Salinity and Sodicity of Well Waters and Soils at the Red Sea Coastal Region

Fatima Ali Mohamed Ahmed, Mukhtar Ahmed Mustafa

Abstract


The quality of replicate well water samples collected in winter and summer from the coast at Dongonab, Arbaat, and Arim was assessed. Soil samples, at the three coastal locations were collected by an auger from E-S transects extending 7 km from the seashore inland. Along each transect, soil samples were collected from three consecutive sites at 0.01, 3.5 and 7.0 km from the seashore. At each site, replicate soil samples were collected from the following four successive depths: 0-10, 10-30, 30-60 and 60-90 cm. Standard procedures were used for determining the salinity and sodicity of the water and soil samples. In Summer the electrical conductivity of well waters (ECw) were 5.0 dS/m at Arbaat, 6.9 dS/m at Dongonap and 14.3 dS/m at Arim with a mean of 8.7 dS/m and a C.V. of 56.3%. Sodium adsorption ratio (SAR) of well waters (SARw) was 2.4 at Arbaat, 15.6 at Dongonap and 16.8 (mmole+/l)0.5 at Arim with a mean of 11.6 and a C.V. of 68.9%. Lower values were found in winter with mean ECw and SARw values equal to 7.9 dS/m and 10.5 (mmole+/l)0.5, respectively. In general, the texture of the soil profiles in the three locations was sand at a distance of 0.01 km from the seashore inland and loamy sand at 3.5 km and 7.0 km. In Arim, the mean electrical conductivity of the saturation extract (ECe) was 58.6 dS/m at 0.01 km, 2.3 dS/m at 3.5 km and 1.1 dS/m at 7.0 km. In Arbaat, the mean ECe was 86.7 dS/m at 0.01 km, 6.8 dS/m at 3.5 km and 2.2 dS/m at 7.0 km. In Dongonap, the mean ECe was 38.5 dS/m at 0.01 km, 13.0 dS/m at 3.5 km and 4.6 dS/m at 7.0 km. At each of the three locations, both ECe and SAR decreased significantly (P < 0.001) with increase of distance according to quadratic trend lines. At a distance of 0.01 km away from the coast the soil profile was very highly saline and sodic at the three locations. At a distance of 3.5 km, the soil profile was non-saline and non-sodic at Arim, highly saline and sodic at Arbaat and saline sodic at Dongonap. At 7.0 km the soil profile was non-saline non-sodic at Arim and Arbaat and slightly saline and non-sodic at Dongonap.

Keywords


ECe; SAR; spatial variation;seasonal variation; Red Sea State

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