Equitable and efficient water management and allocation, especially across country borders, needs accurate information on the use and availability of water resources in space and time. An operational monitoring system that covered the Incomati River Basin helped in fulfilling the need for transparency by providing quantified information on water use.

The “Spatial Earth Observation Monitoring for Planning and Water Allocation in the International Incomati Basin project” - or WatPLAN – set up such an operational monitoring system. This joint European Union-Africa GMES earth observation project combines earth observation and in situ data to provide near-real time quantified information at field scale on (agricultural) water need and consumption.

The joint efforts of a consortium of international Small and Medium Enterprises (SMEs) and universities have resulted in a unique operational monitoring system that is capable of providing weekly quantified information at field scale by using the Surface Energy Balance Algorithm for Land (SEBAL) model. This model has been applied and evaluated in more than 30 countries including many African countries. The energy balance describes how solar energy is distributed; part is reflected or absorbed by the surface, and part is used for plant growth. These components of the energy balance can be derived from satellite data using the model to quantify an important component of the water cycle - Evapotranspiration (ET). Subsequently, biomass production, actual-, and potential water consumption, and water deficit are derived on a pixel-by-pixel basis.

Rainfall is another important parameter within the project and is derived by combining microwave data from the FEWS-NET sensor with in situ rainfall data measured using low cost meteorology stations installed as part of the project. These data products provide valuable insight in various aspects of the water balance important for water management. Such aspects include the distribution of renewable water resources, crop yield and water productivity.

For instance, these data products can be used by technical committees and agencies, irrigation boards and farmers and also for water accounting. Water accounting contributes to better water allocation, verification of water use and sustainable utilisation of scarce water resources.