Climate effects INCA-P New Papers PERSiST

Climate or land use change – which will have the biggest effect on water quality?

Agricultural intensification for fossil fuel substitution (the land-based bioeconomy) has the potential to affect both food security and water quality. Csilla Farkas and colleagues recently published a study on the possible consequences for surface water quality of future changes in land use due to a greater reliance on the bioeconomy in a time of rapid climate change.

They hypothesized that greater agricultural biomass production would increase the risk for soil loss and enhance suspended sediment yields in streams and that these effects would be exacerbated under a changing climate.

Using hydrological and bias adjusted climate models, the authors compared the effect of seven land use pathways on discharge and sediment transport relative to a baseline scenario under present and future climate conditions for a small headwater stream representative for cereal production areas in southeast Norway. Using PERSiST and INCA-P, they showed that land use change had a greater influence on both future water discharge and sediment losses than possible future climate change. Climate-related changes showed strong seasonal effects. Of the modelled land use (Nordic Bioeconomy) scenarios, a sustainable pathway manifested the least occurrence of extreme flood and sediment loss events under future climate; whereas a pathway based on national self-sufficiency had the highest occurrence of such extreme events.

The study findings highlight the need to place careful attention on land use and soil management in areas likely to be subject to agricultural intensification for bioeconomy purposes and the increasing need to implement environmental mitigation measures to maintain freshwater quality.

Climate effects PERSiST

Modelling streamflow impacts on aquatic ecology

Future patterns of streamflow are likely to be a primary driver of aquatic ecology. Using rainflow runoff models such as PERSiST may be one way to evaluate the possible impacts of climate change and land management on the ecology of vulnerable aquatic species. José Ledesma and colleagues published such a study to evaluate future habitat availability the the Montseny brook newt (Calotriton arnoldi). They concluded that future low streamflow conditions will likely pose a severe threat for the survival of the Montseny brook newt but appropriate local management actions including limiting the expansion of holm oak forest may increase the chances for species survival.

The Montseny brook newt is a critically endangered amphibian species which inhabits a small 20 km2 holm oak and beech forest area in northeast Spain. The species can only live in running waters and might be highly vulnerable to hydrological perturbations such as increased drought frequency that could occur under climate and vegetation cover changes. Scenarios describing potential changes in species habitat due to global and local environmental changes can help identify and prioritize the actions needed for its conservation. Based on knowledge of the species and supported by observations, José Ledesma and colleagues proposed daily low and high streamflow event thresholds for the viability of the species. They used PERSiST to simulate changes in the frequency and duration of streamflow events under two climate and four vegetation cover scenarios for near-future (2031–2050) and far-future (2081–2100) periods in a reference catchment. All future scenarios projected a significant decrease in annual streamflow (between 21% and 67%) with respect to the reference period. The frequency and length of low streamflow events was also projected to dramatically increase. In contrast, the risk of catastrophic drift linked to flash floods was projected to decrease. Local hydrologcial effects associated with a potential change in vegetation toward an expansion of holm oak forests will likely be more important than climate changes in determining threshold low flow conditions. This indicates that consideration of both local (potential changes in vegetation) and global (temperature and precipitation) is essential in simulating future aquatic habitats.

Climate effects INCA-C New Papers PERSiST

Modelling DOC in the Canadian Sub-Arctic

Shanta Sharma recently defended her Masters thesis on modelling dissolved organic carbon (DOC) in the Canadian sub-Arctic. This was one of the most northerly applications of the INCA family of models and brought some unique challenges and insights.

The sub-Arctic in Canada and elsewhere is likely to experience hydroclimatic regime change associated with a rapidly changing climate. Simulations of landscape-scale carbon (C) budgets and pollutant transfer are needed by northern managers and stakeholders to understand and mitigate these possible impacts. The project simulated dissolved organic carbon (DOC) fluxes in a hydrologically complex watershed (Baker Creek) in the Northwest Territories. Discharge, DOC concentration, and DOC export were simulated PERSiST and INCA-C. The models were calibrated against available (2012-2016) discharge and DOC concentration data in sub-catchments of Baker Creek. The model successfully reproduced flow (R2: 0.87–0.94; NS: 0.82–0.91) and captured some aspects of DOC concentration dynamics (R2: 0.19–0.31).

Possible future conditions were simulated using two climate scenarios (elevated temperature (T), elevated temperature and precipitation (T+P)), and compared against a baseline scenario. Average discharge is projected to decrease under scenario T (22–27% of baseline) and increase (116–175% of baseline) under the T+P scenario. In this scenario, early winter increases in discharge suggest a change in hydroclimatic regime from nival to combined nival and pluvial. Future DOC fluxes are projected to decrease (24–27% of baseline) under scenario T and increase (64–81% of baseline) in the T+P scenario, with much of the increase in DOC export occurring during early winter. Any future increase in DOC export from Baker Creek may increase the mobility of previously deposited airborne metal contaminants, e.g., arsenic from Giant Mine.