Manual for constructing water protection structures at ditch network maintenance sites and for water retention in forests

Ditch network maintenance (DNM) is carried out in order to sustain or increase tree growth. DNM includes operations aimed at improving drainage when a high groundwater level impairs tree growth. DNM should be financially justifiable and its harmful impacts on water quality should be minimized. Water protection should be considered when the suitability of DNM is assessed. In the present manual, technical instructions and materials required for constructing water protection structures are presented. The structures in question are fully described in the report “Good practices for ditch network maintenance to protect water quality in the Baltic Sea Region” (Finér et al. 2018). The purpose of these water protection structures is to reduce the transport of suspended solids (SS), nitrogen (N) and phosphorus (P) to downstream watercourses during and after DNM on forest land. In addition to the water protection structures used in DNM, examples of structures used to increase water retention in forest landscapes are briefly presented in the manual. It should be emphasized that the need for retaining water in forests is expected to increase due to climate change.202