River Basins - Dataviz

select the detail level of the basin

Detail levels of the basin:

Use the slider to select the detail level of the basin. The higher the number, the greater level of detail. The upper limit number (3-6, depending on the river) is variable across basins and depends on the level of detail of the sub-basin delineation. The boundary of the basins is drawn based on elevation data and usually corresponds to a main ridge.

Basins at a given level aggregate the flow from basins at higher levels, until ultimately all basins feed into the single major basin at Level 1. Each basin contains a tributary of the major river after which the main basin is named.

River Basin Rainfall

Compare with previous years:

How to read this chart:

River basin rainfall is shown for rainy season of that region, with each month separated into 10-day periods (1 | 2 | 3). Users can compare the current year to one of the years on record by choosing a year from the dropdown list; the chosen year will appear highlighted on the graph.

The current year is shown as a red line with a point for each decade of the month. Past years appear as grey lines, allowing the user to see how the current year compares to flood and drought years.

The average appears as a black line.

The area between “STD +1” and “STD -1”, plus or minus one standard deviation, contains 68% percent of historical data for the basin and is shown by yellow lines.

The area between “STD +2” and “STD -2”, plus or minus two standard deviations, contains 95% of all historical data and is shown by orange lines. Rainfall beyond two standard deviations should be considered exceptional; historical trend lines above or below the orange lines mark years of heavy flooding or extreme drought.

Overview

The river basins visualization provides rainfall data for the last 35+ years for five of the world’s major rivers (Limpopo, Nile, Orange, Shabelli-Juba, and Zambesi), allowing users to track whether the current basin-wide rainfall is within the normal range, or whether there is a risk of drought and lower river flows or flooding and high river flows.

NB: River basin rainfall that is very high compared to the historical record is not necessarily an indicator of flooding within the basin or downstream from it. Other factors must be taken into consideration to determine whether flooding will occur. However, high rainfall levels can be useful to raise the alarm level or flag a potentially serious situation.

Data sources

Data is provided by CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data), produced by the Climate Hazards Group at the University of California, Santa Barbara.

CHIRPS is a 35+ year quasi-global rainfall dataset. Spanning 50°S-50°N (and all longitudes), starting in 1981 to near-present, CHIRPS incorporates 0.05° resolution satellite imagery with in-situ station data to create gridded rainfall time series for trend analysis and seasonal drought monitoring. CHIRPS data is available at 5 and 10 day accumulations. CHIRPS is free to use and easily accessible at: http://chg.geog.ucsb.edu/data/chirps/

VAM processes this data in-house by aggregating it over the river basins (and sub-basins) on a 10-day basis and deriving cumulative rainfall curves of basin rainfall. The historical data is also pre-processed and used to define bounds of historical variation against which to compare the current season.