Changes of biogeochemical parameters in the context of long-term trends and different rainfall-runoff conditions were examined with a special focus on various catchment characteristics. The study area is situated in the upper part of the Blanice River catchment, where more than 77% of the area belongs to a Protected Landscape Area and is unique for the most abundant population of the critically endangered freshwater pearl mussel (Margaritifera margaritifera) in Central Europe. The Mann-Kendall test revealed a decrease of nitrogen and phosphorus compounds at the catchment outlet since 2003. The principal component analysis divided nine study catchments into three main groups according to biogeochemical composition (natural, partly anthropogenically influenced, subsurface drainage). Changes of biogeochemical parameters during different runoff conditions revealed a higher release of aluminium, CODMn, dissolved organic carbon and total phosphorus during heavy precipitation event, which could have a negative effect on the vulnerable ecosystem including freshwater pearl mussel.
Our study focuses on assessing trends of hydroclimatic variables and their impact on the runoff regime in the Athabasca River basin in two periods (from the beginning of monitoring until 2011 and 1971−2011). Applied methods included the Mann-Kendall statistical test, linear regression, multiplicative decomposition of data series, the Indicators of Hydrologic Alteration, and the Range of Variability Approach. Temperature records indicated a strong regional warming trend, which influenced decreased snowfall and a declining trend in spring runoff. Our results indicate that between 1971 and 2011 median discharge values decreased by > 20% on the lower and middle courses of the Athabasca River. Although on the upper course the median long-term minimum discharge increased due to the melting of mountain glaciers, on the middle and lower courses a significant decrease occurred. The discharge variability has also increased. All factors and changes are important because they affect the Athabasca-Peace delta’s ecosystem and socioeconomic activities on the lower course.
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