Water quality changes in a small plain agricultural catchment area

Anthropogenic activities in a catchment area influence in a most direct way the surface water quality. Detailed studies of the factors of all production processes in the catchment enable establishing the degree of their possible individual participation in the pollution of that region, which is the first step in finding out the way of its appropriate protection. Such a study we carried out on the example of the Krivaja catchment area (the river Krivaja and the reservoir Zobnatica), in the north of Yugoslavia during the 1980–1992 period. The analysis encompassed natural characteristics of the soil and production activities in the region, which is characterized by numerous point and nonpoint pollution sources. Surface water quality was assessed on the basis of their physical and chemical properties. Besides, inorganic forms of nutrients, first of all nitrogen, were also analyzed. The results indicate deterioration of surface water quality in the catchment during the investigated period. In view of the fact that the state of point pollution sources did not change during the investigation, it is quite clear that nonpoint pollution, having mainly the origin in agricultural production, were the main cause of deterioration of surface water quality.