Abstract
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.
Highlights
Sustainable management of water resources for food production, supply of safe drinking water and provision of adequate sanitation present immense challenges in many countries of central Africa where the Congo River basin (CRB) is located (IPCC, 2014; UNEP, 2011; World Food Program, 2014)
Historical observations of average annual precipitation vary from 1100 mm in the southeastern portion of the CRB to 1600 mm in the CRB’s equatorial region
We present the uncertainty associated with global climate models (GCMs) and scenario selection by quantifying seasonal and intermodel variability in Accessible flows (AFs) at eight major tributaries that drain watersheds across a range of climatic regions on both sides of the Equator (Fig. 9)
Summary
Sustainable management of water resources for food production, supply of safe drinking water and provision of adequate sanitation present immense challenges in many countries of central Africa where the Congo River basin (CRB) is located (IPCC, 2014; UNEP, 2011; World Food Program, 2014). The economies of the nine countries that share the waters of the CRB are agriculture based (World Bank Group, 2014) and are vulnerable to the impacts of climate change. Despite the abundant water and land resources and favorable climates, the basin countries are net importers of staple food grains and are far behind in achieving Millennium Development Goals (Bruinsma, 2003; Molden, 2007; UNEP, 2011). Historical, present and near-future greenhouse gas emissions in the CRB countries constitute a small fraction of global emissions; the impacts of climate change on water resources are expected to be severe due to the region’s heavy reliance on natural resources (e.g., agriculture and forestry) (Collier et al, 2008; DeFries and Rosenzweig, 2010; Niang et al, 2014). The limited adaptation capacity in the CRB region is expected to cause water and food security
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