Sacrifice 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).

Appropriately 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

Agronomic 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.

Forest 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.

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

An enclosed body of water, usually but not necessarily fresh water, from which the sea is excluded. (Source: WHIT)

Length of time for which the NWRM may fully operate.

Negative impacts connected with the actual or potential degradation of natural assets or environmental quality due to economic activities.

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.

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