Wielkopolska region covers the area of North European Plain with particularly unfavorable water conditions. These conditions are determined by the climate prevailing in the region, namely relatively low annual rainfall and high evapotranspiration with usually unfavorable distribution of these meteorological elements over a year. Important modulating influence can be attributed also to some non-climatic physiographical characteristics typical in vast parts of the region, mainly soil properties. In addition, evapotranspiration may be stimulated locally by vegetation. The paper comprehends initial results of hydrologic balancing of lowland catchment typical for the region of Wielkopolska. The balancing was carried out in Trojnaka Stream catchment placed in Puszcza Zielonka forest (the central Wielkopolska). High forest cover proportion, deep layer of sandy soils and high evapotranspiration shape the storage capabilities in the tested catchment. The balancing covered the average annual rainfall year (2001/2002) following average long-term rainfall period. The Period of the negative retention changes occurred from the end of April until the mid of September. The maximum decrease and increase of storage change depth occurred respectively in June (-27,7 mm) and February (50,2 mm). Average specific discharge in investigated catchment equaled 2,5 dm3∙s-1∙km-2 with maximum and minimum runoff depth respectively in January (8,8 mm) ...
Estimation of influence of land use changes to flood outflows from affor-estation areas of the Krajeńskie Lakeland was worked out basing on SCS-CN method. This method permits calculation from total rainfall a direct runoff as equivalent to effective rainfall. The original SCS-CN method in principle was worked out for catchments of cultivated areas [National Engineering Handbook 1956, 1985]. Present paper is focused on the idea of adaptation original method to forest conditions [Okoński 2006; Okoński, Miler 2010]. The main parameter of this method - CN is a function e.g. of land use. The empirical values of parameter CNemp were calculated basing on hydro-meteorological data of flood outflows at representative catchment of river no. 17-86-1 in the Krajeńskie Lakeland, in the area of the Lipka Forest District, the Biskupice Forest Range. The dependence be-tween empirical value of parameter CNemp and his equivalent's value from original method is a basis idea of adaptation method SCS-CN to characteristics of investi-gated catchment. In consequence it gives then possibility to prognoses how the change of land use, e.g. forest stand reconstruction, afforestation, deforestation, change of field culture, significant change in infrastructure etc., will influence to flood outflows (change to water retention) at a representative areas ...
A forest is the form of natural storage reservoir and it by this can be perceived as mainstay of small water retention. The prognoses of unfavourable climatic changes (growth of air temperatures, diminishing of precipitations, frequency increase of extreme weather phenomena) causing a necessity of compensations these the unfavourable phenomena by a technical and un-technical undertakings to increase water storage in forests. The building of devices of small retention has reason both: natural (i.a. assure in forest ecosystems biodiversity) and economic aspects. Indicatory cost water storage 1 m3 of water in objects of small retention is ten times smaller than in great storage reservoirs. Permission to building of objects of small retention is required for damming height 1,0 m or for every investment situated on protected areas. More than once its very increased the costs of investment. Therefore building a small objects is pragmatic, e.g. a cascade systems reservoirs. The building of objects damming and slowing outflow from catchments is focused to protection of the valuable natural habitats and it can be use full in strategy of protection of areas - may be the essential element Nature 2000 (e.g. forest bogs ecosystems, moist or flood plain forest). In Poland at ...
