Winter floods in Dviete floodplain
Winter 2012-2013 began with floods in Dviete floodplain. After continuous and intensive precipitation in autumn, water level at the bank of Dviete old riverbed at Putnu sala had raised for about 1.7-1.8 meters in the first half of November, if compare with summer period. As a result, most of ground-water monitoring wells were over-flooded again. Absolute height of the water level reached 88.1 meters about see level, and only three monitoring wells were above it, located further away from the oxbow. Thus the scale of these floods was similar to moderate spring floods.
In the second half of November the amount of precipitation considerably decreased, and water level at the banks of Dviete old riverbed began to fall. At the beginning of December air temperature in the region constantly fell below 0oC, and prolonged frost set in. As a result, at the water level of 87.6 m, wide areas of floodplain were covered with thick ice, and 7 out of 15 monitoring wells were completely under the ice. In the second half of December thickness of ice cover increased till 10-15 cm, water level continued to decrease, thus monitoring wells were exposed to large static pressure, which was not foreseen. In the first half of January, when heavy ice cover landed and split, most of the wells were more or less pressed in the ground (even for 20-30 cm). Many metal covers of monitoring wells were damaged, some upper parts of the wells were deformed as well. In the beginning of February two monitoring wells of the LIFE+ project as well as all the wells, arranged before the LIFE+ project at the bank of Dviete oxbow, were still under the ice.
As a consequence, the data, obtained in monitoring wells, damaged by the pressure of ice cover, in January and February, 2013, are not comparable with previously obtained data for the present, and restoration of monitoring wells will be needed.
Dāvis Gruberts
08.02.2013.
