Monthly hydrological report in February 1999
Apart from a very cold spell at the beginning of the month, February was somewhat warmer than normal for the time of year. Precipitation was exceptionally heavy in the southern coastal zone, where considerable accumulation of snow occurred. Water
surfaces decreased in the manner typical for the winter season, but remained above their seasonal mean levels in many larger lakes and groundwater formations. Water accumulated over ice layers in many areas with high amounts of snow.
Precipitation in the southernmost Finland reached 200% of the seasonal mean in many areas and as much as 300% along the coastal zone of the Gulf of Finland. In other parts of the country the precipitation was 100-180% of the seasonal mean.
The water equivalent of the snow cover increased throughout the country, particularly in the south, in proportion to the precipitation. In most areas, however, the water equivalent was below or only equal to the seasonal mean. In the counties of
Uusimaa and Kaakkois-Suomi the amount of snow was greater than generally in recent years, although by comparison with the long-term mean the amount of snow was only approximately normal, except for a thin coastal zone where exceptionally heavy snowfalls
occurred. Accumulation of snow varied greatly between different areas because of uneven distribution of falling snow.
Water levels in the larger lakes remained above the seasonal mean almost throughout the country. The level of lake Saimaa did not change during February. In some smaller watercourses the water level decreased to the seasonal mean level or even lower.
The deviations of water levels from the seasonal mean at the end of February were: Pielinen+28 cm, Kallavesi +2, Saimaa +48, Keitele +7, Päijänne +3, Pyhäjärvi, Säkylä +17, Längelmävesi +19, Näsijärvi +2, Lestijärvi +17, Lentua +3, Oulujärvi +33, Lokka
+71 and Inari -5 cm.
Discharges were higher than the mean for February in many larger rivers but close to the mean in smaller watercourses. The monthly discharge of the river Pielisjoki was 95% of the mean February discharge for the period 1961-1990 and corresponding
figures in some other river watercourses were: Vuoksi and Kymijoki 117 %, Paimionjoki 112, Kokemäenjoki 113, Kalajoki 103, Oulujoki 111, Iijoki 101, Kemijoki 130 and Tornionjoki 116%.
Groundwater levels varied on both sides of the seasonal mean; in most parts of the country, however, groundwater levels were still above the mean due to the prolonged wet weather during 1998. Groundwater levels decreased in all areas. The depth of the
groundfrost was hihger than normally in the southt and west but lower than normally in the east.
Lake ice. In many places water flooded on the ice surface from the lake. This water did not in all cases freeze to the surface of the blue ice to form a compact layer of snow ice. The following total thicknesses of lake ice were recorded at the end of
the month: Tuusulanjärvi 51 cm Sääksjärvi 49, Saimaa, Lauritsala 35, Kallavesi 63, Oulujärvi 55, Unari 62, Inari 53 and Kilpisjärvi 74 cm. In most places with strong water currents the ice was thinner than generally in the area.