Efekty realizacji programu małej retencji w lasach na przykładzie dwóch nadleśnictw obszarów nizinnych

Evaluation of the effects of small retention programme implementation was an aim of the paper. The research was carried out in two forest districts located in lowland area: Włocławek and Dąbrowa Forest District. They are located in the central part of the Polish Lowland in the southern and north-eastern part of Kujawy-Pomerania Province. Location of these objects in the zone of the lowest precipitation and also in the high air temperature have negative impact on the water resources. All of the activities which can protect the water resources as well as can increase the water retention should be priority. Realization of the investment of small retention objects in recent years caused creation of artificial reservoirs collecting significant amount of water, which flowed away until now. Realization of small retention object at Osięciny Forestry of Włocławek Forest District included building weir with regulated flashboard gate in the ditch. Meanwhile in the Dąbrowa Forest District at Krępa watercourse at degraded grasslands of low class in November 2006. Four cascading weir with constant overflow as well as four reservoirs were built. An increase of surface and subsurface retention capacity in Włocławek Forest Districts was from 14 to 14.5 th. m3, with an increase of flowed area from 10.3 th. m2 to 31.7 th. m2. Flowed area created in second analysed forest district – Dąbrowa, was from 1.8 th. m2 to 32.9 th. m2, and built reservoirs stored water of amount from 2.6 th. 3 to 18.1 th. m2. The building devices of small retention caused the water retention increase of about 36.4 th. m3 in total. Improvement of habitat conditions which are in particular sensitive to water shortage, which can appear frequently, was an additional profit of small retention programme implementation, besides the increase of water storage amount. The researches indicated that nature-friendly small water damming devices, constructed from natural materials can also be an cheap alternative for water storage in comparison to constructing bigger water reservoirs, which also demanding high exploitation costs. Small retention water devices presented in the paper allow to carrying out a rational water management with maintain of environmental needs. They also indicate possibility of water retention increase and protection of forest habitats which are particularly sensitive to water shortage. The more so all of the small retention activities can positively affect biodiversity of forest habitats.