The study area encompasses the cities of Mersin and Tarsus which are located along the southern coast of Turkey. The Berdan River is the largest stream in the area, with a length of 124 km and a mean annual discharge of about 39.73 m3/s. The climate is temperate Mediterranean with a mean annual precipitation of 594.6 mm and a mean annual air temperature in the coastal zone is 18.5 °C.

Study area with CrITERIA sampling points in Mersin, Turkey.

Based on the lithologic properties of the geologic units, the hydrostratigraphic sequence in the study area includes, from bottom to top, a karstic aquifer comprising of Paleozoic and Neogene carbonates, a confined granular aquifer of Neogene formations, and an unconfined granular aquifer of Quaternary units at the coastal zone. The Paleozoic carbonates are overlain tectonically by an ophiolitic mélange that includes Mesozoic aged limestone blocks. This part of the geologic sequence crops out mainly in the mountainous part of the study area and is covered by the Neogene aged carbonate formations that are located at the south. The alluvial deposits of the coastal aquifer consist of a heterogeneous mixture of gravel, sand, silt, and clay.

Tarsus and the central districts of Mersin have a population of 1,279,067. The annual domestic water consumption was 100.7 hm3 in 2015 for both Mersin and Tarsus. Agriculture is also a very common and an important sector in the area with water consumption for irrigation to be 279.19 hm3. A significant amount of the drinking and irrigation water demands is supplied by the Berdan Dam, located to the northeast of the studied region. However, groundwater is also widely used for domestic, agricultural, and industrial purposes. The industries are mainly chemical and food industries. Moreover, an increasing number of summer resorts which are located mostly along the western coast, meet their domestic water demand from groundwater via private wells.

Despite the extensive groundwater use, particularly in the coastal plain, the negligible magnitude of seawater intrusion indicates a strong recharge from the Taurus Mountains that flow through the aquifer system. CrITERIA has been repeatably collecting and analyzing groundwater samples from 52 sites in the area.