WATER MANAGEMENT BALANCE AS A BASIS FOR WATER USE CONTROL IN RIVER CATCHMENTS - A JEZIORKA RIVER CASE STUDY

Water management balance is a comparison of water resources - surface and ground-water with water users' demands, taking into account interactions between surface water and groundwater, environmental requirements of aquatic and water dependent ecosystems and effects of the operation of hydrotechnical structures. The results of balance analyses provide the basis for formulating restrictions of water use necessary in order to achieve the defined objectives of water protection. The issues most important for determining water management rules are: the degree of implementation of water supply of different users including (quantitative) requirements of the environment, computing the reserves of the available resources, and defining the impact of water uses and hydrotechnical structures on the hydrologic regime. The paper presents methodological basis for preparing water management balances. The basic causes of inaccuracies in balance analysis are discussed. These include the scarcity of hydrologic data on the surface water resources, the need for assessing the amount of the resources in non-monitored river cross-sections, the necessity to reconstruct river flow time series - free from water use impacts, the method of considering the influence of groundwater abstractions on the river flows. Criteria for assessing the degree of water supply task implementation are also presented, with the special attention focused on the criteria for agricultural users.