PROCEEDINGS OF THE LATVIAN ACADEMY OF SCIENCES. Section B, Vol. 70 (2016), No. 2 (701), pp. 78–87. DOI: 10.1515/prolas-2016-0013 LONG-TERM CHANGES IN THE WATER TEMPERATURE OF RIVERS IN LATVIA Inese Latkovska1,2 # and Elga Apsîte1 1 Faculty of Geography and Earth Sciences, University of Latvia, Jelgavas iela 1, Rîga LV-1004, LATVIA, e-mail:
[email protected] 2 Latvian Environment, Geology, and Meteorology Centre, Maskavas iela 165, Rîga LV-1019, LATVIA # Corresponding author Communicated by Mâris Kïaviòð The study describes the trends of monthly mean water temperature (from May to October) and the annual maximum water temperature of the rivers in Latvia during the time period from 1945 to 2000. The results demonstrated that the mean water temperatures during the monitoring period from May to October were higher in the largest rivers (from 13.6 oC to 16.1 oC) compared to those in the smallest rivers (from 11.5 oC to 15.7 oC). Similar patterns were seen for the maxi- mum water temperature: in large rivers from 22.9 oC to 25.7 oC, and in small rivers from 20.8 oC to 25.8 oC. Generally, lower water temperatures occurred in rivers with a high groundwater inflow rate, for example, in rivers of the Gauja basin, in particular, in the Amata River. Mann-Kendall test results demonstrated that during the monitoring period from May to October, mean water tem- peratures had a positive trend. However, the annual maximum temperature had a negative trend. Key words: water temperature, long-term changes, river, Latvia.