How does baseflow contribution affect catchment C-Q relationships? A continental synthesis using a Bayesian Hierarchical Model
- 1Department of Infrastructure Engineering, University of Melbourne, Victoria, 3010, Australia (danlu.guo@unimelb.edu.au)
- 2EPFL, Physics of Aquatic Systems Laboratory, Margaretha Kamprad Chair, Lausanne, Switzerland
- 3Department of Civil Engineering, Monash University, Victoria, 3800, Australia
- 4Bureau of Meteorology, Science and Innovations Group, Parkes ACT 2600, Australia
- 5School of Geographical Sciences, Nanjing University of Information Science & Technology, Nanjing 210044, China
- 6Water Research Centre, School of Civil and Environmental Engineering, UNSW Sydney, NSW 2052, Australia
- 7Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, Australia
- 8National Centre for Groundwater Research and Training (NCGRT), Adelaide, SA, Australia
Understanding concentration-discharge (C-Q) relationships is critical to inform catchment export processes for solute and particulates. The contribution of baseflow to streamflow has been found to affect C-Q relationships in some catchments in previous studies. Current understanding on the effects of baseflow contribution in shaping the C-Q patterns is largely limited to temperate catchments, but we still lack quantitative understanding of these effects across a wide range of climates (e.g., arid, tropical and subtropical). The study aims to assess how baseflow contributions within individual catchments influence C-Q slopes across Australia. The wide range of hydro-climatic regimes and land use/land cover conditions in Australian catchments make this continent the ideal experimental field to gain such an understanding. We analyzed 157 catchments in Australia spanning five climate zones, for six water quality variables: electrical conductivity (EC), total phosphorus (TP), soluble reactive phosphorus (SRP), total suspended solids (TSS), the sum of nitrate and nitrite (NOx) and total nitrogen (TN). The impact of baseflow contributions was defined by the median and the range of daily baseflow indices (BFI_m and BFI_range, respectively) for each catchment. A novel Bayesian hierarchical model was developed to synthesize these effects for individual catchments across the continent.
Sediments and nutrient species (TSS, NOx, TN and TP) generally show positive C-Q slopes for most catchments, suggesting a dominance of mobilization export patterns. Further, TSS, NOx and TP show stronger mobilization (i.e., steeper positive C-Q slopes) in catchments with higher values in both the BFI_m and BFI_range, while these two metrics are also positively correlated for most catchments. The enhanced mobilization in catchments with higher BFI_m or BFI_range might be explained by more variable flow pathways in catchments with higher baseflow contributions. In such catchments, the more variable flow pathways can lead to higher concentration gradients between low flows and high flows. These gradients are due to different dominant flow pathways and contributions of groundwater/slow subsurface flow and surface water sources. Our results highlight the need for further studies focusing on identifying and quantifying: a) the influences of temporal variations of baseflow contributions on flow pathways, and b) the impacts of variable flow pathways on catchment C-Q relationships.
How to cite: Guo, D., Minaudo, C., Lintern, A., Bende-Michl, U., Liu, S., Zhang, K., and Duvert, C.: How does baseflow contribution affect catchment C-Q relationships? A continental synthesis using a Bayesian Hierarchical Model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6847, https://doi.org/10.5194/egusphere-egu22-6847, 2022.
