Modeling the Variability of Blue and Green Water Flows in the Congo Basin

The Congo River and its tributaries flow through the second largest rainforest in the world, second only to the Amazon, and are regulated by several natural lakes and wetlands. The river basin that spans on both sides of the equator in Central Africa, possesses significant natural resources, but lacks economic growth due to the continuous political crisis. Published studies describe deforestation as a result of industrial logging and expansion of subsistence agriculture and increasing trends in temperature and precipitation as causes of environmental change in the region. These changes are expected to continue into the future and are likely to alter the spatiotemporal variability of the basin’s blue water (rivers, lakes, wetlands and groundwater storage) and green water (evapotranspiration) flows. Rapid population growth will further exert pressure on available water resources. These changes endanger the health and resilience of ecosystems and their services within the Congo basin. In order to explore the effects of climate and land use on the water resources of the basin and to identify strategies to manage the basin’s water resources for their long-term sustainability, we are conducting an assessment of the basin hydrology. A semi-distributed hydrological modeling framework is being used to simulate the hydrology of the basin. The information on the region’s climate, soil properties and land use and land cover are used in the model. The first phase of the modeling involves simulating the historical hydrology of the basin for the period 1948-2006. The headwater streams drain semi-humid catchments with distinct dry and wet rainy seasons on both sides of the equator. The central part of the basin encompasses dense tropical forest which receives over 2000 mm of rainfall per year. A well-connected lake-wetland system modulates the stream flows in the southern part of the basin. As a result the discharge regime of the main Congo river does not show much variability. Initial model results reveal that the hydrologic behavior of the basin and the seasonality in stream flows due to the different climate, land cover and other physiographic conditions are well-captured. In the second phase, the projected changes in climate, land use, and land cover will be used to predict the changes in blue and green water flows in the future.