Author(s): Beatriz Negreiros; Silke Wieprecht; Sebastian Schwindt
Linked Author(s): Silke Wieprecht, Sebastian Schwindt
Keywords: River analyst dissolved oxygen hydraulic conductivity hyporheic connectivity morphological units
Abstract: The hyporheic zone of rivers hosts critical exchange processes between surface and subsurface water, governed by the sedimentary characteristics of the riverbed and hydraulic conditions. In-situ measurements of riverbed characteristics are key to quantifying these ecologically relevant exchange processes, including grain size distribution, interstitial dissolved oxygen, and riverbed permeability. However, such analysis is challenging because these quantities change in space and time, with different units, and little data amounts. In addition, statistical attributes, such as non-normality, may prohibit common analysis techniques such as ANOVA or Pearson correlation. This is why we ran extended statistical analyses on a large database with years-long observations. Statistical significance between geochemical parameters served for testing two hypotheses. Notably, we hypothesize that (1) riverbed permeability governs the transport of oxygen-rich surface water into the hyporheic zone; and (2) oxygen content in the hyporheic zone varies with morphological units. The results based on 1768 measurements from 18 rivers show that interstitial dissolved oxygen (IDO) is not normally distributed. To enable comparisons of non-normally distributed variables, we use Spearman rank correlation and Kruskal Wallis tests. These tests suggest that the first hypothesis can be accepted with a statistically significant confidence level (p < 0.05) and a Spearman correlation of rs = 0.54 between IDO and a non-dimensional permeability proxy. To test the second hypothesis, we compute a non-dimensional halving depth, which expresses the sediment depth where IDO values halves in relation to the nearest-surface value. The tests show that the distributions of the halving depths do not significantly differ between morphological units of glides, riffles, and pools. In conclusion, this study identifies a significant influence of sediment permeability on IDO in the hyporheic zone, emphasizing the need for permeability-focused approaches in river restoration.
Year: 2025