More about this website

Water is a critical and scarce resource in southern Africa and is likely to become even more so as the regional impacts of global climate change become more evident. Being able to accurately and repeatedly monitor available water resources across the entire landscape is a key information requirement for successful water resource management.

GeoTerraImage has developed a unique, web-accessible water resource monitoring service, that provides on a monthly basis, detailed, wall-to-wall countrywide inventory of all surface water features across South Africa.

This service can also be easily expanded to cover international cross-border hydrological catchments across SADC.

The web-site provides the means for water resource managers, and other interested parties to be able to access highly detailed, reliable, and regular information on the status of water resources across the country, in support of activities such as compliance monitoring, water security, water licence applications and water resource inventory.

The advantage of this system is that it provides extremely cost-efficient, desk-top based access to reliable monthly data for all surface water bodies across South Africa, without reliance on expensive in-situ based monitoring equipment; with the associated risks and costs of instrumentation installation, maintenance, and possible loss.

Cloud-based satellite image data archives, combined with big data processing capabilities are used to automatically generate spatially detailed information on the extent of all surface water features, from small farm dams and natural pans to large impoundments, across the South African landscape, on a monthly basis.

The service is based primarily on the European Space Agency's (ESA) 20m resolution Sentinel2 satellite imagery, which allows all surface water bodies typically > 0.25 ha to be identified and mapped on a repeatable and accurate manner.

The Sentinel2 system currently consists of two satellites (2A and 2B) working in tandem, and is able to provide regular 5-day image updates over any area globally, which means that ± 5 observations per month are feasible over any location. The multiple individual observations per month are composited into a single, optimal, minimal cloud obscured dataset from which the monthly total surface water areas are determined.

Should any area be obscured by cloud cover in all satellite over-passes within any one month period, then this is flagged and illustrated in the map presentations as a grey, cloud-obscured area, and recorded in the tabulated data as a cloud index. Water area statistics for catchments with very high cloud cover percentages in any given month should thus be used with caution, since this means that the total water area for that month may be under-represented.

The public web-accessible information describes both visually and as tabulate summaries, the current months total surface water, area as well as the previous two months total water areas, the long-term maximum water extent and an index of long-term water occurrence levels.

All water statistics and spatial maps are updated in the 1st week of each month, according to the latest surface water areas detected in the preceding month, i.e. on 1st June the water for May is calculated and uploaded to the web-site.

The long-term data sets are derived from the total archive of Sentinel2 imagery, covering the period from late 2015 to present, and are again updated and revised and updated each month.

By clicking on one or more quaternary catchments, the website will display the statistics of the current, previous and long-term comparative monthly total water surface areas in the selected catchment(s).

Subscribers to the commercial paid-for-service can access the actual digital monthly water maps (which are provided in GIS compatible raster format, based on 20m cells), and comprehensive tabulated water data that contain monthly and long-term surface water area statistics per quaternary catchment, from October 2015 to present; all of which are updated monthly.

Additional technical background information on the surface water modelling and supporting technologies can be found at the following link:


The surface water area monitoring service will be expanded in the near future to incorporate water volume estimates on a per dam and quaternary catchment basis, with predictive flow and volume estimates being implemented longer term.

In addition, the following enhancements are also planned:
  • Annual or Monthly Coastal and Estuarine high water delineations.
  • Modelled wetland boundaries
  • Water classification (natural and man-made features)
  • Extending water coverage and monitoring across southern Africa (transfrontier catchments)

Paid-for-Commercial Water Data Access Subscriptions:

  • Subscribers to the monthly water service are provided with full access to the monthly surface water area datasets, both as GIS compatible, raster data layers, and/or tabulated spreadsheets.
  • Subscribers receive full access to the full monthly history of all water data from 2015 to present.
  • Subscribers are able to access the datasets through conventional data download facilities, or by linking their own data / reporting systems directly to the cloud-based data bucket repositories, depending in requirements and capabilities.
  • Subscribers can determine their own areas-of-interest for monthly water data coverage.
  • Please contact GeoTerraImage (by the 'feedback' icon on the web-site) should you be interested in a paid-for-data subscription and wish to know more.
  • Sample datasets of monthly water coverages from 2015 to present are available for evaluation upon request.


  • Hydro Catchment
  • Water Surface Area
  • Cloud Obscured
  • Bright Bare Surface