GEOCHEMISTRY OF ARTIFICIAL WETLANDS IN AN ARID CLIMATE

Municipal centres and agricultural areas in Saudi Arabia generate significant wastewater outflows that consist predominantly of low salinity treated sewage effluent. While a portion of the wastewater is reused, significant quantities of wastewater are also discharged at surface. In parts of the Eastern Province (e.g., the Hofuf area) the wastewater discharges have augmented the size of existing wetlands originally recharged by natural springs, while elsewhere the discharges have resulted in the formation of new open water bodies/wetlands. The good water quality of those wetlands supports diverse bird, mammal and reptilian populations, which attract the attention of the local communities who use the wetland areas for recreation and/or farming. The hot and arid climate, however, results in the salinization and/or sabkha formation in the wetland’s sections distal to the outflow source(s), which is associated with loss of vegetation and biodiversity. Therefore, it is important to understand the impact of processes such as evaporative loss, mineral dissolution and precipitation and water/mineral interaction on the long-term fate of the wetlands. This presentation will discuss the final results of a geochemical study that utilized various isotope and dissolved element indicators (e.g., d¹⁸O, d²H, d¹³C, ⁸⁷Sr/⁸⁶Sr, Cl/Br and Cl/B) to better understand the water and solute balances of two wetlands in the Eastern Province - one recharged by a mixture of local shallow groundwater and a municipal wastewater outflow from a local deep groundwater aquifer, and another recharged by municipal/agricultural water outflow originating predominantly from a groundwater aquifer traditionally used for irrigation. The results of this study will contribute to our understanding of the fate of artificial (engineered) and/or natural wetlands in arid climates.