For a relevant sub-basin in the national Nile area, counterpart staff has developed a poster illustrating the relative contribution of the various tributaries to the main river. The map uses a hill-shaded Digital Elevation Model (DEM) as background to show the relief of the terrain.

A distinction is made in hydrology between blue and green water. Blue water refers to the water passing through aquifers and watercourses. It represents that part of the water resource most readily available to satisfy societal needs.

Green water is the fraction of the rainfall that evaporates. It constitutes the water supply for all non-irrigated vegetation, including forests, woodlands, grasslands, and rainfed crops. It further includes evaporation from the soil and wet surfaces.

Developing the Blue Water Posters serves multiple purposes. It is used to quality control hydro-meteorological data sets and to identify systematic errors - like missing months or erroneous units. The poster also trains counterpart staff in using GIS for visual explanation. The final product is an effective means for explaining the hydrology of the sub-basin to stakeholders and decision makers.

See full poster