Abstract
The Cetina River is a typical karst watercourse in the deep and wellโdeveloped Dinaric karst. The total length of the Cetina River open streamflow from its spring to the mouth is about 105 km. Estimated mean annual rainfall is 1380 mm. The Cetina catchment is built of Triassic, Jurassic, and Cretaceous carbonate strata. The western part of the catchment by the Cetina River is referred to as the โdirectโ or topographic catchment. It was defined based on surface morphologic forms, by connection between mountain chain peaks. This part of the catchment is almost entirely situated in the Republic of Croatia. The eastern part of the catchment is referred to as the โindirectโ catchment, and is mainly situated in BosniaโHerzegovina. Water from the โindirectโ catchment emerges from the western โdirectโ catchment in numerous permanent and temporary karst springs. Since 1960, numerous hydrotechnical works have been carried out on the Cetina River and within its catchment. Five hydroelectric power plants (HEPPs), five reservoirs, and three long tunnels and pipelines have been built. Their operation has significantly altered the natural hydrological regime. The Cetina River is divided into two hydrological reaches. In the 65 km upstream, the hydrological regime was redistributed within the year: low flows had increased and high flows had decreased, although the mean annual discharge remained the same. Part of the Cetina watercourse downstream from the Pranฤeviฤi Reservoir lost the majority of its flow. The mean annual discharges dropped from 100 m^3^ s^โ1^ to less than 10 m^3^ s^โ1^ because of the Zakuฤac HEPP development. Copyright ยฉ 2003 John Wiley & Sons, Ltd.