A new concept for the determination of reference low flows of natural watercourses - the guaranteed minimum - has recently been introduced into the water management practice. Appreciating the significance underlying the definition of low flows in all segments of water management (municipal and industrial water supply, wastewater discharge, irrigation, navigation, hydropower, water protection, etc.), the author believes that all aspects of the problem must duly be considered, examined and identified. The doubts and issues raised by the guaranteed minimum concept in the domain of random-probabilistic phenomena, such as river discharge, are discussed in the paper.

The paper contains description of potential approaches to better defining of distribution curves parameters for low water levels on water courses that sporadically dry up, also including additional information on the length of dry period. Computed results are given for the example of minimum annual discharge on several rivers in the Velika Morava basin, Serbia (Serbia and Montenegro).

Man-made lakes cause direct and indirect changes in environmental conditions downstream of the water reservoir. Management must consider these water quality and environmental effects as well as uses of the river below the water reservoir.

Wastewater from the Novi Sad Oil Refinery, Serbia (Serbia and Montenegro) had been previously discharged to the Danube river between the raw water wells. In order to protect water supply source, the collector discharge was displaced downstream, outside the raw water wells area. In 2004, the quality of Danube river water and sediment was monitored at the sites of the old and new collector discharge of the Oil Refinery wastewaters, as well as at two control (reference) sites. The paper presents chemical quality parameters of water and sediment, characterizing oil contamination. Significantly increased contents of oil contaminant were measured in the Danube river sediment at the old discharge site compared to other sampling points, which is a consequence of many-year accumulation, as well as in the Danube river water at the new discharge site, as a consequence of the present wastewater discharge.

During 2004 the referent monitoring of chemical quality of surface water and sediments in some protected areas in Vojvodina was conducted as a supplement to the regular monitoring program in Vojvodina. The aim of the study was to establish the chemical quality of surface water and sediments. It is concluded that the water quality satisfies the criteria of class 1/2 according to national legislation. With regard to contamination of sediments with organic micropollutants the sediment of Lake Ludos may be considered as potentially problematic because the Canadian empiric effect guideline value as well as sediment quality reference values according to Dutch legislation were exceeded for DDT and its derivatives.