Estimation of environmental flows in semi-natural lowland rivers - the Narew basin case study

Abstract

This paper discusses a new environmental flow method based on the adapted building block approach. A four-step procedure is outlined in this paper: (1) selecting biota of interest and organizing a team of specialists; (2) selecting river reaches of interest; (3) defining flow requirements of selected biota; (4) defining environmental flow indicators. The focus is placed on two elements of river and wetland ecosystems: fish and floodplain wetland vegetation. The method is applied to identify changes in the environmental flow indicators between 1976-83 (“past”) and 2001-08 (“present”) in 16 selected river reaches of the Narew basin, a large semi-natural lowland catchment situated in northeastern Poland. The results indicate that hydrological conditions for fish and floodplain wetland vegetation were significantly better in the past period compared to the present