Avtor/Urednik		Smolar-Žvanut, Nataša; Vrhovšek, Danijel
Naslov		The impact of drought and reduced flow on aquatic organisms in flowing waters
Tip		članek
Vir		In: Proceedings of the international conference on Drought mitigation and prevention of land desertification; 2002 Apr 21-25, Bled. Bled: International commision on irrigation and drainage,
Leto izdaje		2002
Jezik		eng
Abstrakt		In flowing waters, there are abstractions for domestic supply, hydropower use, fish farming, irrigation, and for technological purposes, all of which have negative effects on aquatic organisms, especially in periods of summer drought. Subsequent reduced flow and related low flow conditions give rise to hydrological, physicochemical, and ecological changes. Such quantity and quality of water should be assured that ecological balance in the river and in the riparian zone, known as ecologically acceptable flow, would not be distorted. Thus rare and endangered species would survive, and quantitative relationships between plant and animal species, and biocoenoses would be preserved. Excessive abstractions for a hydropower plant on the River Tržiška Bistrica, Slovenia, distorted ecological balance at the time of low flow in summer 1993 and 1995. The effect of reduced flow was found in altered species composition of periphyton, changed biomass, species deficit, increased water pollution, absence of fish, and decreased current velocity. High values of periphyton biomass, in which just a few periphyton species were abundant, were also the result of excessive abstractions, particularly in summer and winter. Periphyton samples were taken in the Soča River, Slovenia, in different seasons of 1998 and 1999. A more distinct impact on periphyton was observed at the time of very low flow in summer, Due to low flow combined with high water temperatures, substrata were abundantly overgrown with green algae and pollution increased, which was indicated by higher values of the Pantle-Buck Saprobic Index. The maximum biomass, expressed as ash-free organic matter, was 84 glm2, measured downstream of the dam Podsela. (Abstract truncated at 2000 characters)
Deskriptorji		POWER PLANTS FRESH WATER ECOSYSTEM PLANTS BIOMASS WATER POLLUTANTS ALGAE, GREEN CHLOROPHYLL