Monthly hydrological report November 2014

Snow levels below the mean, high discharges in the rivers of Pohjanmaa

Snow water equivalent in November 2014

November was rather mild in southern and central Finland. Precipitation was low in the south and in Lapland, but clearly above the mean in a region extending from Pohjanmaa to Kainuu. Snow levels were below the mean. Precipitation increased water levels and discharges particularly along the western coastline. In most parts of the country groundwater levels had increased above the seasonal mean. An ice cover developed over lakes in Lapland.

Precipitation

Great regional variation was recorded in precipitation in November. In northern Lapland the precipitation figures were in some areas below 20 mm, whereas in an area extending from Pohjanmaa to Kainuu the monthly precipitation of 60-100 mm was 1.5-fold the seasonal mean. In Lapland and also in southern Finland, the recorded precipitation was only about half the mean for November. Elsewhere, precipitation varied on both sides of the seasonal mean. Most of the precipitation occurred during the first half of the month.

Snow

Snow covers in November were below the seasonal mean. At the beginning of the month, snow was recorded only in northern Lapland, and although a transient snow cover was formed almost throughout the country, by mid-November most of the country was again free of snow. Towards the end of the month the snow burden increased in southern Lapland and in northern parts of Kainuu, but elsewhere there was very little snow. By the last day of the month there was almost no snow at all below a line from Oulu to Kajaani, and from there northwards to Muonio the water equivalent of the snow cover was generally below 20 mm. In northern Lapland the water equivalent was generally 20-50 mm.

Water level and discharge

Lake water levels in Lapland were generally decreasing and discharges were low throughout the month, but elsewhere the precipitation early in November increased both water levels and discharges. In many rivers of Etelä-Pohjanmaa the discharges exceeded typical spring flood levels, but no major flood damage was recorded. The discharges of coastal rivers in Pohjois-Pohjanmaa also increased considerably due to the high precipitation. Lake water levels increased most in a region of high precipitation extending from the western coast to Kainuu. For example the level of lake Kallavesi, which had been rather low, increased by almost half a metre during November and was clearly above the seasonal mean by the end of the month. At this time, the lake level increases were levelling and many even turned towards a decrease. Lake water levels at the end of November varied on both sides of the seasonal mean.

Mean discharges during November were clearly above the seasonal mean in Pohjois-Pohjanmaa. Elsewhere, the discharges were below or close to the seasonal mean.

The deviation of the level of lake Pielinen from the seasonal mean at the end of November was -13 cm, and corresponding figures in some other lakes were: Kallavesi +21 cm, Saimaa -7, Keitele -9, Päijänne -11, Pyhäjärvi, Säkylä -20, Längelmävesi -26, Näsijärvi -5, Lappajärvi +34, Lammasjärvi +18, Oulujärvi +21, Lokka -65 and Inari -11 cm. The mean monthly discharge of the river Pielisjoki was 85% of the mean November discharge during the reference period 1971-2000, and corresponding figures in some other rivers were: Vuoksi 92%, Kymijoki 59, Karjaanjoki 49, Kokemäenjoki 55, Siikajoki 235, Oulujoki 114, Iijoki 197, Kemijoki 80 and Tornionjoki 77%.

Groundwater level

Groundwater levels were increasing in all areas with the exception of northern and central Lapland. In most parts of the country the levels finally increased above the seasonal mean. Groundwater levels in southern and central Finland and in southern Lapland were 0-20 cm above the seasonal mean. Elsewhere in northern Finland the water levels were 10-50 cm below the seasonal mean.

Groundfrost

Groundfrost was recorded in parts of eastern and northern Finland to depths of 0-15 cm.

Surface water temperature and ice cover

Most northern lakes froze over rather early, some smaller lakes even at the end of October. By the end of November lake ice covers were generally 20-35 cm in Lapland and below 20 cm in Pohjois-Pohjanmaa and Kainuu. These figures were close to the seasonal mean. In southern and central Finland the lakes were generally still unfrozen; water temperatures were generally 0-4°C.

Maps, graphs and tables

Published 2015-01-30 at 18:06, updated 2015-01-30 at 18:03