GEOLINKS International Conference 2020, Book 1
HYDROLOGICAL MODELLING AND ESTIMATION OF THE SEDIMENTS ACCUMULATION IN BOVILLA RESERVOIR
PhD Student Klodian Zaimi, Assoc. Prof. Fatos Hoxhaj
Bovilla reservoir is the main source of water supply for around 1 million inhabitants in Tirana, the capital of Albania. The reservoir was created in 1998 from Bovilla Dam and belongs to the upper part of the Terkuza River catchment. The dam previously was planned in a smaller size for irrigation purposes. Intense erosion due to large deforestations followed by increasing nutrient run-off from cultivated land is a challenge for the Bovilla Dam management authority because it is influencing the water quality in daily use and decreasing the dam lifespan in long term. Zall Bastari stream transports high amounts of solid materials. Other streams show also a strong torrential character, after rainfall events the water level suddenly rises which leads to massive erosion. Daily meteorological parameters and 30 meters Digital Terrain Model is used together with Land Cover Map in the HEC-HSM hydrological model which is designed to simulate the complete hydrologic processes of watershed systems, including the erosion and sediment transport. The lack of water level and discharge data made impossible the calibration of the hydrological model. The creation of a new data series for the daily discharges was crucial for further analyzes of the sediment transport and accumulation into the reservoir. Bovilla basin has been divided into many sub-basins in order to better calculate the inflow at the reservoir. The lack of previous bathymetric data caused the usage of alternative ways to calculate total accumulated sediment into the reservoir instead of the classical way in lifespan analysis. The characteristics of the sediment in the sub-basins and in the riverbed have been defined through gradation curves got from some available data. Sediment yield has been evaluated based on the conditions of the previous 21 years, from the construction of the dam in 1996 to nowadays. The old storage curve has been interpolated to be compared with the one defined after the survey specifically done in 2017. The analysis was very important to understand the way haw are accumulated sediment into the reservoir but also their distribution through the reservoir bed.
hydrological model, sediments, land-use, catchment, reservoir