Water quality in forests small retention reservoirs in southern Poland – case study

Abstract

This paper provides an analysis of water quality in three newly constructed small water retention reservoirs (Rudziczka, Niemysłowice I and Paciorkowy) located in forested areas of the forest district Prudnik in the Opolskie Province (southern Poland). The main purpose of these reservoirs is not only water retention, but also flood safety, fire protection, recreation and ecology. This paper presents the results of research carried out in December 2014 and May 2015. The assessment of water quality was performed in accordance with the applicable provisions on water quality assessment. Moreover, an assessment of eutrophication of water and of the usability of water in reservoirs is given (an analysis of suitability of water as a fish habitat). The research shows that the investigated waters are of quality class I in terms of the values of electrolytic conductivity, nitrates, nitrites, dissolved oxygen COD Mn , calcium, magnesium and general hardness. In terms of the temperature (the Rudziczka reservoir), and the content of ammonia and phosphates they were of quality class II. The reaction, BOD 5 and sulphates and chlorides content exceeded the threshold values for class II. It was also found that the investigated waters are not eutrophic. Based on the indicators such as reaction, dissolved oxygen, ammonia nitrogen and temperature, the waters in all the reservoirs except for Rudziczka met the quality requirements for habitats of salmonids and cyprinids. The living conditions for fish are deteriorated most by the increased levels of BOD 5 and of nitrites in the Rudziczka and Paciorkowy reservoirs. The analysis of seasonal fluctuation in concentrations of water quality indicators in the investigated water bodies showed that in winter the concentrations of indicators were higher for nitrates, phosphates, electrolytic conductivity, calcium and general hardness and lower for temperature, reaction, nitrites, ammonia and dissolved oxygen. While the water in the Paciorkowy reservoir had the worst quality, the surface water in the Rudziczka reservoir had the best quality. The research initiated in small forests water retention reservoirs provides preliminary information on water quality and the importance of investigated reservoirs for increased retention.