Modeling Impact of Changing Hydroclimatic Regime on Dissolved Organic Carbon Export from Baker Creek Catchment

Abstract

The subarctic is anticipated to undergo hydroclimatic regime change, which can impact hydrological processes and water yield. Explaining landscape-scale carbon (C) budgets and pollutant transfer is necessary for understanding the impact of changing hydroclimatic regimes. This research investigates dissolved organic carbon (DOC) fluxes in a hydrologically complex watershed (Baker Creek) in the Northwest Territories. Discharge, DOC concentration, and DOC export were simulated using a rainfall-runoff model (PERSiST), and a catchment biogeochemical model (INCA-C). Model calibration (2012–2016) was done using available discharge and DOC concentration data in sub-catchments of Baker Creek. The model successfully reproduced hydrological flow in the catchment (R2: 0.87–0.94; NS: 0.82–0.91) and reasonably captured DOC concentration (R2: 0.19–0.31). Future conditions were simulated using two climate scenarios (elevated temperature, elevated temperature and precipitation), and compared against a scenario with baseline conditions. Average discharge over 30 years is predicted to decrease under elevated temperature scenario (22–27% of baseline) and increase (116–175% of baseline) under elevated temperature and precipitation scenario. For this scenario, discharge increases in early winter indicate a change in hydroclimatic regime from nival to combined nival and pluvial. Average DOC flux over 30 years is predicted to decrease (24–27% of baseline) under elevated temperature scenario and increase (64–81% of baseline) under elevated temperature and precipitation scenario where a large increase in DOC export will occur in early winter. DOC flux in Baker Creek is controlled by runoff in the catchment. Under future climate scenario, increased DOC export from Baker Creek catchment with increased discharge can increase the mobility of previously deposited airborne metal contaminants such as arsenic from Giant Mine.