Applications of geographic information systems in studying changes in groundwater quality and soil salinity in Sohag Governorate

摘要

Sohag governorate is a narrow long strip of a cultivated valley located in upper Egypt. Groundwater and soil samples were collected along the Nile river, starting form the southern border to the northern border of Sohag governorate to assess the groundwater quality and soil salinity between 1991 and 2006. The obtained data reveal that the electrical conductivity of well waters (ECw) was classified to four classes (250-750, 750-2250, 2250-5000 and greater than 5000 μS/cm). The results showed an increase in the groundwater salinity within 15 years, especially in the first class where it increased from 9% in 1991 to 14% in 2006 but it raised from 17% in 1991 to 37% in 2006 for the third class. The surface and subsurface soil layers showed an increase trend in the soil salinity from 1991 to 2006. The soil salinity increased with depth from 1991 to 2006. The groundwater pH values changed due to the changes in their salt content from 1991 to 2006. The pH values of the surface and subsurface soil samples also changed from 1991 to 2006 that may be due to the changes in salt content of well waters. Cations and anions of the groundwater increased from 1991 to 2006. The groundwater SAR decreased for the first class (0-10) from 89 % in 1991 to 83 % in 2006 but increased for the second class (10) from 11% in 1991 to 17% in 2006. The groundwater RSC for the first and third classes changed from 91 and 3 %, respectively, in 1991 to 83 and 11%, respectively, in 2006. The increase in the high class of RSC may limit the use of these waters in irrigation. Thus, the irrigation with such water might affect the permeability of soil and cause infiltration problems.