El Nino Watch
Weekly NASA maps of groundwater and soil-moisture drought over Asia.
Data and trust
The GRACE-FO satellites weigh the water stored on land by measuring tiny changes in Earth's gravity. NASA Goddard blends this with a land model and the University of Nebraska's Drought Mitigation Center publishes weekly maps. The app keeps the Asia maps: shallow groundwater, root-zone soil moisture and surface soil moisture.
Limits. The model spreads GRACE's coarse (~300 km) measurement to 0.25 deg, so small islands like Samui are not resolved. Maps are posted weekly (Monday date).
Colours are wetness percentiles compared with 1948-2012: dark red = drier than 98 % of past weeks (2nd percentile), red <= 5, orange <= 10, tan <= 20, yellow <= 30, white 30-70 = normal, light to dark blue = wetter than normal.
El Nino droughts empty soils and aquifers over months. On 2026-09-21 the map showed much of Thailand and Indochina in the red/dark-red classes. Groundwater drought lasts long after the rains return and matters for Samui's water supply.