INFLUENCE OF MSCIWOJOW PRE-DAM RESERVOIR ON WATER QUALITY IN THE WATER RESERVOIR DAM AND BELOW THE RESERVOIR

The paper presents results of research carried out in the period of November 2006 - October 2008 and focused on the influence of the Msciwojow pre-dam reservoir on the quality of water in the main reservoir and below. The following water quality indicators were determined: NO3-, NO2-, NH4+, PO43, water temperature, pH, electrolytic conductivity, dissolved oxygen and chlorophyll a. The measurements were carried out for the Msciwojow reservoir, located on the Wierzbiak river in Lower Silesia province (south-western part of Poland). Contribution of the pre-dam reservoir to the reduction of pollutants in water of the Wierzbiak and Zimnik rivers flowing into the main reservoir was analyzed. During the performed analyzes the following reductions of the main physico-chemical indicators in the pre-dam reservoir were observed, ie nitrates(V) by 69.9 %, phosphates by 32.9 %, nitrates(III) by 63.2 % and ammonia by 62.9 %. The increase of water temperature, pH and dissolved oxygen was also recorded. In the study the quality of water flowing into the Msciwojow reservoir, outflowing water and water stored in the pre-dam and in the main reservoir was assessed. The obtained results showed that the pre-dam reservoir contributed to the improvement of the quality of water flowing into the main reservoir. Proposals for defining dimensions of pre-dam reservoirs and designing principles were presented.