Hydromorphological assessments at the Irpin river – methodological hints and first findings

Practical hints are given to ease the planning and implementation o f habitat assessments in terms o f hydromorphological elements as described in the WFD. A reach o f the r. Irpin, located between 2 impoundments, was classified as partly moderate and partly good. The river reach between Didivshchyna and Tomashivka (Kyiv Oblast) did not include the existence of the nearby weirs and impoundments upstream and downstream of the section. When considering a bigger part of the Irpin, it is obvious that the river, according to the WFD, must be considered already as heavily modified water body (“HMWB”), mainly because of the interruption of the longitudinal continuity. Frequency of weirs and impoundment sizes by far exceed the tolerable level: the distance between impoundments should be at least 10 km, their length not more than 300 m, but some of them reach several kilometers. As a consequence the natural sediment transport capacity is strongly reduced, leading to sedimentation of inorganic and organic materials, oxygen depletion in deeper water layers, methane formation and impacts on biodiversity. Migration of fish and aquatic insects up and downstream are restricted. Additional problems and risks of reaching a good ecological potential or status are due to the high share of agricultural land use in several subbasins while buffer zones are rather small or sometimes missing.