Determination of the underground water potential of Şırnak Silopi Plain with geographical information system

Groundwater is a vital source of freshwater that accumulates under natural conditions within permeable underground formations and can be accessed through human activities. Especially due to factors such as climate change, seasonal irregularities in surface water resources, and increasing water demand, groundwater has gained strategic importance in many regions. However, the sustainable management of these resources depends not only on their existence but also on accurately determining their potential in terms of quantity and quality. A sound assessment of groundwater potential is of great importance for both planning current usage and developing policies to meet future needs. In this context, scientific studies conducted using modern technologies and spatial analysis methods make significant contributions to identifying groundwater potential. This study aims to determine the groundwater potential of the Silopi Plain, located in the Şırnak province in the southeastern part of Türkiye, covering an area of approximately 333 km². The region meets most of its agricultural irrigation needs through groundwater extracted from wells opened in previous years. According to updated local data verified by technical staff, the number of active wells in the plain exceeds 1.000 (Anonymous, 2024). Increasing water demand and intensive utilization necessitate a detailed spatial analysis of the region's groundwater resources. Within the scope of this study, analyses supported by Geographic Information Systems (GIS) were utilized to reveal the spatial distribution of groundwater levels. Commonly used interpolation methods such as Inverse Distance Weighted (IDW), Radial Basis Function (RBF), and Kriging were applied to produce thematic maps. The analysis was based on hydrogeological parameters collected from 310 groundwater wells, including dynamic water level (m), static water level (m), and well yield (L/s). The results showed that static water levels ranged between 6,3 and 190 meters, while dynamic levels varied between 20 and 280 meters. These findings demonstrate significant regional variations across the plain. According to the IDW-based analysis of dynamic water levels, 61,1%of the study area (20,228 ha) falls within the 72 – 125 m range, followed by 36.3%within the 20 – 72 m depth interval. Together, these two ranges represent 97,4%of the total area, indicating that the majority of groundwater is concentrated within these depth intervals. However, approximately seven wells were found to have critically low water levels, classifying them as high-risk zones. Although RBF and Kriging methods produced slightly different areal distributions, their results showed a high level of similarity with those of IDW. Regarding static water levels, IDW results indicated that 95,1%of the study area had groundwater levels between 0 – 77 m. This ratio was even higher in the RBF and Kriging methods, with 98,6%and 98%, respectively. The proportion of disadvantaged wells (with low levels) was slightly over 2%. Geographically, the southern part of the plain borders the Hezil River, while the northern part lies at the foothills of Mount Cudi. Based on rainfall patterns and geological structure, it is inferred that the groundwater flow regime runs from north to south and may also receive recharge from Iraq in the south. Therefore, groundwater potential is relatively higher in the southern sections of the plain. In terms of well yield, results from all three interpolation methods revealed a consistent response in relation to dynamic and static water levels. Approximately 69,7%to 79,9%of the area was found to have yields between 12,1 – 38 L/s. Consequently, the groundwater reserves of the Silopi Plain appear to possess a higher potential compared to nearby regions such as Nusaybin, Kızıltepe, and Viranşehir. This condition is primarily attributed to the recharge from the Mount Cudi region.