NASA Earth Observatory on October 2, 2026 published satellite imagery showing the Gandak River, also called the Narayani, spreading far beyond its normal channel after days of torrential rain in Nepal. The agency said the river reached record levels in parts of Nepal and India.
What the satellites recorded
According to NASA, the images were captured by the MODIS (Moderate Resolution Imaging Spectroradiometer) instruments on the Terra and Aqua satellites on September 20, 2026, before the flooding, and on September 29, 2026, during it.
The agency said the false-color images combine observations of infrared and visible light, using MODIS bands 7-2-1, to make it easier to distinguish water. In the resulting views, NASA said floodwater appears blue, vegetation is bright green and clouds are light blue.
The imagery was produced by Lauren Dauphin using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview, with the accompanying story written by Adam Voiland.
The flooding
NASA said storms drenched Nepal's mountainous Lumbini and Gandaki provinces with waves of torrential rain between September 24 and 27. The deluge, which it described as arriving late in the monsoon season, triggered landslides and pushed the river to record levels in both Nepal and India.
With runoff streaming into the braided river system, water overtopped and breached embankments in several areas, inundating farmland and settlements along the river for hundreds of kilometers, according to the agency. It said news reports indicated that flooding and landslides had affected hundreds of villages and displaced thousands of people as authorities assessed the damage.
NASA noted that in many areas water inundated seasonal fields on low-lying deposits of sand and silt within the river's channel, called diara, where flooding is expected. But it said embankments were also breached, flooding several settled areas including parts of Bagaha, Areraj and Fulia Khand.
Record gauge readings
Data from Nepal's Department of Hydrology and Meteorology indicated that a gauge in Devghāṭ reached as high as 11.94 meters on September 27, the highest since measurements began there in the 1960s, NASA said.
Citing news reports, the agency said gauges in India along the Gandak that set new high-water marks included Bagaha, Dumariaghat, Rewaghat and Lalganj.
Tools NASA points to
NASA said it has several tools and datasets available for tracking rainfall and flooding, naming Worldview, the FLOOD Viewer and the GPM IMERG Global Viewer.
The article was published as part of the Earth Observatory's Image of the Day series, which was filed under the topic of floods.
What to do
- NASA says several of its tools and datasets can be used for tracking rainfall and flooding, including Worldview, the FLOOD Viewer and the GPM IMERG Global Viewer.
Key facts and where they come from
- The Gandak River rose to record levels in parts of Nepal and India after days of torrential rain.
After days of torrential rain, the river rose to record-breaking levels in parts of Nepal and India.
- Imagery came from MODIS on NASA's Terra and Aqua satellites on September 20 and September 29, 2026.
Images captured by MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra and Aqua satellites on September 20, 2026 (left), and September 29, 2026 (right), show the extent of the flooding.
- The false-color images use MODIS bands 7-2-1 so floodwater appears blue and vegetation bright green.
The false-color images combine observations of infrared and visible light (MODIS bands 7-2-1) to make it easier to distinguish the water. Floodwater appears blue; vegetation is bright green; clouds are light blue.
- A gauge in Devghāṭ hit 11.94 meters on September 27, the highest since measurements began in the 1960s.
a gauge in Devghāṭ reached as high as 11.94 meters on September 27, the highest since measurements began there in the 1960s
- Rain fell on Nepal's Lumbini and Gandaki provinces between September 24 and 27, triggering landslides.
Storms drenched Nepal’s mountainous Lumbini and Gandaki provinces with waves of torrential rain between September 24 and 27.
- NASA says Worldview, FLOOD Viewer and the GPM IMERG Global Viewer can be used to track rainfall and flooding.
NASA has several tools and datasets available for tracking rainfall and flooding. Among them are Worldview, FLOOD Viewer, and the GPM IMERG Global Viewer.