The vulnerability of groundwater dependent ecosystems: A study on the Porsuk River Basin (Turkey) as a typical example

Groundwater dependent ecosystems can maintain their current composition and functioning by the groundwater input. Ecosystems are significantly influenced by changes in groundwater depth, pressure, flow rate and quality. Various pollutants such as pesticides, herbicides, fertilizers and other chemicals affect groundwater quality. Other pollutants having highly toxic features for environment such as industrial effluents, irrigation return-waters, and leachate from waste disposal areas may also affect groundwater quality. The Porsuk River Basin (NW of the Central Anatolia, Turkey), increasingly polluted by industrial, agricultural and municipal activities accompanied by growing population, can be considered as a typical example for groundwater dependent ecosystems. Organic and inorganic contaminants in surface and groundwater of Porsuk River Basin were assessed by collecting 32 water samples from the river and its canals and shallow and deep wells during two sampling campaigns conducted in 2001 and the obtained results were compared to the previous analysis results. These results show that both Porsuk River and groundwater in some parts of the basin have been intensively polluted in terms of NO2, NO3, NH3, NH4, phenol, AOX, phosphorus, free chlorine, sulfur, Fe, Al, Pb, Cr, Mn, Cd, and Zn. The pollution is over the allowable limits for drinking and domestic usage according to both TDWS and WHO. The abundance of aquatic Oligochaeta (especially Tubifex tubifex and Limnodrilus hoffmeisteri), bioindicators of organic pollution, along the Porsuk River also confirms these results mentioned above. On the other hand, the groundwater-surface water interaction plays a very important role on the deterioration of the groundwater quality in the Porsuk River Basin particularly during the dry period.