NASA SATELLITE CAN TRACK MOST WORLD'S IRRIGATION CANALS, STUDY FINDS

A study from the University of Washington has found that a NASA satellite designed to monitor oceans, lakes and rivers can also track water levels in the majority of the world's irrigation canals. Researchers examined roughly 800,000 kilometres of canals across Asia and found the satellite could measure water levels with moderate to high confidence at more than 85% of locations. The satellite involved, the Surface Water and Ocean Topography mission, known as SWOT, is a joint project between NASA and international partners that has been in orbit since December 2022. It was not originally built to monitor waterways as narrow as irrigation canals, many of which measure less than 20 metres wide. The findings were published in the journal Geophysical Research Letters on 30 September.

Irrigation canals carry water from lakes, rivers and reservoirs to farmland across the world, but many regions lack systems to monitor water flow through them, according to the study. Water managers and farmers in these areas currently depend on scattered gauges, physical inspections and local reporting to make decisions about water use, the researchers said. SWOT monitors the Earth's surface water at least once every three weeks using interferometric radar, a technique that compares multiple radar scans over time to detect changes in elevation. While oceans and large lakes are comparatively easy to track using this method, canals sit at the extreme lower limit of what the satellite's instruments can detect, the study noted.

Faisal Hossain, a co-author of the study and professor of civil and environmental engineering at the University of Washington, said the findings may point to a new approach for managing the water systems that support global agriculture. According to the university, the capability could give farmers and water managers a new tool for handling water resources, preparing for droughts and supporting food security. The researchers have not indicated when or whether the monitoring approach might be adopted more widely by agricultural bodies. No further studies or implementation plans were confirmed in the findings.