Author/Editor		Smolar-Žvanut, Nataša; Rejec, Alida; Vrhovšek, Danijel
Title		Environmental flow assessment for the Soča river, Slovenia
Type		članek
Source		In: ICOLD 72nd annual meeting; 2004 May 16-22; Seoul. Proceedings of the Symposium on environmental considerations for sustainable dam projects; 2004 May 22; Seoul. Seoul: Korea national committee on large dams,
Publication year		2004
Volume		str. 1-17
Language		eng
Abstract		In the last 10 years there has been strong efforts to improve ecological characteristics of the Slovenian rivers below the dams with determination of environmental flow (EF). EF provision requires defmition of the quantity and quality of water, which is needed to preserve the ecological balance in the river and in the riparian zone. The Soča River is well known for present of endangered fish Marble Trout and rafting opportunities. Downstream the pollution increasing and 71 km from its source is the first dam on the Soča River. Due to very low flows below the Podsela and Plave Dams, the EF was assessed in the years 1996-2002 according to hydro-morphological, biological, and physicochemical parameters. Results of hydrological analyses show substantial changes in the hydrological regime and predominance of gravel deposits with a considerable proportion of coarse grains downstream of the dams. Due to the abstractions, the physicochemical composition of water downstream of the dams was not determined by conditions in the upper reaches of the river but by tributaries downstream of the catchment area. Summer temperatures were 7.2°C higher in comparison with the reference site. Constant flow and rare occurrence of high waters downstream of the dams changes diversity of aquatic organisms compared with reference site upstream of the dams. Downstream of the Podsela Dam, the flow was 0.20 m3s-1 until 2003, the value of the EF determined according ecological method was 1 m3s-1. Flow through the gate of the Ajba Dam was 0.5 m3s-1 until 2003, according to the water management-operating license for the Plave hydropower plant. With the purpose of improving ecological status of the Soca River, EF below the Ajba Dam was determined at a quantity of 2.5 m3s-1.
Descriptors		FRESH WATER WATER POLLUTANTS POWER PLANTS ECOSYSTEM OXYGEN HYDROGEN-ION CONCENTRATION ALGAE, GREEN FISHES