ALBERT

Description: Climate and land-use changes are going to leave an indelible mark on the hydrology and globally significant peatlands of the Hudson Bay Lowlands (HBL), Canada. With forecasts for warmer and drier conditions over the next century, the relative contribution of water from surface and subsurface sources affecting both water quantity and quality will undoubtedly shift. Unfortunately, no empirical data exist for any streams or rivers of the HBL on the relative contributions of surface water and groundwater to streamflow, making assessment of future change difficult. Here we report the first data on sources of water to streams and rivers across a range of catchment sizes in the James Bay Lowland (JBL) ecoregion of the HBL. Solute chemistry was determined for a range of potential end members, end members were identified, and a chemical mixing model approach was used to determine the relative end-member contributions to streamflow across a range of catchment sizes (~30-2000 km 2 ). The relative contributions of bedrock-derived groundwater to streamflow increased with catchment area from 40% under dry conditions, and were ~50% lower under wet conditions across all catchments. Runoff contributions from peatlands were relatively constant over space and time (53-67%), but the fraction of streamflow composed of rain and snowmelt varied dramatically between wet and dry periods, and among catchments. Given the importance of peatland-derived surface waters, future changes in precipitation and temperature could have significant implications for streamflow in the JBL, particularly during summer base-flow conditions. Moreover, the definition of reference catchments for baseline/impact monitoring must be carefully considered, given the potential for variation in hydrochemistry across physiographically similar catchments. Content Type Journal Article Pages 236-250 DOI 10.1657/1938-4246-46.1.236 Authors Julia Orlova, Department of Geography, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 3K7, Canada Brian A. Branfireun, Department of Geography, University of Toronto Mississauga, 3359 Mississauga Road North, Mississauga, Ontario, L5L 1C6, Canada Journal Arctic, Antarctic, and Alpine Research Online ISSN 1938-4246 Print ISSN 1523-0430 Journal Volume Volume 46 Journal Issue Volume 46, Number 1 / February 2014