Summary:

Since 2007 the program called "Enhancing water storage capacity and preventing floods and drought in lowland forest ecosystems" has been implemented in the Polish forests. Its objective is to stop or slow down the outflow of surface water in the vicinity of small catchment areas and to support the development of natural landscape. The activities include, among others, the construction or renovation of several thousand water storage systems in lowland forests throughout the country. One of the major goals of the project is to support ecologically sound methods of water retention. The improvement of water balance will enhance biodiversity in forest ecosystems. This project may become the first large effort in Europe to develop small-scale water retention in forests. It analyzed the small water retention investments data already existing in Tuczno Forest Division. Analysis of the documentation showed that Tuczno Forest Division invests primarily cheap small water retention objects, environmentally friendly, made from ecological materials. These constructions often combine features of road engineering structures with backwater devices (culvert-penstock, dike). In this study, it was found that the depth and capacity of water reservoir in the 100th forest sub-compartment is less than the project intent by 4% and 10%. The cause of discrepancy there was no silting. Problem resulted from an incorrect design calculation and the execution of slightly shallower trench.