EVALUATION OF REVITALIZATION OF AGRICULTU RAL STREAMS

One of the ways of correction of past mistakes are now very popular re vitalizations of water systems. The study is concentrated on revitaliz ation works conducted on small water brooks in agricultural landscape which were in the past technically hard regulated. A great emphasis se t on vegetal background of streams and more complex understanding of a stream in the landscape follows from philosophy of these activities. Unsolved property-legal relationships and complicated administrative p rocedures in trenching outside the bed are hampered in the practice. A main role in the whole process is played by quality bank stands whose importance and ecostabilizing function are distinct. To distinguish d ifferent level of revitalization measures four-stage evaluation was pr oposed. The study summarizes the results of field survey on revitalize d stream of Drazdanka, Decin district. In view of temperature regime t he quality of water was here much influenced by the type of stabilisat ion of the bed. In the course of 790 m stream consolidated by concrete pavers the temperature of water increased on average by 2 degrees C, what affects subsequent oxygen regime. Compared with older data chemic al analyses of water indicated a marked influence of agricultural mana gement in the river basin on quality of water in stream. This seems to be now more satisfactory than in the past, though a presupposed reaso n (reduction of fertilization) was not statistically sufficiently prov ed. Hydrobiological survey also showed a good quality of water environ ment, because the whole stream can be classified in b-mesosaprobic sam ples of macrozoobenthos, namely during 1996. In six sampling points th e following characteristics were investigated: 1. total number of indi viduals per sample; 2. number of species per sample (biodiversity); 3. Shannon-Weaver's index; 4. saprobity index. The best indicator of dis turbance of water environment was the qualitative variable - biodivers ity (2). Quantitative variables are recommended to be replaced by esti mate or calculation of the volume of water environment. Particularly i mportant is the volume of water in the bed near the level of stabilize d discharges. As to macrozoobenthos, the volume of sediments caught in otherwise almost sterile concrete bed is also important. The weeping falling on the water level and below it. This component always formed a maximum regenerated part of cross-section profile in significant com ponent in concrete-consolidated segments.