The majority of the world’s fresh water is used for agriculture and a smaller part for domestic and industrial use. In many countries irrigation water for agricultural purposes is unbalanced due to complex distribution systems, limited maintenance, lack of in-situ monitoring systems and unavailable tooling. For that reason it often occurs that large quantities of water are spilled by upstream users which have abundancy, leaving less and too little water for other users, often in downstream plots.
The situation becomes more severe when too little water has to be distributed, resulting in water shortages and disputes. In such situations tools to monitor water use can be extremely helpful to assist water managers in determining locations where water is spilled or simply places where water is used in illegal quantities. Such tools also help determining upcoming water shortage and situations of lack of water at specific agricultural plots. They support identifying unbalanced distribution of water and in situations of shortage to generate more crop per drop.
HydroLogic and eLEAF have joined forces to develop a methodology and toolset to independently determine water use and comparing it with permitted volumes. The satellite-based water auditing application monitors the volumes of water used in irrigated agriculture on a regular basis. It then automatically checks this against the permitted volumes, flagging non-compliance. The methodology is field specific and can be applied for large areas, even in transboundary catchments. The tool developed gives water managers facts to base their practices on and enhances the effectiveness of their operations leading to more equal water distribution across agricultural areas.
Application in South Africa
South Africa is facing a severe water shortage. To regulate the amount of water being used for irrigation, South Africa introduced a water licensing mechanism in the National Water Act (NWA). This mechanism ensures equal distribution and efficient use of the available water resources. Auditing on compliance of water allocation is a major challenge for water managers in South Africa. Irrigated fields are spread over a vast area and the number of fields to audit is enormous.
The Water Auditing service greatly enhances the effectiveness of the agency to audit water use. The service uses evapotranspiration data from satellites, and rainfall data from rain gauges and radar to calculate water use linked to irrigation. The information is compared with the allocated amount of water to evaluate water use per farm. This information is displayed in graph and map format on various spatial scales.