A Research on Discharge and Temperature Regime of Substantially Altered Karst River

This article presents results of hydrological research on the Ruda River, which is the largest tributary of the Cetina River situated in the Dinaric karst of Croatia. Hydrology of this river has been substantially altered after the construction of the Orlovac Hydropower Plant (HP) and the Buško Blato reservoir in 1973. The main aim of research was generation of new knowledge about the hydrological functioning of the river, where the focus was on the discharge and water temperature regimes that experienced most severe alterations. The methodology is based on classical hydrological, statistical, and time series analysis methods adapted to particularities of study area and available data. Daily and hourly time series of air temperature, precipitation, water temperature, and discharge are analyzed to find trends, change points, inter-annual, seasonal, and sub-daily variations, durations, time shifts, and linear dependencies. The obtained results provide information on effects of climate change, duration of diffuse, conduit, and mixed flow, importance of groundwater exchange, retention times, heat transfer times, referent water temperatures. It determined the role of operational mode of the Orlovac HP in the discharge from spring, inter-annual and sub-annual redistribution of water, hydropeaking, and thermopeaking. The obtained information defines the present state of Ruda River hydrology and illustrates alterations.