Baseflow Ratio in Catchments with Regolith-Dominated Groundwater Circulation of Different Lithology—Comparison of Kille’s, Rambert’s and Hydrograph Separation Methods

Baseflow separation was performed for 42 small catchments completely built up of either crystalline rocks or folded/unfolded Paleogene flysch rocks. Three different methods were applied—Local minimum (BFI), Kille’s and Rambert’s. Mean total annual runoff in individual catchments varied from 179 to 1132 mm, with an average of 498 mm. Taking into account results for the whole dataset, baseflow participated in 45% ± 15% ratio of the total runoff. Local minimum and Kille’s method results were quite similar: both showed average baseflow participating on 39%/40% of total runoff in unfolded Paleogene catchments, on 29%/29% in folded flysch and 44%/45% in catchments with crystalline basement. Rambert’s method results were 10% to 12% higher from the previous two, reaching 50% in unfolded flysch Paleogene catchments, 41% in folded flysch and 56% in crystalline catchments. Differences might be caused by the nature of Rambert’s method, which is based on recession curves analyses, while the previous two result from discharge statistics. Still, usually only less than 50% of unevaporated precipitation is able to infiltrate and recharge groundwater resources in crystalline rocks and flysch sediments, and folded flysch rocks are sometimes able to absorb only 10–20% of unevaporated precipitation.