Climate Change Impact on River Discharges in Bosnia and Herzegovina: A Case Study of the Lower Vrbas River Basin

Abstract

The paper analyses the impact of recent climate change on river discharges in Bosnia and Herzegovina. Data on mean monthly precipitation, temperature and discharges from the Banjaluka meteorological station and from the Delibašino Selo (Banjaluka) hydrological station during the 1961–2016 periods were used for calculations of annual and seasonal trends in the Lower Vrbas River basin (which was chosen for the case study). The nonparametric Mann-Kendall test and the Sen’s method were used to assess the trend magnitude and its statistical significance, whereas the Pearson correlation index was chosen to detect the connections between climatic and river discharge data series. Given the results, a significant warming tendency was present throughout the year. Annual temperature increased 0.46 ℃ per decade. Unlike temperature, trends in annual and seasonal precipitation were mixed in sign, but were all insignificant. During the observed period, river discharges displayed a significant negative correlation with temperatures throughout the year (insignificant only in winter), whereas links with precipitation were significant and positive. As a result of the determined climate variability, annual river discharges showed a significant downward trend in the range of −8.74 m3/s per decade. Negative discharge trends were detected in all seasons, but were most prominent in winter and spring. The observed changes in river discharges were strongly related to the large-scale atmospheric circulation patterns over the Northern Hemisphere: the Artic Oscillation pattern, the East-Atlantic pattern, the North Atlantic Oscillation and the East Atlantic-West Russia pattern. A significant warming of the climate system, combined with the downward discharge trends throughout the year and precipitation decrease in summer, will lead to decreased water availability over the Lower Vrbas River basin in the future. Given the stated, adaptation towards the observed and projected climate change will be necessary in all key sectors in Bosnia and Herzegovina such as agriculture, energetics (hydropower) and tourism. The adaptation and mitigation options aimed to increase their resilience were considered.