Water relations during two hydrological years in swampy areas in the Siemianice Forest Experimental Station

In recent years researchers have focused increasingly on climatic changes taking place in nature (increasing air temperature, decreasing precipitation totals). These imply changes in components of water balances and in practice changes in water relations both on the global and local scale. At present site overdrying is considered to be the biggest threat [Pierzgalski 2007]. The aim of the study is to present water relations in the forest swampy areas in a forest district (the Marianka Forest District) of the Siemianice Forest Experimental Station in hydrological years of 2005 and 2006. The investigations showed that analysed catchments, despite being located in swampy areas, are characterized by periods of water depletion in ditches. In analysed watercourses runoff was recorded from mid-November 2004 to the beginning of June 2005, while in the next hydrological year it was recorded again from mid-November, but this time longer to mid-June 2006. In relation to ground water of the catchment area a predictable relationship was observed of the water table level at the locations of observation wells. The wells located in the top sections of the catchment had water table the deepest below the ground level, while wells in valleys had water tables at the most shallow levels. It may also be stated that wells situated in higher areas (watershed), are characterized by a slightly bigger variation in the ground water table during the year than it was the case with wells located at lower points (in valleys). Both analyzed hydrological years (2005 and 2006) showed a similar pattern of ground water table at individual sites. Moreover, a marked cyclicity was recorded in the elevation of the water table, i.e. water level rising in autumn and lowering in summer months (as a result of changes in plant transpiration). The relationship of ground water levels with different forest sites found in the analyzed catchments confirms the dependence on the site moisture level variant. Water was lying at the most shallow levels in the ash-alder swamp forest site – a marshy site, while it was markedly the deepest in fresh mixed coniferous forest sites – a fresh site type. When analyzing changes in the ground water levels in terms of stand age classes we may clearly observe the seasonal variation and similar patterns of changes. Water lay the most shallow in stands of age classes V and VI. The level was significantly deepest in age class IV. The above dependencies pertained both to the hydrological year 2005 and 2006