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).