The water regime of the long-seasonally-frozen peat soils of the Northern Trans-Ural

Northern Trans-Ural State Agricultural University, Respubliki str., 7, Tyumen, 625003, Russia

^* Corresponding author: a.s.motorin@mail.ru

Abstract

The results of many-years research of the water regime of the long-seasonally-frozen peat soils of the Northern Trans-Uralare described. It is shown that the fluctuation of groundwater in the Tarmanskoe swamp before drying is characterized by a sharp increase in levels during the spring snowmelt, then – a minimal level in summer, increase in levels in autumn, and winter minimum. The intensity of the decline in groundwater depends on precipitation (r=0.83) and evaporation. The change of groundwater level in winter is significantly affected by the progress of freezing of the upper layer and thaw. After drying at atmospheric-alluvial type of water supply of the swamp, the groundwater level during the vegetation period is determined mainly by the amount of rainfall (r=0.76). The deepest groundwater table (1.97 m) on average during the growing season set in 2012, when 56.7% of the average annual norm of precipitation fell. On the dried potter’s drainage (To=24 m, H=1.5 m) land there is no increase of the groundwater in the autumn. The lowest possible (2.5 m and more) level of the groundwater table reaches in the beginning of snowmelt in late March - early April. The magnitude of the spring rise is 1-1.5 m and depends on winter moisture (r=0.65), the snow cover and the intensity of the melting of solid precipitation. The humidity of the root layer (0.3 m) medium peat soil with a deep groundwater table (1.3 to 1.9 m) under perennial grasses is in the range of 0.5-0.6 LMC (the least moisture capacity). In the formation of the first mowing of perennial grasses, soil moisture is in the optimum range (0.6-0.85 LMC); in the high-draught years for a full second mowing has a deficit. On the boundary of the thawed and frozen layers, soil moisture is always at the upper limit of the optimum (0.85-0.95 LMC). During the winter period, the moisture reserves in the upper layer 0.5 m up to 20% due to the underlying horizons.