The reestablishment of shallow lakes and ponds can be undertaken in various geographic and environmental contexts where suitable conditions exist and where lakes and ponds have been degraded. 

Why

Re-establishment of shallow lakes and ponds addresses different societal challenges, including climate change adaptation and mitigation, disaster risk and preparedness, water management, and biodiversity enhancement. The efficiency will depend on the size of the lakes or ponds re-established and the spatial location of the waterbody relative to land uses in the region.   

Re-establishment of shallow lakes and ponds can protect downstream areas from flooding in periods with high levels of precipitation, because of their capacity to store water, and, consequently, their significance will depend on their size as well as the size of the area adjacent to the waterbody that is allowed to flood.  

Reestablishment of shallow lakes and ponds can stimulate denitrification and help reduce the transport of nitrate to streams and downstream coastal area and reduce CO2 emissions, if applied in low-lying areas with intermediate to high contents of organic carbon. Re-established waterbodies may also enhance carbon dioxide sequestration from the atmosphere thereby restoring natural carbon sinks.  

How

To identify suitable locations for re-establishing shallow lakes and ponds in an area factors like topography, hydrology, soil conditions, vegetation, and existing land use are important to consider.  

Earth-moving equipment can be applied to excavate depressions or basins for the shallow lakes and ponds, where the dimensions and shape of the water bodies should be designed to mimic natural features and create habitat diversity, including shallow areas, littoral zones, and emergent vegetation zones.  

To re-establish shallow lakes and ponds dikes and drainpipes are removed from the area, which causes the area to be filled with water.  

Protect downstream areas from flooding: Reestablished shallow lakes and ponds act as natural buffers against flooding by storing and attenuating stormwater runoff. They can retain excess water during heavy rainfall events, reduce peak flows downstream and mitigate flood risk in flood prone area including critical infrastructure.   

Water quality improvement: Reestablished shallow lakes and ponds play a vital role in improving water quality by filtering pollutants and trapping sediment. Furthermore, if the water entering the re-established waterbody is rich in nitrate for example because it comes from disconnected drainpipes or ditches carrying runoff from agricultural land, then shallow waterbodies may also play an important role in lowering the transport of nitrogen to downstream coastal areas. 

Reestablished lakes and ponds play a role in carbon sequestration as they act as carbon sinks, capturing and storing carbon dioxide from the atmosphere, which helps mitigate climate change and reduce greenhouse gas emissions. 

Climate mitigation: Reestablished shallow lakes and ponds can also contribute to reduce CO2 emission, primarily in areas where organic soil contents are intermediate to high (>6%). This creates oxygen-free conditions that slow down the decomposition of the organic matter in the soil. Lakes can also help buffering water supply to streams and other water-dependent ecosystems that may otherwise suffer desiccation during summer by allowing water accumulated in the lakes during winter to enter these ecosystems. 

Potential side effects 

Methane emission: There is a high risk of methane emissions in areas with standing water. Anaerobic conditions create favourable conditions for the formation of methane gas through anaerobic decomposition and, as methane is a greenhouse gas, just like CO₂, methane emission may counteract the positive effect of less CO₂ emission. This side effect varies significantly with water quality, and water quality management targeting internal eutrophication has the potential to lower CH₄ emissions. 

ATTENTION

Re-establishement of shallow lakes and ponds can provide many different ecosystem service benefits. To ensure biodiversity net gains within the re-established waterbody, it is important to be aware that high inputs of nutrients can be critical for the establishment of many plant species both within the waterbody and in the littoral and emergent vegetation zones. Therefore, targets for biodiversity net gain should reflect the type of water that enter the re-established water body. If the water entering the re-established water body is rich in nutrients, for example from closed drainage pipes and/or ditches, algae may be dominant in the water column. While eutrophic water bodies may pose challenges for some bird species due to degraded water quality and habitat conditions, such waterbodies can still support a varied birdlife, especially if they offer a range of habitat features and are managed to enhance biodiversity. Additionally, efforts to improve water quality can further support the development of a diverse bird community over time.  

Costs

Implementation (manpower, technology, costs of buying land etc.), operational costs, maintenance and monitoring costs. This text should be qualitative rather than quantitative.