Freshwater glossary

Much of the evapotranspiration from forests falls elsewhere as rain, Ellison et al. (2012), amongst others, have shown that this large scale water pump can be a significant component of the annual precipitation in many continental areas. That is to say, many continental areas would receive a lot less rain if it were not for the mositure returned to the atmosphere by actively growing forests.

A gabion (from Italian gabbione meaning "big cage"; from Italian gabbia and Latin cavea meaning "cage") is a cage, cylinder, or box filled with rocks, concrete, or sometimes sand and soil for use in civil engineering, road building, and military applications.

Green cover (including cover crops or catch crops) refers to crops planted in late summer or autumn, usually on arable land, to protect the soil, which would otherwise lie bare during the winter, against wind and water erosion.ﾠ Green cover crops also improve the structure of the soil, diversify the cropping system, and mitigate the loss of soluble nutrients. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

EU definition: Green Infrastructure is addressing the spatial structure of natural and semi-natural areas but also other environmental features which enable citizens to benefit from its multiple services. The underlying principle of Green Infrastructure is that the same area of land can frequently offer multiple benefits if its ecosystems are in a healthy state. Green Infrastructure investments are generally characterized by a high level of return over time, provide job opportunities, and can be a cost-effective alternative or be complementary to 'grey' infrastructure and intensive land use change. It serves the interests of both people and nature. Clarification points: From the perspective of Natural Water Retention Measures (NWRM), green infrastructure refers to new methods of managing water, favouring as much as possible the restoration of natural ecosystems or at least of their key functionalities in terms of water management. It consists of land management or engineering measures which use vegetation, soils, and other natural materials to restore the natural water retention capacity of the landscape. Green infrastructure measures use natural and man-made materials to enhance or improve longitudinal and lateral hydrological connectivity and natural hydrologic processes, including infiltration and runoff control but also purification processes. Green infrastructure can exist at a range of spatial scales, ranging from the very local, to the scale of a neighbourhood, a city or a whole region. Local scale green infrastructure includes green roofs, permeable pavements and downspout disconnections, all of which can contribute to greater natural infiltration, reduced load on wastewater management systems, and limitations of peak runoff. At the scale of a city or neighbourhood, green infrastructure can support sustainable urban drainage systems that mimic nature by soaking up and storing water or biodiversity promotion with fish ladders. At a regional scale, green infrastructure can include the mosaic of managed semi-natural and natural areas that provides habitat, flood protection, cleaner air, and cleaner water. Thus land management strategies such as afforestation and retention of natural water retaining features in agricultural areas such as riparian buffers, ponds and wetlands can be considered as Green infrastructures designed to manage flood risks in downstream urban areas. One key feature of Green infrastructure is its multi-functionality. The underlying principle of green infrastructure is that the same area of land can offer multiple benefits if the natural or man-made ecosystem is in a socio-ecologically sustainable state. Benefits of green infrastructure include a more natural hydrological cycle and ecosystem services related to biodiversity and human amenity. Green Infrastructure investments are generally characterized by a high level of return over time, provide job opportunities, and can be a cost-effective alternative or be complementary to 'grey' infrastructure and intensive land use change. Green infrastructure serves the interests of both people and nature.

Targeted planting of forests in headwater areas (e.g. with a slope) can help to stabilize hillslopes, thereby reducing erosion and potentially leading to greater water retention in montane areas. Afforestation may have beneficial effects on the hydrograph by reducing peak flows and helping to maintain base flows. The potential for water retention must be balanced against the increased ET and pollutant trapping that may be associated with forests. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

To ease the overall functioning of the river, some hydrographical network elements could be reconnected, including the so-called hydraulic annexes. This will allow for improvement of lateral connectivity, diversifying flows and habitats, but also cleaning the secondary arms that play a key role for retention in high water periods. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Shallow excavations filled with gravel or other material to create temporary storage and to enhance the natural capacity of the ground to infiltrate. Infiltration trenches would typically be used to intercept surface runoff drainage (e.g. drainage from roof or other impervious areas) or to convey water towards a detention pond. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Rainfall that is stored on a vegetation canopy and later evaporated back to the atmosphere.

An enclosed body of water, usually but not necessarily fresh water, from which the sea is excluded.

Lakes are by definition water retention facilities; they store water (for flood control) and provide water for many purposes such as water supply, irrigation, fisheries, tourism, etc.ﾠ In addition, they serve as sinks for carbon storage and provide important habitats for numerous species of plants and animals, including waders.ﾠ In the past, lakes have sometimes been drained to free the land for agriculture purposes, or have simply not been maintained and have silted up.ﾠ Restoring lakes is re-introducing them where they have been in former times or revitalising them. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

It is widely believed that forest soils can function as pollution filters. Afforestation is practiced in rural areas around many large cities as a means of improving the quality of the drinking water supply aquifer by filtering out pollutants. Afforestation may also reduce peak flows and help to maintain base flows. Such afforestation should reduce sediment loadings and may have other benefits including improved biodiversity and recreational value. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Levelling longitudinal barriers allows re-establishing fluvial dynamics and ecological continuity. The aim is to restore the slope and longitudinal profile of the river, to restore natural water flows, to allow for the solid transport (sediment) to take place, toﾠ diversify flows (depth, substrate, speed), diversify habitats and related flora and fauna. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Length of time for which the NWRM may fully operate.

LID is a toolbox of site-scale practices that the site designer and developer can utilize to: manage urban rainfall where it occurs for minimized stormwater concentration and runoff potentially lower short-term and long-term development costs improve water quality enhance natural habitat and flood control improve green space aesthetics and potentially increase property values increase community quality of life and livability There are many practices that are used to support these benefits, including bioretention systems, rain gardens, vegetated rooftops, bioswales, rain barrels, and permeable pavements to name a few. By implementing LID principles and practices, water can be managed in a way that reduces the impact of built areas on the environment while providing numerous additional benefits. This concept is very similar to NWRM in the United States context. It is very connected to Green Infrastructure. See also the link to US EPA green infrastructure website.

From the perspective of Natural Water Retention Measures (NWRM), maintenance is the set of actions or processes that are performed to keep an already existing natural process functioning in the best possible manner. Maintenance can include physical activities, the planning process and communication.

MAR is the purposeful recharge of water to aquifers for subsequent recovery and environmental benefit. Within the context of urban environment, MAR covers the injection and infiltration of captured stormwater ﾖ as such, it is linked to SuDS measures such as rainwater harvesting and infiltration techniques, but worth differentiating as a case where the primary purpose is to increase recharge to aquifers in addition to attenuating surface runoff,Mechanisms used to undertake the recharge should be highlighted. In this respect one can envisage:(i) surface structures to facilitate/augment recharge (such as soakways and infiltration basins);(ii) subsurface indirect recharge - artificial recharge is undertaken through wells drilled within the unsaturated zone;(iii) subsurface direct recharge - artificial recharge is undertaken through wells reaching the saturated zone.The regulatory approach to be adopted for each of the above three mechanisms could differ considerably, due to the fact that the level of natural protection to groundwater is vastly different for each of the mechanisms. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

Meadows are areas or fields whose main vegetation is grass, or other non-woody plants, used for mowing and haying.ﾠ Pastures are grassed or wooded areas, moorland or heathland, generally used for grazing. Due to their rooted soils and their permanent cover, meadows and pastures provide good conditions for the uptake and storage of water during temporary floods. They also protect water quality by trapping sediments and assimilating nutrients. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission

A mulch is a layer of material applied to the surface of an area of soil. Its purpose is any or all of the following:·to conserve moisture·to improve the fertility and health of the soil·to reduce weed growth·to enhance the visual appeal of the areaMulching as NWRM is using organic material (e.g. bark, wood chips, grape pulp, shell nuts, green waste, leftover crops, compost, manure, straw, dry grass, leaves etc.) to cover the surface of the soil. It may be applied to bare soil, or around existing plants. Mulches of manure or compost will be incorporated naturally into the soil by the activity of worms and other organisms. The process is used both in commercial crop production and in gardening, and when applied correctly can dramatically improve the capacity of soil to store water.

Factor of proportionality that shows how much spending in a NWRM may induce direct or indirect changes in macroeconomic variables, such as income, employment, investment, etc. It is another way of referring to wider economic impacts of NWRM.

Natural Water Retention Measures (NWRM) are multi-functional measures that aim to protect and manage water resources and address water-related challenges by restoring or maintaining ecosystems as well as natural features and characteristics of water bodies using natural means and processes. Their main focus is to enhance, as well as preserve, the water retention capacity of aquifers, soil, and ecosystems with a view to improving their status. NWRM have the potential to provide multiple benefits (see benefits table), including the reduction of risk of floods and droughts, water quality improvement, groundwater recharge and habitat improvement. The application of NWRM supports green infrastructure, improves or preserves the quantitative status of surface water and groundwater bodies and can positively affect the chemical and ecological status of water bodies by restoring or enhancing natural functioning of ecosystems and the services they provide (see ecosystem services). The preserved or restored ecosystems can contribute both to climate change adaptation and mitigation.