The monitoring program Ecosystem monitoring in freshwaters (ECOFRESH (= ØKOFERSK)) is a continuation of the three former programs ‘Ecosystem monitoring in freshwaters’ part I, II and III. The program covers both surveillance monitoring in reference lakes in accordance with the Water Framework Directive, and chemical and biological monitoring in a fixed network of acid sensitive lakes. The program is now divided into 6 subprograms, 5 of them geographically divided programs: ØKOFERSK Nord (=North), ØKOFERSK Midt (=Mid), ØKOFERSK Vest (=West), ØKOFERSK Sør (=South) and ØKOFERSK Øst (=East), in addition to a subprogram for monitoring of chemical effects of acidification: ØKOFERSK Sur (=acid).