain, having an area of 19,300 ha and an average slope gradient of less than 2°, drains the elevated reliefs that surround it via hydrographic network. The plain occupies 37% of the total basin area, with over of 60% being used for crop cultivation, regardless of fallow land areas in agricultural rotation at that time. The slope has been identified as a crucial factor determining land use patterns in the study area. This result can be used in prospective watershed management.

Hydrogeochemical processes controlling surface water quality for irrigation in a Mediterranean wetland ecosystem, Northeast Algeria.

Fetzara Lake, considered one of the most important wetlands in northeastern Algeria, was designated a Ramsar site in 2002. The waters in its watershed are affected by salinity, which influences their suitability for irrigation. To identify the factors influencing the quality of these surface waters, geochemical and statistical analyses were carried out on the basis of the results of chemical analyses of 51 samples collected, during two monitoring campaigns, from all the tributaries in the watershed. The findings show the dominance of three hydrochemical facies over the two campaigns: Na-Cl facies (55.17% and 22.73%) characterizes the waters water from Fetzara Lake outlet (drainage channel and wadi Meboudja), in relation to the influx of saliferous elements due to water evaporation in the lake. Ca-Mg-Cl (27.59% and 40.91%) and Ca-Mg-HCO3 (13.79%. and 13.79%) facies characterize the waters of the remaining tributaries, reflecting the dissolution of carbonate formations and the alteration of the Edough metamorphic basement. Multivariate statistical analysis, using principal component analysis (PCA), shows three water types: highly mineralized (EC > 3000 µS/cm), moderately mineralized (1000 < EC < 3000 µS/cm), and weakly mineralized (EC < 1000 µS/cm). Evaporation and silicate weathering are the main mechanisms controlling water mineralization according to the different bivariate plots. Furthermore, cation exchange indices (CAI-I and CAI-II) reveal that these reactions involve the adsorption of Na+ and K+ onto clay minerals, as well as the simultaneous release of Ca2+ and Mg2+ ions. Finally, the various quality indices (SAR, %Na, RSC and KR) revealed that the water in 36% of tributaries is unsuitable for irrigation. These findings will provide important information on surface water quality in the study area, particularly for irrigation purposes, and will contribute to the thoughtful and sustainable management of this resource.