Ecological assessment of water quality: Comparison of biological-ecological procedures in a rain-fed lowland waterway (Kleine nete, N.Belgium)

Abstract

METHODS AND MATERIALSThe data for the present study were collected in April and September of 1977 and in April of 1978. Altogether 58 samples were taken in 23 brooks belonging to the river basin of the Kleine Nete, and classified as the lowland-type of flowing waterways having an EEC~code of Wl, G4, H2-3 and a temperature T which is low in winter and rather high in summer (PERSOONE, 1977). The discharge of the rivulets changes within a great range, because most of their water is supplied by rain. During dry periods the brooks exhibit low water levels; they might even dry up.The invertebrates, mainly benthic organisms, were collected from plants and the beds of the brooks. A standard hand-net with a mesh width of 0.5 mm and an opening diameter of 30 cm was moved upstream along the bottom and the banks of the brooks, mostly covering a distance of 10 m. Each habitat was sampled in relation to its relative appearance within the sample; e.g. when Elodea covered 40 % of the bottom surface, 40 % of the sample was taken in the Elodea beds. The animals were preserved in 80 % ethyl-alcohol.Before the samples were taken, the temperature, the flow rate of the water and a cross section of the brooks were measured and the different substrates were noted.