Articles | Volume 18, issue 12
Hydrol. Earth Syst. Sci., 18, 5125–5148, 2014
Hydrol. Earth Syst. Sci., 18, 5125–5148, 2014

Research article 12 Dec 2014

Research article | 12 Dec 2014

Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

J. Crossman1,2, M. N. Futter3, P. G. Whitehead2, E. Stainsby4, H. M. Baulch5, L. Jin6, S. K. Oni7, R. L. Wilby8, and P. J. Dillon1 J. Crossman et al.
  • 1Chemical Sciences, Trent University, Peterborough, ON, Canada
  • 2Oxford University Centre for the Environment, Oxford University, Oxford, UK
  • 3Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
  • 4Ontario Ministry of Environment, Etobicoke, ON, Canada
  • 5School of Environment and Sustainability and Global Institute for Water Security, University of Saskatchewan, Saskatoon, SK, Canada
  • 6Department of Geology, State University of New York College at Cortland, Cortland, NY, USA
  • 7Department of Forest Ecology and Management, Swedish University of Agricultural Science, Umeå, Sweden
  • 8Department of Geography, Loughborough University, Leicestershire, UK

Abstract. Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which are expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as it is to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of global climate model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the INtegrated CAtchment model of Phosphorus dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968–1997) to two future periods: 2020–2049 and 2060–2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivities) were highly varied. Sensitivity was governed by quaternary geology (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

Short summary
We projected potential hydrochemical responses in four neighbouring catchments to a range of future climates. The highly variable responses in streamflow and total phosphorus (TP) were governed by geology and flow pathways, where larger catchment responses were proportional to greater soil clay content. This suggests clay content might be used as an indicator of catchment sensitivity to climate change, and highlights the need for catchment-specific management plans.