Articles | Volume 21, issue 8
Research article
16 Aug 2017
Research article |  | 16 Aug 2017

Simulated hydrologic response to projected changes in precipitation and temperature in the Congo River basin

Noel Aloysius and James Saiers

Abstract. Despite their global significance, the impacts of climate change on water resources and associated ecosystem services in the Congo River basin (CRB) have been understudied. Of particular need for decision makers is the availability of spatial and temporal variability of runoff projections. Here, with the aid of a spatially explicit hydrological model forced with precipitation and temperature projections from 25 global climate models (GCMs) under two greenhouse gas emission scenarios, we explore the variability in modeled runoff in the near future (2016–2035) and mid-century (2046–2065). We find that total runoff from the CRB is projected to increase by 5 % [−9 %; 20 %] (mean – min and max – across model ensembles) over the next two decades and by 7 % [−12 %; 24 %] by mid-century. Projected changes in runoff from subwatersheds distributed within the CRB vary in magnitude and sign. Over the equatorial region and in parts of northern and southwestern CRB, most models project an overall increase in precipitation and, subsequently, runoff. A simulated decrease in precipitation leads to a decline in runoff from headwater regions located in the northeastern and southeastern CRB. Climate model selection plays an important role in future projections for both magnitude and direction of change. The multimodel ensemble approach reveals that precipitation and runoff changes under business-as-usual and avoided greenhouse gas emission scenarios (RCP8.5 vs. RCP4.5) are relatively similar in the near term but deviate in the midterm, which underscores the need for rapid action on climate change adaptation. Our assessment demonstrates the need to include uncertainties in climate model and emission scenario selection during decision-making processes related to climate change mitigation and adaptation.

Short summary
With the aid of a hydrological model and outputs from global climate models (GCMs), we elucidate the spatiotemporal variability of rainfall–runoff in the Congo River basin in the past and in the future under multiple greenhouse gas emission scenarios. We show that the hydrologic model that is forced with outputs from 25 GCMs and two emission scenarios reveal a range of projected changes in precipitation and runoff, and that runoff dynamics are highly sensitive to GCM forcing.