Monitoring Water Quality and Quantity of National Watersheds in Turkey Berkant Odemis & Fatih Evrendilek Received: 21 August 2006 / Accepted: 30 October 2006 / Published online: 14 December 2006 # Springer Science + Business Media B.V. 2006 Abstract National data from the hydrological net- work for 38 rivers out of 25 watersheds were used to detect spatial and temporal trends in water quality and quantity characteristics between 1995 and 2002. Assessment of water quality and quantity included flow rate, water temperature, pH, electrical conduc- tivity, sodium adsorption rate, Na, K, Ca+Mg, CO 3 , HCO 3 , Cl, SO 4 , and boron. Among the major ions assessed on a watershed basis, Turkish river waters are relatively high in Ca+Mg, Na and HCO 3 , and low in K and CO 3 . The watersheds in Turkey experienced a general trend of 16% decrease in flow rates between 1995 and 2002 at a mean annual rate of about 4 m 3 s -1 , with a considerable spatial variation. Similarly, there appeared to be an increasing trend in river water temperature, at a mean annual rate of about 0.2°C. A substantial proportion of watersheds experienced an increase in pH, in particular, after 1997, with a maximum increase from 8.1 to 8.4 observed in Euphrates (P <0.01). Kendall’s tau test revealed increasing trends of EC and SAR concentrations that exceeded existing standards, particularly, in the Meriç, Kızılırmak and Big Menderes watersheds where intensive agricultural activities take place. Such continued levels may threaten biotic integrity and both drinking and irrigation water quality of rivers. Best multiple linear regression (MLR) models con- structed both annually and monthly differed in R 2 values in accounting for variations of pH and water temperature only. The findings of the study can provide a useful assessment of controls over water quality and quantity and assist in devising integrated and sustainable management practices for watersheds at the regional scale in Turkey. Keywords Watershed management . Sustainable development . Water quality . Water quantity . Climate change . Turkey 1 Introduction The total stock of renewable water resources of the world is estimated at 42,650 km 3 yr -1 , and human population has access to about 9,650 km 3 yr -1 of stable runoff when the amount of water discharging into the sea (28,000 km 3 yr -1 ) and seasonal character- istics of the runoff (5,000 km 3 yr -1 ) are taken into account (Shiklomanov, 2000; Simonovic, 2002). Quality and quantity of river waters worldwide are Environ Monit Assess (2007) 133:215–229 DOI 10.1007/s10661-006-9574-1 B. Odemis Department of Farm Structures and Irrigation, Mustafa Kemal University, 31034 Antakya-Hatay, Turkey F. Evrendilek (*) Department of Landscape Architecture, Mustafa Kemal University, 31034 Antakya-Hatay, Turkey e-mail: fevrendilek@mku.edu.tr