Groundwater quality in the Harran plain: hydrogeological characteristics, salinity, nitrate and drainage problems

Agricultural irrigation activities in the Harran Plain of Şanlıurfa, Türkiye with the Southeastern Anatolia Project (GAP) from the 1990s onwards, have affected groundwater quality. This review examines the hydrogeological characteristics of the Harran Plain, the effects of intensive agricultural practices on groundwater quality, particularly the problems of salinity and nitrate pollution, and the extent of problems arising from inadequate drainage. With the start of irrigation, a rapid increase in the groundwater level and the salinization problems on the large soils occurred as a result of excessive irrigation practices combined with inadequate drainage infrastructure. In addition, used intensive fertilizer increased the nitrate accumulation in shallow aquifers, reaching concentrations that are risky for human consumption. Current measurements conducted until 2025 show partial improvements in groundwater quality thanks to drainage improvements and more efficient irrigation management: Electrical conductivity (EC) and nitrate concentrations are trending downwards in many areas compared to the mid-2000s. However, specific parameters of many wells still do not meet drinking water standards; nitrate concentrations and EC, in particular, remain at alarming levels in the central part of the plain. In light of these findings, recommendations based on existing legal regulations are presented for sustainable groundwater management in the Harran Plain. Establishing continuous monitoring stations, ensuring inter-agency data and authority coordination, disseminating water-saving modern irrigation techniques, completing the drainage network, and updating the 1960 Groundwater Law with a comprehensive Water Law to meet current needs are proposed as critical steps.