Restoring Water Retention in Polish Forests to Combat Climate Impacts

Implementation focused on increasing small-scale water retention in forest ecosystems through widespread construction and upgrading of hydrotechnical structures designed to slow runoff, raise groundwater levels, and rebuild wet forest habitats.

A larger programme was implemented by the State Forests between 2010 and 2015 across 175 forest districts within 17 Regional Directorates. The intervention consolidated multiple earlier retention investments into a single coordinated initiative designed to retain surface and groundwater within watersheds administered by the State Forests while supporting natural landscape functions. Implementation involved constructing, expanding, or modernising several thousand retention structures, including small reservoirs and a range of water-control and conveyance elements (gates, weirs, culverts and fords). Activities were grouped into three functional types: retaining water, damming water, and slowing the outflow of surface water. A key implementation approach was to modify and reconstruct existing land improvement and drainage systems so they would reduce excessive drainage and instead slow runoff (for example, damming water in ditches and managing flows to and from reservoirs, ponds and other depressions connected to ditch networks).

A subsequent nationwide programme ran from 2016 to 2023 under the Operational Programme Infrastructure and Environment 2014–2020, with the State Forests National Forest Holding as beneficiary and support from the Coordination Centre for Environmental Projects as the implementing entity. Implementation targeted lowland forest areas and combined small retention with measures to counteract water erosion. Investments included: constructing, reconstructing, renovating and improving small retention reservoirs and associated infrastructure to enable water extraction for firefighting by State Fire Service units; improving small damming devices to slow surface runoff and protect peat soils; adapting existing drainage systems to provide retention while maintaining passability for fish and other aquatic organisms; stabilising banks and slopes to reduce erosion; and reconstructing or demolishing hydrotechnical structures not suited to floodwaters (such as bridges, culverts and fords). Delivery emphasised many small, simple structures rather than a few large ones, with designs adapted to local natural and landscape conditions and intended to support free movement of aquatic organisms. Environmental effects were to be assessed through post-implementation monitoring of selected adaptation tasks.

Raising the groundwater level stabilizes the humidity conditions in the habitats directly surrounding the small retention facilities. Excluding areas from economic activities contributes to improved soil conditions, and an increase in biodiversity and dead wood resources. Ultimately, this leads to increased carbon accumulation based on natural processes, increasing the resilience of forest ecosystems to climate change. The activities carried out, such as leaving fallen trees or protecting beaver sites that build natural dams also show that sometimes simple measures to slow down the water outflow from forests are enough.