Use of Digitalized Hydrogeological Maps for Evaluation of Salt-Affected Soils of Large Areas

Abstract

Soil salinity and sodicity is often related to the presence of shallow groundwater. We evaluated the importance of factors that affect soil salinity and sodicity in one typical salt-affected area, the Carpathian Basin. Five hydrogeological maps were used to demonstrate the occurrence of salt-affected soils in the Great Hungarian Plain. The 1:500,000 scale maps showed the depth to groundwater, the concentration of soluble salts in the groundwater, the height of groundwater table above sea level, textural classes of near-surface formations, and the dominant ions in the groundwater. After digitizing the maps, a database was created, and the association between variables was quantified by the uncertainty coefficient. The largest statistical association with the occurrence of salt-affected soils was found for the height of groundwater above sea level, the dominant ions of groundwater, and the textural class of subsurface layers. The hydrogeological maps showed close interrelationships of these factors, therefore no single factor, but a combination of factors, were responsible for the occurrence of salt-affected soil types. Regarding the most frequent categories of hydrogeological variables in which the salt-affected soils occurred, two groups were distinguished: the noncalcareous solonetzes and related soils (26.7% of the Plain) were most frequently associated with clay and the groundwater is dominated by Na + and HCO 3 - with a height above sea level at 80-90 m. The sodic solonchak and calcareous meadow solonetzes cover only 1.5% of the Plain, and these are most frequently associated with sand, where Ca 2+ and HCO 3 - was dominant in the groundwater. However this group did not adhere to one specific zone of groundwater level, and also showed territorial segregation.