AfforestationAfforestation is the process of planting trees, either to replace those removed during forest harvesting or as a means of land use conversion. Afforestation is part of several natural water retention measures as it can contribute to a more natural and sustainable hydrologic cycle.
Agricultural practiceAgronomic practices which have the primary purpose of improvements to agriculture can, in some cases, contribute to the functioning of natural water retention measures. As such, they integrate sustainable and natural water management into current practices.
Ancillary benefitAdditional or subsidiary, positive impact (in terms of social welfare). As in the case of avoided costs or damages, an ancillary benefit is an indirect one. NWRM come along with other important impacts in terms of biodiversity, amenity, etc. that are exclusive. These are not linked to the genuine objectives of River Basin Management Plans but rather may arise if the objectives of these plans are met by adding NWRM to the Programmes of Measures.
Appropriate design of roads and stream crossingsAppropriately designed roads and stream crossings can minimize the likelihood of erosion and sediment production that can be associated with forestry activities including final harvest. Poorly designed or built roads and stream crossings can cause some of the most negative effects of forestry on the landscape. Well-designed roads follow the contours of the landscape. Roads which run up and down (instead of across) hills can act as channels which focus runoff and can lead to increased erosion. Properly designed stream crossings permit the free movement of fish and aquatic invertebrates and will not restrict peak flows. Ensuring that stream crossings do not restrict peak flows will help to reduce localized flooding and can ultimately be more cost effective as they will not need to be rebuilt following high flow events - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Artificial groundwater recharge (AGR)AGR stores large quantities of water in underground aquifers to increase the quantity of groundwater in times of shortage.ᅠ It results in a lowering of run-off from surrounding land, and in an enhanced natural condition of aquifers and water availability.ᅠ The natural cleaning process of water percolating through the soils when entering the AGR improves water quality. 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
Avoided costEquivalent to an indirect benefit; financial outlays, negative impacts or welfare losses on anyone which are eluded by choosing one specific course of action among different alternatives. Some natural water retention measures (NWRM) may protect rivers and freshwater sources thus reducing other protection costs, increasing riversメ natural assimilation capacity and making other quality measures redundant. For example, mulching and other NRWM may reduce erosion and enlarge the lifespan of reservoirs while reducing their maintenance costs, etc. These benefits are context-based (and potentially site-specific) and therefore often difficult to identify and quantify. Valuation alternatives range from the estimation of production losses to the cost of defensive and replacement measures (i.e. averting behaviour).
BankThe sloping side of any hollow in the ground, especially when bordering a river. (Source: CED)
Basic measureBasic measures are the minimum requirements to be complied with and shall consist of: (a) those measures required to implement Community legislation for the protection of water, including measures required under the legislation specified in Article 10 and in part A of Annex VI; (b) measures deemed appropriate for the purposes of Article 9; (c) measures to promote an efficient and sustainable water use in order to avoid compromising the achievement of the objectives specified in Article 4; (d) measures to meet the requirements of Article 7, including measures to safeguard water quality in order to reduce the level of purification treatment required for the production of drinking water; (e) controls over the abstraction of fresh surface water and groundwater, and impoundment of fresh surface water, including a register or registers of water abstractions and a requirement of prior authorisation for abstraction and impoundment. These controls shall be periodically reviewed and, where necessary, updated. Member States can exempt from these controls, abstractions or impoundments which have no significant impact on water status; (f) controls, including a requirement for prior authorisation of artificial recharge or augmentation of groundwater bodies. The water used may be derived from any surface water or groundwater, provided that the use of the source does not compromise the achievement of the environmental objectives established for the source or the recharged or augmented body of groundwater. These controls shall be periodically reviewed and, where necessary, updated; (g) for point source discharges liable to cause pollution, a requirement for prior regulation, such as a prohibition on the entry of pollutants into water, or for prior authorisation, or registration based on general binding rules, laying down emission controls for the pollutants concerned, including controls in accordance with Articles 10 and 16. These controls shall be periodically reviewed and, where necessary, updated; (h) for diffuse sources liable to cause pollution, measures to prevent or control the input of pollutants. Controls may take the form of a requirement for prior regulation, such as a prohibition on the entry of pollutants into water, prior authorisation or registration based on general binding rules where such a requirement is not otherwise provided for under Community legislation. These controls shall be periodically reviewed and, where necessary, updated;
Basins and pondsBasins and ponds store surface run-off.ᅠ Detention basins are free from water in dry weather flow conditions but ponds (e.g., retention ponds, flood storage reservoirs, shallow impoundments) contain water in dry weather, and are designed to hold more when it rains. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Biophysical environmentThe biophysical environment is the biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development and evolution. The biophysical environment can vary in scale from microscopic to global in extent. It can also be subdivided according to its attributes. Examples include the marine environment, the atmospheric environment and the terrestrial environment. The number of biophysical environments is countless, given that each living organism has its own environment.The symbiosis between the physical environment and the biological life forms within the environment includes all variables that comprise the Earth’s biosphere. The  biophysical  environment  can  be  divided  into  two  categories:  the  natural  environment  and  the built environment with some overlap between the two. Following the industrial revolution the built environment has become an increasingly significant part of the Earth's environment.  The scope of the biophysical environment is all that contained in the biosphere, which is that part of the Earth in which all life occurs.When narrowed down to the aquatic environment, and particularly in the context of the Water Framework Directive, these are often  referred  to  as  water  quality,  water  quantity  and  hydromorphology.  
Biophysical parameterA biophysical parameter is a measurable characteristic that can help in defining a particular system. It can cover individual substances, groups of substances or be defined by its measurement method like turbidity or the mesurement of oxygen consumption like BOD5 or COD. It is generally expressed by a value and its unit.
Buffer strips and shelter beltsBuffer strips are areas of natural vegetation cover (grass, bushes or trees) at the margin of fields, arable land, transport infrastructures and water courses. They can have several different configurations of vegetation found on them varying from simply grass to combinations of grass, trees, and shrubs.ᅠ Due to their permanent vegetation, buffer strips offer good conditions for effective water infiltration and slowing surface flow; they therefore promote the natural retention of water. They can also significantly reduce the amount of suspended solids, nitrates and phosphates originating from agricultural run-off. Buffer strips can be sited in riparian zones, or away from water bodies as field margins, headlands or within fields (e.g. beetle banks). Hedges across long, steep slopes may reduce soil erosion as they intercept and slow surface run-off water before it builds into damaging flow, particularly where there is a margin or buffer strip alongside. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Channels and Rills'Hard-edged' conveyance channels to move water between components in a SuDS 'train'.ᅠ Typically narrower than swales, but may also include vegetated aspects. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Coarse woody debrisCoarse woody debris is a key stream habitat feature used by fish and other organisms. Coarse woody debris can also help to lower flow velocity in streams. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Continuous Cover forestryContinuous cover forestry (CCF) is a broad term encompassing a wide variety of forest management practices. One key feature of is that biomass removal is based either on small clearcuts or selective harvesting. Smaller clearcuts may create less hydrological disturbance but some of the filtration benefits associated with forest soils may be lost as a result of the greater driving and road maintenance needed for continuous harvesting. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Controlled Traffic FarmingControlled traffic farming is a system which confines all machinery loads to the least possible area of permanent traffic lanes. Current farming systems allow machines to run at random over the land, compacting around 75% of the area within one season and at least the whole area by the second season. Soils donメt recover quickly, taking as much as a few years. A proper CTF system on the other hand can reduce tracking to just 15% and this is always in the same place. CTF is a tool; it does not include a prescription for tillage although most growers adopting CTF use little or none because soil structure does not need to be repaired. The permanent traffic lanes are normally parallel to each other and this is the most efficient way of achieving CTF, but the definition does not preclude tracking at an angle. The permanent traffic lanes may be cropped or non-cropped depending on a wide range of variables and local constraints. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Cost-Benefit AnalysisA framework of analysis based on economic rationality (within a number of constraints one will always try to make that decision that increases her individual welfare) and founded on welfare economics. CBA compares costs and benefits of different alternatives and provides rational criteria for decision-making.ᅠ CBA is a critical input for some decisions but does not replace decisions themselves (i.e. its result is not a binding one). CBA quantifies in monetary terms and compares the pros and cons of any initiative, including items for which the market does not provide a satisfactory measure of economic value. CBA yields profitability indicators, financial, economic or social, on the basis of information throughout the lifespan of the project. It is to be used when the objectives of different NWRM or Programmes of Measures are not the same, that is to say, when what is at stake is not just a set of alternative measures themselves but also different collective aims. ᅠ
Cost-effectiveness AnalysisAnalytical tool or appraisal technique that assesses the costs of alternative ways of producing the same output or alike. It ranks alternative measures on the basis of their costs and effectiveness, where the most cost-effective measure gets the highest ranking. Since CEA is suggested for comparative analyses, costs to be collected should include those that are not site-specific.
Crop rotationCrop rotation is the practice of growing a series of dissimilar/different types of crops in the same area in sequential seasons. It gives various benefits to the soil. A traditional element of crop rotation is the replenishment of nitrogen through the use of green manure in sequence with cereals and other crops. Crop rotation also mitigates the build-up of pathogens and pests that often occurs when one species is continuously cropped, and can also improve soil structure and fertility by alternating deep-rooted and shallow-rooted plants. Can be used in combination with other measures where these are compatible with crop choice. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Detention/Infiltration BasinsVegetated depressions designed to store runoff on the surface and allow it to gradually infiltrate into soil. Infiltration basins are dry, except in periods of heavy rainfall, and may serve to other functions (e.g. recreation). They provide flow control through attenuation of runoff at the end of SuDS ムchainsメ.ᅠ Basins may also act as モbioretention areasヤ of shallow landscaped depressions, typically under-drained, relying on engineered soils, vegetation and filtration to reduce runoff and remove pollution. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Downspout disconnectionDownspout disconnection involves theᅠrerouting of rooftop drainage pipes from the storm sewer systemᅠtoᅠrain barrels,ᅠcisterns,ᅠor permeable areas instead of the storm sewer.ᅠThis reduces the loading of rainwater on the storm sewer systemᅠ, and can have great benefits in cities with combined sewer systems. ᅠDownspout disconnectionᅠstores stormwater and/or allows stormwater to infiltrate into the soil, thus contributing to the natural water retention calacity of the landcape.
Early sowingEarly sowing refers to sowing up to six weeks before the normal sowing season.ᅠ This allows for an earlier and quicker development of crops and of a root network that leads to soil protection.ᅠ The period in which the soil lies bare is shorter and, therefore, erosion and run-off are less significant and water infiltration is improved.ᅠ Early sowing can also help to mitigate the extreme ETP rates typical of Mediterranean summers.ᅠ However, early sown plants are frost sensitive; therefore farmers run the risk of losing the crops because of the low temperatures.ᅠ In northern countries, temperature in spring (March) can be adequate but the risk of frost is still serious until May.ᅠ Therefore, early sowing requires specific tools (plastic tunnel covers, onsite green house, etc.) and cannot be applied by any farmers for any crops. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Economic costSacrifice associated to the use of available resources to one means instead of another (so that any economic cost is indeed an opportunity cost) or of following one course of action instead of the best available alternative. As applied to NWRM, it refers to those negative impacts in terms of welfare, either direct or indirect, that may be linked to the implementation of any measure. The difference between explicit and implicit costs depends on whether there is an unequivocal monetary payment (or at least one which is straightforward to infer) or not. The term モdirect (economic) costヤ does actually refer to those costs that fall directly on the promoter of the NWRM. Hence, as opposed to direct costs, indirect costs are those incurred by others (those who are not under the direct scope of the NWRM implementation).
Elimination of riverbank protectionThe suppression of lateral constraints consists in removing some bank protection in order to enhance lateral connection of the river, diversifying flows (depth, substrate, speed), diversify habitats but also capping floods in the mainstream. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Environmental costNegative impacts connected with the actual or potential degradation of natural assets or environmental quality due to economic activities.
Equivalent Annual CostThe cost per year of implementing a NWRM over its entire lifespan. EAC is used when comparing NWRMs of unequal lifespans. It is estimated through listing all capital expenditures and when they are incurred; calculating the net present value of expenditures, once discounted; and converting this net present value into an annuity
ErosionThe general process or the group of processes whereby the materials of Earth's crust are loosened , dissolved, or worn away and simultaneously moved from one place to another, by natural processes, which include weathering, solution, corrosion, and transportation, but usually exclude mass wasting. For the case of NWRM, erosion refers mainly to soil erosion due to surface run-off. The eroded material is generally called sediment. (Source: adapted from Wikipedia and GEMET)
Externality(either positive or negative). Third-party effect or welfare impact, which is both unilateral (i.e. one cannot decide neither whether to suffer it or not nor how much impact to bear), and non-compensated. In other words, an externality stemming from the implementation of a NWRM is a cost (if negative) or a benefit (if positive), which is not directly reflected in the direct costs or benefits of the NWRM but are one of its outcomes. It is a welfare variation expressed in monetary units.
Filter StripsGently sloping vegetated strips of land that provide opportunities for slow conveyance and infiltration. Designed to accept runoff as overland flow from upstream and to slow the progress of this runoff. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Financial costThe (monetary) value of resources deployed for the implementation of any NWRM, which includes upfront capital expenditures, either from new investments or the replacement of assets in past investments; depreciation allowances (annualised cost or replacing the accounting value of existing assets in the future); operating expenditures (those incurred to keep the NWRM running in an efficient manner); maintenance expenditures (for preserving existing or new assets in good functioning order throughout their useful life); and decommissioning costs (those incurred at the end of the lifecycle of the NWRM).
FloodplainA floodplain isᅠan area of land adjacent to a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls which provides space for the retention of flood and rainwater.ᅠ It experiences flooding during periods of high discharge. It includes the floodway, which consists of the stream channel and adjacent areas that actively carry flood flows downstream, and the flood fringe, which are areas inundated by the flood, but which do not experience a strong current. Floodplain soils are generally very fertile and they have often been dried-out to be used as agricultural land. Floodplains have also been separated from the river by dikes, berms or other structures designed to control the flow of the river. Nowadays, the objective is to restore them, their retention capacity and ecosystem functions by reconnecting them to the river. Example of action that can be done on floodplains: hedges to break flood streams, e.g. hedges perpendicular to the river flow that are planted in the restored floodplain to slow down floods. In other words, a floodplain is an area near a river or a stream which floods when the water level reaches flood stage. - Based on Stella definition and Wikipedia, adapted by NWRM project experts
Forest HarvestingForest harvesting can cause severe disruptions to the hydrologic cycle. Clearcut areas are often subject to localized flooding due to reductions in evapotranspiration caused by removal of trees. Roads and other infrastructure needed to support forest harvesting can also be significant sources of sediment to surface waters. However, negative effects can be minimized when forest harvesting is performed in a water-sensitive manner and measures are taken to maintain the natural hydrological functioning of the landscape.
Forests as large-scale water pumpsMuch 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.
GabionA 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 coverGreen 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
Green infrastructureEU 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.
Green roofSystems to cover the roof of a building or structure with vegetation cover and/or landscaping.ᅠ Green roofs are designed to intercept and retain precipitation, reducing the volume of runoff and attenuating peak flows.
Grey infrastructureFrom the perspective of Natural Water Retention Measures (NWRM), grey infrastructure usually refers to the traditional methods of managing water, using man-made, constructed assets, most often water tight and designed to avoid any type of ecosystem to grow on it. Modern grey infrastructure such as permeable pavements and some roof water retention systems mimic the natural water retention capacity of the landscape and help to restore more natural patterns of run-off and infiltration. It includes channels, pipes, sewers and sewage treatment works, ditches, dikes, dams... Grey infrastructure is so-called because it is often constructed of concrete. Unlike green infrastructure, grey infrastructure typically does not deliver multiple benefits. Grey infrastructure such as sewers and sewage treatment works are needed in urban areas but their effectiveness can be enhanced by green engineering measures which help to restore the natural water retention capacity of the landscape.
Headwater areasTargeted 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
Hydraulic annexesTo 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
InfiltrationThe penetration of water into the soil from the surface.
Infiltration CapacityThe maximum rate at which water can infiltrate into the soil from the surface.
Infiltration TrenchesShallow 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
Interception Rainfall that is stored on a vegetation canopy and later evaporated back to the atmosphere.
IntercroppingIntercropping is the practice of growing two or more crops in proximity. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop. Examples of intercropping strategies are planting a deep-rooted crop with a shallow-rooted crop, or planting a tall crop with a shorter crop that requires partial shade. Numerous types of intercropping, all of which vary the temporal and spatial mixture to some degree, have been identified: mixed intercropping, row cropping, relay cropping, etc. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
LakeAn enclosed body of water, usually but not necessarily fresh water, from which the sea is excluded. (Source: WHIT)
Lake restorationLakes 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
Land use conversionIt 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
LeachingThe process by which nutrients and other chemicals are washed out of the soil by percolating water. Nitrate fertilisers, for example, are washed out of the soil because of their high solubility. They eventually find their way into watercourses or groundwater causing pollution.
Levelling of dams/ longitudinal barriersLevelling 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
LifespanLength of time for which the NWRM may fully operate.
Low Impact DevelopmentLID 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 runoffpotentially lower short-term and long-term development costsimprove water qualityenhance natural habitat and flood controlimprove green space aesthetics and potentially increase property valuesincrease community quality of life and livabilityThere 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. (source: LID symposium).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.
MacroporesLarge pores in the soil that may form important pathways for infiltration and redistribution of water bypassing the soil matrix as a preferential flow. May result from soil cracking and ped formation, root channels and animal burrows. May be important in transport of contaminants.
MaintenanceFrom 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.
Managed Aquifer Recharge (MAR)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 and pasturesMeadows 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
MulchingA 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.
Multiplier effectFactor 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 bank stabilisationIn the past, various activities were undertaken to straighten rivers, such as the stabilisation of river banks with concrete or other types of retention walls.ᅠ Such actions limited riversメ natural movements, leading to degradation of the river, increased water flow, increased erosion and decreased biodiversity.ᅠ Natural bank stabilisation reverses such activities, allowing rivers to move more freely.ᅠ Where bank stabilisation is nevertheless necessary, such as in residential areas, natural materials such as roots or gravel can be used.ᅠ Natural materials are preferable as they allow water to infiltrate into the bank.ᅠ They also provide better living conditions for aquatic fauna. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Natural Water Retention MeasureNatural 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.
Nature Based SolutionNature-based solutions aim to help societies address a variety of environmental, social and economic challenges in sustainable ways. They are actions which are inspired by, supported by or copied from nature. Some involve using and enhancing existing natural solutions to challenges, while others are exploring more novel solutions, for example mimicking how non-human organisms and communities cope with environmental extremes. Nature-based solutions use the features and complex system processes of nature, such as its ability to store carbon and regulate water flow, in order to achieve desired outcomes, such as reduced disaster risk, improved human well-being and socially inclusive green growth. Maintaining and enhancing natural capital, therefore, is of crucial importance, as it forms the basis for implementing solutions. These nature-based solutions ideally are energy and resource-efficient, and resilient to change, but to be successful they must be adapted to local conditions.
NitrateNitrate, NO-3, is the main nitrogen containing anion occurring in the soil. It is very soluble and moves freely in water through the soil profile. Nitrate in water is a pollutant above certain concentrations and can be a danger to human health. The main source of nitrate in water is agriculture although sewage discharges can also be an important factor.
Nitrate leachingThe 1980 EC Drinking Water Directive set a maximum of 50 mg/l of nitrate in drinking water (equivalent to 11.3 mg/l nitrate-nitrogen). An increasing number of water sources currently exceed this limit. Agriculture is the main source of nitrate in drinking water where nitrate, having a high solubility, washes out of the soil and gradually, often over many years, reaches underground water sources. Losses of nitrate by leaching depend on soil type and rainfall. The lightest arable soils only retain about 80 mm of water per metre depth; so nitrate in these, and the shallow soils which are so extensive in the UK are much more easily leached than nitrate in deep clay or silt soils which may retain more than 200 mm of water per metre. The amount of rain which is in excess of evaporation and crop transpiration and which therefore causes leaching, varies from about 150 mm per annum in the East to more than 300 mm per annum in some western and northern arable regions. In some grassland regions more than 1000 mm per annum is not unusual.
No tillageTillage is a mechanical modification of the soil.ᅠ Intensive tillage can disturb the soil structure, thus increasing erosion, decreasing water retention capacity, reducing soil organic matter through the compaction and transformation of pores. No-till farming (also called zero tillage or direct drilling) is a way of growing crops or pasture from year to year without disturbing the soil through tillage. No-till is an agricultural technique which increases the amount of water that infiltrates into the soil and increases organic matter retention and cycling of nutrients in the soil. In many agricultural regions it can eliminate soil erosion. The most powerful benefit of no-tillage is improvement in soil biological fertility, making soils more resilient. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Opportunity costValue of those alternatives foregone when implementing a NWRM.
Overland flow areas in peatland forestsDitch blocking in managed peatland forests can be used to slow water and trap sediment after forest harvesting. The ditches can be made of wood logs or gabions, for example. - Elaborated by NWRM project experts and validated by the European Commission
Peak flow control structuresEngineered ponds in peatlands that have been ditched to enhance forest production have the potential to retain water in the landscape and trap sediment without adversely affecting tree growth. Such measures have the potential to limit hydrograph peaks and potentially reduce flooding associated with snowmelt. - Elaborated by NWRM project experts and validated by the European Commission
Permeable paving and other permeable surfacesPervious surfaces (either porous or permeable) like permeable paving designed to allow rainwater to infiltrate through the surface and into underlying layers (soils and aquifers), or broader use of permeable areas to promote greater infiltration. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
PhosphorusPhosphates from agriculture are an important contributor to phosphorus loading on water bodies. Phosphorus is considered to be a limiting factor in the process of eutrophication that can generally be regarded as the enrichment of surface waters by nutrients which causes overgrowth of algae and weeds. The result is deoxygenation of waters that can kill fish and other aquatic life. Algae growth can also be a hazard to human health.
Preferential flow Local concentrations of flow in the soil that may be due to the effects of macropores, local variations in hydraulic properties or fingering of a wetting front moving into the soil profile. May lead to rapid and deep infiltration of water bypassing much of the soil matrix (see also Macropores)
Rain GardensSmall-scale depressions used for storage and infiltration, typically at a property-level and close to buildings (e.g. to infiltrate roof drainage at a property level). - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Rainwater HarvestingCollecting and storing rainwater for subsequent use ヨ for example, using water butts or larger storage tanks. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
ReconnectionFrom the perspective of natural water retention measures (NWRM), reconnection is the process of improving hydrological connection in the landscape, both through linking water bodies and through improving the connectivity between rivers and their adjacent floodplains. Reconnection can make use of historical and currently water channels to restore previously existing hydrological connectivity and functioning.
Reduced/Conservation tillageConservation tillage leaves at least 30% of crop residue on the soil surface, or at least 1,100ᅠkg/ha of small grain residue on the surface during the critical soil erosion period. This slows water movement, which reduces the amount of soil erosion. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Reduced stocking densityReduced stocking density will limit soil compaction, thereby facilitating more rapid infiltration during precipitation events and potentially reducing peak flows and sediment runoff. - Elaborated by NWRM project experts and validated by the European Commission
Re-meanderingIn the past, rivers have been straightened by cutting off meanders (historically, many rivers in northern and western Europe have been straightened and channelized to facilitate log floating and/or speed up the drainage of water and control/limit the river bed movements).ᅠ Re-meandering is bringing a river back closer to its naturally meandering state by creating a new meandering course and by reconnecting cut-off meanders.ᅠ Re-meandering slows down the flow of a river.ᅠ The new form of the river channel creates new flow conditions and very often also has an impact on sedimentation.ᅠ The newly created or reconnected meanders also provide habitats for a wide range of aquatic and land species of plants and animals. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
RenaturationA process of returning natural ecosystems or habitats to their original structure and species composition. Renaturation requires a detailed knowledge of the original species, ecosystem functions and interacting processes involved. (Source: GEMET, adapted from DUNSTE)
Reservoir catchmentAfforestation of reservoir catchments can have multiple benefits. It can reduce sediment inputs from the catchment, lengthening the life of the reservoir, and may also have beneficial effects on water quality in some cases when peatlands are afforested. Afforestation can reduce peak flows and help to maintain base flows. The benefits of afforestation must be balanced against the potential for increased evapotranspiration from a rapidly growing forest. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Resource costThe cost linked the economic or relative scarcity of water once it is used.
RestorationRestoration is a management action or set of actions with the aim of restoring natural hydrologic functioning ᅠin the landscape. Restoration of natural functioning can contribute to an environmental balance in water management. NWRM implementation can either be an enhancement/improvement of the natural hydrologic functioning ᅠin the landscape or a restoration action.
Retention PondsPonds or pools with additional storage capacity to attenuate surface runoff during rainfall events.ᅠ Retention time of runoff can provide the capacity to remove pollutants through sedimentation and opportunity for biological uptake of nutrients. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Revitalisation of flowing watersIn the past, rivers flows have been modified through channelisation, embankments or modification of river beds. Those modifications were aiming at flood prevention or supporting changes of agricultural practices for example. This has led to uniformed flows in the rivers and often having effect on the water time transfers. Current practices for revitalisation of flowing waters are trying to create the conditions for diversifying the water flows, inducing more diversity in habitats for fauna but also increasing the water time transfers in order to prevent flash floods in the downstream areas for example. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Riparian buffersPlanting and maintaining tree cover in near-stream areas can have multiple benefits including erosion and nutrient leaching control. They will also slow the stream velocity during high flow flood events and may have beneficial effects on stream temperature. Maintaining treed forest buffers during clearcutting can help minimizing the adverse effects of forestry on water quality and may have additional biodiversity benefits. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Riparian zone1) Terrestrial areas where the vegetation complex and microclimate are products of the combined pressure and influence of perennial and/or intermittent water... and soils that exhibit some wetness characteristics. 2) Zone situated on the bank of a water course such as a river or stream. (Source: DUNSTE / GILP96)
RiverbedThe channel containing or formerly containing the water of a river. (Source: BJGEO)
Riverbed (alluvial mattress)The reconstitution of the alluvial mattress consists in leveling-up the river bed and/or reactivating the bank erosion in order to stop the incision of the river bed. It can allow better connection with side arms, level-up the water level at low flow periods, diversifying flows (depth, substrate, speed), diversify habitats and increase retention times. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Sediment capture pondsSediment capture ponds are widely used to "slow down" water being drained from boreal forests. The main function of the sediment capture ponds is to remove prevent pollution of receiving waters downstream of a forest by removing suspended sediment and associated pollutants. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
SoakawaysExcavations, typically filled with gravel, designed to store water and allow it to infiltrate into underlying soils or aquifers.ᅠ Soakaways would typically receive point-source inflow (e.g. from roof drainage).ᅠᅠ - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Soil ConservationThe management of land to minimise soil erosion to maintain soil and water resources, and provide sustainable benefits in the long term.
Strip croppingStrip cropping is a method of farming used when a slope is too steep or too long, or otherwise, when one does not have an alternative method of preventing soil erosion. It alternates strips of closely sown crops such as hay, wheat, or other small grains with strips of row crops, such as corn, soybeans, cotton, or sugar beets. Strip cropping helps to stop soil erosion by creating natural dams for water, helping to preserve the strength of the soil. Certain layers of plants will absorb minerals and water from the soil more effectively than others. When water reaches the weaker soil that lacks the minerals needed to make it stronger, it normally washes it away. When strips of soil are strong enough to slow down water from moving through them, the weaker soil can't wash away like it normally would. Because of this, farmland stays fertile much longer. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
SubsoilingOn heavy or poorly structured soils it is occasionally necessary to loosen the soil to a greater depth than that reached by normal cultivations, in order to improve drainage and root penetration. Subsoiling machines (subsoilers) for this purpose can operate at depths from 300-600 mm and at spacing as close as 1 metre. Subsoiling may be used to counteract effects of soil smearing and compaction resulting from handling of soils in wet conditions.
Sunk costThose expenditures that, once committed, cannot be (easily) recovered. These costs arise because some activities require specialized assets that cannot be readily diverted to other uses.
Supplementary measure"Supplementary" measures are those measures designed and implemented in addition to the basic measures, with the aim of achieving the objectives established pursuant to Article 4 of the WFD. Part B of Annex VI contains a non-exclusive list of such measures. Member States may also adopt further supplementary measures in order to provide for additional protection or improvement of the waters covered by this Directive, including in implementation of the relevant international agreements referred to in Article 1.
Surface RunoffSurface runoff can be described as water flowing over soil, vegetation or other ground cover instead of infiltrating to the underlying soil. Surface runoff may be caused by imperviousness of the underlying material, or because the underlying material is already being saturated, i.e. at capacity. The quantity of water during storm events (and/or runoff from adjacent impervious surfaces) may exceed the infiltration capacity of the soil and receiving waters resulting in increased flood risk. The speed at which liquid soaks into the soil is important in working out the risk of runoff.ᅠ Run-off can contribute to on-site and off-site problems via leaching and erosion. This includes: - losses of pesticides, fertilisers or soil, - pollution of receiving water if the run-off water is contaminated with pesticides, fertilisers or sediment, - other biophysical impacts on the aquatic environment like excessive sedimentation and clogging, or high concentrations of suspended solid which in turn cause cloudiness of the water affecting the quantity of sunlight that infiltrates the water.
Suspended SedimentThe solid particles, suspended within the water column, which the water is carrying. Includes soil particles and organic material derived from living thing. Can be measured by filtering the water and accurately weighing the dried residue to give a figure in milligrams per litre.
Sustainable Drainage Systems"Approaches to manage surface water that take account of water quantity (flooding), water quality (pollution)ᅠand amenity issues are collectively referred to as Sustainable Drainage Systems (SuDS). SuDS mimic nature and typically manage rainfall close to where it falls. SuDS can be designed to slow water down (attenuate) before it entersᅠstreams, rivers and other watercourses, they provide areas to store water in natural contours and can be used to allow water to soak (infiltrate) into the ground or evaporated from surface water and lost or transpired from vegetation (known as evapotranspiration)." (Source: susdrain)
Sustainable Urban Drainage SystemsSustainable Urban Drainage Systems (or SUDS) are a sequence of water management practices, green infrastructures and measures designed to drain surface water in a manner that mimics the natural hydrologic cycle and will provide a more sustainable approach to rainwater management than what has been the conventional grey infrastructure practice of routing run-off through a pipe to a receiving watercourse.
SwalesShallow, broad and vegetated channels designed to store and/or convey runoff. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Targeted planting for "catching" precipitationThere is some evidence that planting trees on some Mediterranean hillslopes can assist in cloud formation and precipitation. The forests assist in "trapping" rising air and condensing atmospheric water vapour. This work has been pursued by Milan Milan, amongst others. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Temporary tributaries flowTemporary streams are of particular importance when it comes to water storage and time retention especially in flash flood prone areas. Some measures can be directly implemented in order to ensure their proper functioning. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Traditional terracingTraditional terraces consist of nearly level platforms built along contour lines of slopes, mostly sustained by stone walls, used for farming on hilly terrain.ᅠ When properly built and well maintained, terraces can reduce erosion and surface run-off by slowing rainwater to a non-erosive velocity.ᅠ So-called traditional terracing involves less disturbance of the terrain than modern terracing, as it does not involve significant levelling or cutting using heavy machinery.ᅠ - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Transaction costEfforts (either monetary outlays or consumption of any other resources, such as time) of administering, monitoring, and enforcing a NWRM. Policy-making involves political costs that are absent in private exchanges.
Trees in urban areasUrban planning that incorporates trees can have multiple benefits. Trees in urban areas have multiple benefits including increased infiltration and other benefits including shade and amenity value. - Elaborated by NWRM project experts, validated by th European Commission
TurbidityA measure of how much suspended sediment is in the water. It is generally monitored in a stream or lake. The higher the turbidity the ムdirtierメ the water and the less light will penetrate into the water.
Urban forests parksUrban forest parks or protected areas provide multiple benefits including increased water infiltration, pollutant filtration, reductions in peak flow and maintenance of base flows. Urban forests also have many other aesthetic, biodiversity and quality of life benefits. - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
Urban PlanningWithin the framework of natural water retention measures (NWRM), urban planning refers to the application of the "Grey to Green" principle within cities. The specific focus of urban planning for NWRM is to achieve sustainable water management by mimicking natural functions and processes in the urban environment.
Water retentionWater retention covers a wide set of mechanisms (see synthesis document n°1) the effect of which are to increase the capture of water by aquifers, soil, and aquatic and water dependent ecosystems. More precisely it refers to capabilities of catchments (including wetlands, rivers and floodplains but also other land areas) to hold or retain as much water as possible during periods of abundant or even excessive precipitation, so that water is available for use during dry periods and runoff peaks are minimized.
"Water sensitive" driving"Water sensitive driving" requires an awareness of the wet areas (mires, peatlands, etc.) in the landscape and an ability to avoid them while conducting forestry operations. Water sensitive driving is focussed primarily on minimizing water quality impacts of forestry including nutrient leakage and an increased potential for methylmercury formation.
Wetland (measure)Wetlands restoration and creation can involve: technical, spatially large-scale measures (including the installation of ditches for rewetting or the cutback of dykes to enable flooding); technical small-scale measures such as clearing trees; as well as changes in land-use and agricultural measures, such as adapting cultivation practices in wetland areas.ᅠ Wetland restoration can improve the hydrological regime of degraded wetlands and generally enhance habitat quality. (Creating artificial or constructed wetlands in urban areas can also contribute to flood attenuation, water quality improvement and habitat and landscape enhancement). - Based on Stella definitions, adapted by NWRM project experts and validated by the European Commission
WetlandsAreas that are inundated by surface or ground water with frequency sufficient to support a prevalence of vegetative or aquatic life that requires saturated or seasonally saturated soil conditions for growth or reproduction. Wetlands provide both stormwater attenuation and treatment, comprising shallow ponds and marshy areas covered in aquatic vegetation.ᅠ Wetlands detain flows for an extended period to allow sediments to settle and to remove contaminants.ᅠ They also provide runoff attenuation and can provide significant ecological benefits.