Thessaly basin. This large area of 13,377 square kilometers covers almost the entire geographical region where water shortages are a major problem, as is pollution in the Pineios River and Pagasitic Gulf. High nitrate concentrations are present in the area around Argyropoulio, Achilleio, Ayia and Platykambos, mostly due to intensive farming methods. In the prefecture of Karditsa, high concentrations of ammonia have been found in Mataraga because of the large number of livestock farms and salinization is evident in the coastal areas of Mavrovouni, Mt Pelion and northern Orthyos. At present, underground water is being overused, so drilling is going even deeper; coastal areas are suffering from salinization and subsidence is occurring in several areas.