Application of Geographic Information System (GIS) to study the influence of the groundwater irrigation on salt accumulation in the soils of Sohag governorate

摘要

Sohag governorate is located in Upper Egypt (about 467 Km south Cairo city) in a narrow long strip of cultivated area. The total maximum length of Sohag governorate is about 96 Km and the maximum width is about 25 Km. Sixteen transects were selected, crossing the Nile valley and extending from the eastern to the western desert covering the area understudy. Two locations on each side of the river from each transect whenever it is possible. Soil and water samples were selected to study physical and chemical properties of soils and water wells, to identify effect groundwater irrigation on salt accumulation in this area with a special reference to their taxonomic units. The obtained data reveal that the values of electrical conductivity, (ECw) varied from well to another. The ECw values of well waters range from 8020 μS/cm to 500 μS/cm. In soil samples, The ECe reached a maximum value of 8.23 dS/m and 10.85 dS/m for surface and subsurface soils respectively. However, the lowest value was 0.36 dS/m and 0.43 dS/m for surface and subsurface soils respectively. The salinity is increase with depth in most cases. The correlation coefficients between the electrical conductivity of the groundwater (ECw) and the saturated soil extract (ECe) are positive. The groundwater pH value ranges between 7.78 and 8.83. The pH values of the surface and subsurface soils samples are over than 8. The soluble potassium range from 0.05 to 0.62 meq/le in groundwater. But, in the soil samples the soluble potassium values ranged from 0.08 to 0.61 meq/le and from 0.09 to 0.65 meq/le for the surface and subsurface soil samples respectively. Sodium values in the groundwater had a range of 2.11 to 48.19 meq/l.It is ranged from 1.20 to 67.08 meq/le and 3.00 to 60.28 meq/le for the surface and subsurface soils samples respectively. Calcium values in the groundwater are varying from 0.86 to 10.60 meq/l. It is values ranged from 0.06 to 10.33 meq/le and 0.20 to 16.00 meq/le for the surface and subsurface soil samples respectively. Magnesium values in the groundwater ranged from 0.40 to 7.60 meq/l. Soluble magnesium values had a range of 0.20 to 10.40 meq/le and 0.20 to 8.79 meq/le for the surface and subsurface soil samples respectively. Chlorides values in the groundwater ranged from 1.19 to 45.00 meq/l. It is values ranged from 0.29 to 46.84 meq/le and 0.8 to 30.20 meq/le for the surface and subsurface soil samples respectively. Soluble sulphates values in the groundwater ranged from 0.92 to 16.20 meq/l. It is values ranged from 0.41 to 31.25 meq/le and 0.32 to 29.15 meq/le for the surface and subsurface soil samples respectively. Carbonates and bicarbonate values in the groundwater ranged from 1.33 to 15.60 meq/l. It is values ranged from 0.75 to 19.20 meq/le and 0.8 to 18.40 meq/le for the surface and subsurface soil samples respectively. SAR values in the groundwater ranged from 1.56 to 18.48. In the surface and subsurface soil samples, SAR values had a range of 1.16 to 48.09 and 2.73 to 51.15 respectively. RSC values in the groundwater reached high from 0.00 to 5.60. SSP values in groundwater ranged from 27.62 % to 83.43 %. In the surface and subsurface soil samples, SSP values had a range of 10.88 % to 95.16 % and 45.88 % to 95.64 % respectively. Calcium carbonate values in the surface and subsurface soil samples range between 0.04 to 37.39% and 0.09% to 29.57% respectively. The soil survey of area understudy identified medium to coarse textured soils .The soil under consideration were classified according to Soil Taxonomy as: Typic Torripsamments, Typic Torrorthents, Sodic Torrorthents, Typic Hplocalcids and Typic Natrargids.