From May 1995 to December 1997 and from February 2002 to October 2003, seven quality indicators of water in four mid-field ponds situated in the Odra river valley in the area of the Brzeg Dolny dam, differing in the conditions of water supply, were studied on a monthly basis. The investigations included also surveys of the floral composition of the ground cover around the ponds, water surface measurements with depth sounding, observations of water levels in the ponds, and weekly measurements of groundwater levels in the adjacent area. It was found that the physicochemical composition of water in the ponds depends not only on the existing hydro-meteorological, geological and soil conditions or the land use and management pattern of the valley but also on the local processes of oxidation and reduction.

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