Contributions of groundwater conditions to soil and water salinization

Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or human-induced processes. Wat er is lost through one or any combination of four main mechanisms: evaporat ion, evapotranspiration, hydrolysis. and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition. These models are in a greement with the weathering and depositional geological processes that hav e formed soils and overburden in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In all represented cases, groundwater is the main geological agent for tra nsmitting, accumulating, and discharging salt. At a small catchment scale i n South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally d ischarges in lakes, where most of the saline groundwater is concentrated. I n the hummocky terrains of the Northern Great Plains Region, Canada and USA , the localized recharge and discharge scenarios cause salinization to occu r mainly in depressions, in conjunction with the formation of saline soils and seepages. On a regional scale within closed basins, this process can cr eate playas or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path and forms a s aline zone at the distal end. The saline zone in each rift forms a closed r idge, which coincides with the closed trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline- earth carbonate precipitation and dissolution of capillary salts.