David Gustafsson

Climate change impact on the water regime of two great Arctic rivers: modeling and uncertainty issues

The ECOlogical Model for Applied Geophysics (ECOMAG) and the HYdrological Predictions for the Environment (HYPE) process-based hydrological models were set up to assess possible impacts of climate change on the hydrological regime of two pan-Arctic great drainage basins of the Lena and the Mackenzie Rivers. We firstly assessed the reliability of the hydrological models to reproduce the historical streamflow series and analyzed the hydrological projections driven by the climate change scenarios. The impacts were assessed for three 30-year periods (early- (2006–2035), mid- (2036–2065), and end-century (2070–2099)) using an ensemble of five global climate models (GCMs) and four Representative Concentration Pathway (RCP) scenarios. Results show, particularly, that the basins react with a multi-year delay to changes in RCP2.6, so-called “mitigation” scenario, and consequently to the potential mitigation measures. Then, we assessed the hydrological projections’ variability, which is caused by the GCM’s and RCP’s uncertainties, and found that the variability rises with the time horizon of the projection, and generally, the projection variability is larger for the Mackenzie than for the Lena. We finally compared the mean annual runoff anomalies projected under the GCM-based data for the twenty-first century with the corresponding anomalies projected under a modified observed climatology using the delta-change method in the Lena basin. We found that the compared projections are closely correlated for the early-century period. Thus, for the Lena basin, the modified observed climatology can be used as driving force for hydrological model-based projections and considered as an alternative to the GCM-based scenarios.

Process refinements improve a hydrological model concept applied to the Niger River basin

This study examines a method to improve a process-oriented hydrological model concept applied to another region than it was first developed for. In principle, we propose to analyse and refine each major hydrological process separately, sequentially, and iteratively. To test the method, the HYPE model concept (HYdrological Predictions for the Environment, originally developed for Sweden) was here applied to the data-sparse Niger River basin in West Africa. Errors in the baseline Niger-HYPE model were analysed to identify inadequately described processes. These process descriptions were subsequently isolated and refined through a set of experiments focusing on concept development, input data enhancement, and multivariable calibration. The refinements were guided by in situ discharge observations, earth observations, local expert knowledge, and previous studies. The results show that the original model concept could simulate the annual cycle of discharge, but not the magnitudes or daily dynamics (56-station average Nash-Sutcliffe Efficiencyxa0=xa0−1). The main processes requiring improved descriptions were precipitation, evaporation, surface runoff, infiltration, soil storage, reservoir regulations, aquifer recharge, and flooding and river-atmosphere exchange in the Inner Niger Delta. Of these, evaporation, flooding and river-atmosphere exchange differ so much between Sweden and the Niger River that the model concept had to be refined. All refinements were synthesized in a new model version (Niger-HYPE2.0) performing significantly better across the basin (56-station average Nash-Sutcliffe Efficiencyxa0=xa00.4). This study demonstrates the danger of applying a model off the shelf, and the obligation to carefully evaluate and revise process descriptions when applying a model concept to a new region. Moreover, the results indicate that our approach to separately, sequentially, and iteratively refine processes together with local experts can substantially improve process-oriented hydrological models.

Impacts of 1.5 and 2.0 °C Warming on Pan‐Arctic River Discharge Into the Hudson Bay Complex Through 2070

Impacts of 1.5 and 2.0 degrees C Warming on Pan-Arctic River Discharge Into the Hudson Bay Complex Through 2070

Arctic Mackenzie Delta channel planform evolution during 1983-2013 utilising Landsat data and hydrological time series

Arctic Mackenzie Delta channel planform evolution during 1983-2013 utilising Landsat data and hydrological time series