CHARACTERISTICS OF AGRICULTURAL DRAINAGE WATER IN BAHRAIN

The quality of agricultural drainage water throughout the State of Bahrain has been investigated with respect to pH, salinity, conductivity, bicarbonate, chloride, sulfate, sodium, potassium, magnesium, calcium, fluoride, boron, nitrate, nitrite, ammonia and phosphate. The quality of drainage water reflected the quality of groundwater due to the exclusive use of groundwater for irrigation purposes. Drainage water showed high salinity, sodium and chloride with ranges of 4.0-46.0 ppt, 645-14820 mg l-1 and 1400-26692 mg l-1, respectively. Elevated concentrations of bicarbonate, sulfate and calcium were also measured with ranges of 140-352, 1316-3617 and 512-990 mg l-1, respectively. Nutrient concentrations were generally low except in certain areas. The discharge of drainage water directly into the shallow intertidal zone may have an adverse impact on the marine environment. The average quantity discharged is approximately 2.0 x 10(7) m3 year-1. The quality and quantity of drainage water was assessed for reuse for irrigation purposes.