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

Abstract

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.

Keywords

• Harran Plain
• Groundwater quality
• Salinity
• Nitrate pollution
• Drainage
• Hydrogeology
• GAP project
• Irrigation management

References

1. Ağca, N. & Ergezer, Ş. (1995). Harran ovası topraklarında drenaj, tuzluluk ve alkalilik sorunları. Harran Üniv. Ziraat Fak. Derg. 1(3), 81-90.
2. Atasoy, A. D. & Yesilnacar, M. I. (2010). Effect of high sulfate concentration on the corrosivity: a case study from groundwater in Harran plain, Turkey. Environ Monit Assess 166:595-607.
3. Aydogdu, M. H., Karli, B. & Aydogdu, M. (2015). Evaluation of attitudes of stakeholders for irrigation water management: A case study of Harran Plain, Turkey, Journal of Environmental and Agricultural Sciences, 4, 42-47.
4. Bilgili, A. V., Yeşilnacar, M. I., Akihiko, K., Nagano, T., Aydemir, A., Hızlı, H. S. & Bilgili, A. (2018). Post-irrigation degradation of land and environmental resources in the Harran plain, southeastern Turkey, Environ Monit Assess 190:660.
5. Bilgili, A. V., Cullu, M. A., van Es, H., Aydemir, A., & Aydemir, S. (2011). The use of hyperspectral visible and near infrared reflectance spectroscopy for the characterization of salt affected soils in the Harran plain, Turkey, Arid Land Research and Management, 25, 19–37.
6. Çullu, M. A., Almaca, A., Sahin, Y. & Aydemir, S. (2002). Application of GIS for monitoring salinization in the Harran Plain, Turkey (pp 326-331). International conference on sustainable land use and management, Canakkale, Turkey.
7. DSI (2003) Problems of drainage and salinity in the Harran Plain: summary report. The 15th District Directorate of the State Hydraulic Works, Sanliurfa, p 10 (in Turkish).
8. DSI (2008) Groundwater level observations in the Harran Plain: summary report, The 15th District Directorate of the State Hydraulic Works, Sanliurfa, Turkey (in Turkish).

9. DSI (2015). Groundwater level observations in the Harran Plain: summary report. 15th District Directorate of State Hydraulic Works, Sanliurfa, Turkey (in Turkish)
10. Kahraman, N., Yazıcı Karabulut, B., Atasoy, A. D., & Yesilnacar, M. I. (2016). Harran Ovasi Serbest Akiferinde Yaz ve Kış Dönemleri Nitrat Kirliliginin Arastirilmasi (2014-2015). Harran Universitesi Muhendislik Dergisi, 1(2), 1–8 (In Turkish).
11. Kara, H., Demir Yetiş, A. & Kalkan, S., (2022). The impact of geothermal fluid discharge on drainage water and groundwater quality in terms of toxic contaminants in the agricultural Harran Plain, Turkey. Geothermics 105, 102502.
12. Kara, H., Demir Yetiş, A., Kalkan, S. & Yetiş, R. (2023). Evaluation of pollution indicators and transported sediment content in agricultural drainage waters for reuse as irrigation, Harran Plain, Turkey. Environmental Science and Pollution Research. 30:64982–64993.
13. Kara, H. (2025). The prediction of heavy metal contamination in groundwater using machine learning algorithms: a case study from the Harran Plain, a major agricultural irrigation area in Türkiye. Environ Geochem Health, 22;47(8):328.
14. Karabulut, A. İ., Yazıcı Karabulut, B., Demir Yetiş, A., Yeşilnacar, M. İ. & Derin, P. (2023). Socioeconomic driving forces of land use/cover changes in the semi-arid Harran plain and their probable implications on arising groundwater level, the GAP area of southeastern. Acta Geophysica 71, 2795-2810.
15. Kendirli, B., Cakmak, B. & Ucar, Y. (2005). Salinity in Southeastern Anatolia project (GAP) Turkey: issues and options, Irrig Drain 54:115–122.
16. Ozdogan, M., Woodcock, C. E., Salvucci, G. D. & Demir, H. (2006). Changes in summer irrigated crop area and water use in southeastern Turkey from 1993 to 2002: implications for current and future water resources, Water Resour Manage 20:467–488.
17. Singh, B., Singh, B. P. & Cowie, A. L. (2010). Characterisation and evaluation of biochars for their application as a soil amendment. Soil Res 48(7):516–525.
18. Sonmez, O., Aydemir, S., Kaya, C., Çopur, O., Gerçek, S., Bilgili, A. V., & Sürücü, A. (2011). The impact of irrigation performance, phosphorous fertilizer and soil tillage on sediment losses as a result of surface erosion due to excessive irrigation. TUBITAK Project No: 108O163.
19. Yazıcı Karabulut, B. & Karabulut, A.İ., (2025). Temporal Analysis of Groundwater Quality in the Harran Plain: Linking Land Use Change to Water Contamination (2005–2025), Environmental and Earth Sciences Proceedings, 36(1), 4.
20. Yenigun, I. (2009). Determination of some water quality parameters of deep aquifer of the Harran Plain. Dissertation, Harran University Graduate School of Natural and Applied Sciences, Department of Environmental Engineering, Turkey, p 102 (in Turkish with English abstract).
21. Yesilnacar, M.I., Demir, F., Uyanik, S., Yılmaz, G. & Demir, T. (2007). Determination of groundwater quality and pollution potential of the Harran Plain, Sanlıurfa, Turkey. The Scientific and Technological Research Council of Turkey, TUBITAK, Grant number: 104Y188, p 88 (in Turkish).
22. Yesilnacar, M. I. & Gulluoglu, M. S. (2007). The effects of the largest irrigation of GAP project on groundwater quality, Sanliurfa-Harran, Fresenius Environ Bull 16(2):206-211.
23. Yesilnacar, M. I. & Gulluoglu, M. S. (2008). Hydrochemical characteristics and the effects of irrigation on groundwater quality in Harran plain, GAP Project, Turkey, Env Geol 54(1):183-196.
24. Yesilnacar, M. I. & Uyanik, S. (2005). Investigation of water quality of the world’s largest irrigation tunnel system, the Sanliurfa Tunnels in Turkey. Fresenius Environ Bull 14(4):300-306.
25. Yeşilnacar, M. I., Atasoy, A. D., Kumral, M., Dülgergil, Ç. T., & Aydoğdu, M. (2013). Yeralti Sularinda Yuksek Florurun Olusumu, Dagilimi, Insan Sagligina Etkileri ve Florur Gideriminin Arastirilmasi, KB Sanliurfa. TUBITAK project no: 110Y234. Sanliurfa, Turkey (In Turkish).
26. Yesilnacar, M. I., Sahinkaya, E., Naz, M., & Ozkaya, B. (2008). Neural network prediction of nitrate in groundwater of Harran plain, Turkey. Environmental Geology, 56, 19–25.
27. Yesilnacar, M. I., Yetiş, A., Dülgergil, C., Kumral, M., Atasoy, A. & Tuba, R. (2016). Geomedical assessment of an area having high-fluoride groundwater in southeastern Turkey, Environmental Earth Sciences, 75, 162.
28. Yetim, S., & Kara, H. (2011). Determination of sediment and toxic element contents and some quality parameters of water carried in drainage canals in the Harran Plain, GAP region (in Turkish). TÜBİTAK (Proje No:109O421).
29. Yetiş, D. A., Kahraman, N., Yeşilnacar, M. I. & Kara, H. (2021). Groundwater Quality Assessment Using GIS Based on some Pollution Indicators over the Past 10 Years (2005-2015): a Case Study from Semi-Arid Harran Plain, Turkey, Water Air Soil Pollut 232: 11, 1-17.