101. Water Balances of the Northern Catchments of Finland

This paper discusses the water balances of three basins in northern Finland, between latitudes 66 and 69°N. Drainage areas vary from 11.6 to 16.4 km2. The Vaha-Askanjoki basin is completely covered by forest, the Iittovuoma basin is practically treeless, and the Laanioja basin is covered by forest to a major extent. Otherwise, conditions are quite similar in all three basins. Discharges are measured continuously, precipitation on a daily basis, and snow water equivalent (SWE) once or twice a month. Data series are 25–45 years long. The average water balance components were P corrected = 640 mm, Q = 409 mm and ET = 231 mm. There was no trend in SWE in the north, but quite a strong decreasing trend in southern Finland (62°N). A slight increasing trend in the evapotranspiration of the two forested basins was seen. The estimation of true areal precipitation is the most critical parameter in water balance calculations.