Influence of Catchment Characteristics and Flood Type on Relationship Between Streamwater Chemistry and Streamflow: Case Study from Carpathian Foothills in Poland

Abstract

The study aimed to determine the influence of catchment characteristics and flood type on the relationship between streamflow and a number of chemical characteristics of streamwater. These were specific electrical conductivity (SC), pH, the concentrations of main ions (Ca2+, Mg2+, Na+, K+, HCO3−, SO42−, and Cl−), and nutrients (NH4+, NO2−, NO3−, and PO43−). These relationships were studied in three small catchments with different geological structure and land use. Several flood types were distinguished based on the factors that initiate flooding and specific conditions during events. Geological factors led to a lower SC and main ion concentrations at a given specific runoff in catchments built of resistant sandstone versus those built of less resistant sediments. A lower concentration of nutrients was detected in the semi-natural woodland catchment versus agricultural and mixed-use catchments, which are strongly impacted by human activity. The strongest correlation between streamflow and the chemical characteristics of water was found in the woodland catchment. Different types of floods were characterized by different ion concentrations. In the woodland catchment, higher SC and higher concentrations of most main ions were noted during storm-induced floods than during floods induced by prolonged rainfall. The opposite was true for the agricultural and mixed-use catchments. During snowmelt floods, SC, NO3−, and most main ion concentrations were higher when the soil was unfrozen in the agricultural and mixed-use catchments versus when the soil was frozen. In the case of the remaining nutrients, lower concentrations of NH4+ were detected during rain-induced floods than during snowmelt floods. The opposite was true of PO43−.