Managing water across borders

Managing water across borders

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The EU-Africa GMES Earth Observation project combines EO and in situ data to provide real-time quantified information on water need and consumption at the Incomati River Basin

Equitable and efficient water management and allocation, especially across international borders, need accurate information on the use and availability of water resources in space and time. Since the Incomati River Basin is shared between South Africa, Mozambique and Swaziland, transparency is paramount in water allocation to ensure that international obligations are met. An operational monitoring system that covers the entire basin can fulfil this need 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, operates such a system. This joint project by the European Union and Africa Global Monitoring for Environment and Security (GMES) combines earth observation and in situ data to provide real-time quantified information at field scale on (agricultural) water need.

Progress beyond state-of-the-art
The novelty of the WatPLAN project extends beyond the technical use of remote sensing Water Resources | Case Study data. The joint efforts of a consortium of international SMEs and universities have resulted in a unique operational monitoring system that is capable of providing weekly quantified information at field scale.

To obtain this information, the Surface Energy Balance Algorithm for Land (SEBAL) model is used, which is developed and owned by WaterWatch BV from Wageningen, The Netherlands. 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 of the solar energy is reflected of or absorbed by the surface, and part is used for plant growth. Most the components of the energy balance can be quantified from satellite data. The SEBAL model then uses the energy balance to quantify an important component of the water cycle — evapotranspiration (ET). Subsequently, biomass production, the actual and potential water consumption, and water deficit is derived on a pixel-by-pixel basis.

Another important parameter within the WatPLAN project is rainfall. This is derived by combining microwave data from the FEWSNET sensor with in situ rainfall data measured using low-cost meteorology stations installed as part of the project. These data provide valuable insight in various aspects of the water balance important for water management.

For example, combining rainfall and crop water use provides insight into the distribution of renewable water resources across the Incomati Basin. Crop yield can be derived from the biomass production estimates. Dividing crop yield by crop water use gives us water productivity, which defines how much water is used per kg harvestable crop (crop per drop). These data products have the potential to assist different users, including the Tripartite Permanent Technical Committee (TPTC), the Inkomati Catchment Management Agency (ICMA), irrigation boards and farmers in objective and sound water resources management.

The data products provided can also be used as the basic inputs for water accounting, which is a relatively new framework designed to provide explicit spatial information on water depletion and net withdrawal processes in complex river basins. Water accounting contributes to better water allocation, verification of water use and sustainable utilisation of scarce water resources. Other more processoriented products can also be generated such as water productivity or sustainability indicators.

The data products are disseminated using an Internet-based portal where data can be viewed per sub basin, as well as for the various land use classes (forest plantations, natural vegetation, sugarcane and other irrigated crops).

The results
The success of WatPLAN is measured by ways in which the data products are integrated into the stakeholders’ water management systems, and used for water management from field level or catchment scale.

The WatPLAN portal currently has over 70 unique registered stakeholders who frequently visit the data portal. Since September 2011, weekly data has been

provided for the entire basin of 46,469 sq km with information for every 30×30 metre pixel. Data is freely available on www.watplan.com and training material can be viewed online at www.watplan.eu.

WatPLAN contributed to the expansion of the in situ rainfall monitoring system by installing 15 remotely accessible meteorological stations to be used for effective calibration of the earth observation derived rainfall data product.

An encouraging trend is the integration of the WatPLAN information into the water management framework of the Incomati Catchment Management Agency (ICMA), one of the main end-users in South Africa. The ICMA was established to assist the South African Department of Water Affairs in implementing effective Integrated Water Resources Management (IWRM) within the Incomati Water Management Area. The ICMA framework integrates different water resources datasets, including the WatPLAN data and is a frontrunner in integrating earth observation data and models to support operational river management in the region.

The future
Equitable and efficient water allocation to meet international obligations is measured by and achieved through objective and regular monitoring across basins. (Agricultural) water management across the world can greatly benefit from satellite-based operational monitoring systems like WatPLAN, providing accurate quantified information at frequent intervals and across a large area, with field scale details.

The way forward is the progression from Web-based information portals to water management applications available for smartphones and tablets that can be used globally at regional and field scale. The foundation for such applications in Southern Africa has been laid down by WatPLAN and careful first steps toward integrated water management ‘apps’ in ‘appstores’ are taken.

Further integration of data into the stakeholders’ operational water management systems and methods will improve water management at various scales. The project will be completed in 2013, whilst a business continuation plan is currently being formulated.