Water quality of different aquifers in Saudi Arabia and its predictive effects on soil properties

Abstract

Chemical composition data of different aquifers was used to classify groundwaters in Saudi Arabia. For the mean water composition, different water quality parameter ranges were for EC, 1.56 to 8.24 dS m^‐1; total dissolved solids (TDS), 1200 to 4860 mg L^‐1; sodium adsorption ratio (SAR) 3.10 to 12.53; Ca²⁺/ Mg²⁺ ratio, 0.80 to 3.15; and Cl‐/SO^2‐ ₄ ratio, 0.49 to 3.68. For the 90th percentile water composition, the water quality parameter ranges were for EC, 2.26 to 13.10 dS m^‐1; TDS, 1950 to 9800 mg L^‐1; SAR, 3.45 to 18.76; Ca²⁺/Mg²⁺ ratio, 0.58 to 3.49; and Cl^‐/SO^2‐ ₄ ratio 0.40 to 4.85. Sodium was found to be the most abundant cation, followed by Ca²⁺, and Mg²⁺. Cl^‐ and SO^2‐ ₄ were present in a balanced proportion, followed by HCO^‐ ₃. The waters were classified as C ₃ S ₁ to C ₄ S ₄, i.e., a category of high to very high salinity and low to very high sodicity problem water. Other parameters such as adj. SAR, adj. R_Na+, and ESP were calculated, interrelated, and commented upon for possible salinity and sodicity hazards in soils if irrigated with these waters. The data showed a strong positive relationship between EC and TDS (r values of 0.97 for mean chemical composition and 0.95 for 90th percentile samples) and a poor correlation between EC and SAR (r values of 0.49 for mean chemical composition and 0.25 for 90th percentile sampling). A leaching requirement of 15 to 20% in excess of crop water requirements is suggested for safe use of these waters, provided proper soil, water, and crop management practices are followed under a specific land use.

Key words:

• water quality
• total dissolved solids (TDS)
• sodium adsorption ratio (SAR)
• classification
• soil salinity
• sodicity