Satellite data for water quality and algal bloom monitoring in Australia
By Mazdak Ghasemi · Last checked 22 October 2026
Which satellite data is best for monitoring water quality and algal blooms?
Optical imagery of the water surface. Sentinel-2's 10 m and 20 m bands suit lakes, rivers and near-shore water, and ESA notes it lets scientists analyse water within 2 km of the coast. Sentinel-3's OLCI, with 21 bands at about 300 m, suits large water bodies and the coast. In Australia, satellite chlorophyll is still largely experimental: Digital Earth Australia treats its Sentinel-2 chlorophyll index as experimental, and CSIRO is building its AquaWatch system.
Which data to use
| Data | Resolution | Revisit | Record | Use |
|---|---|---|---|---|
| Sentinel-2 | 10 m; red-edge bands 20 m | 5 days | From June 2015 | Chlorophyll and turbidity in lakes, rivers and near-shore water |
| Sentinel-3 OLCI | About 300 m, 21 bands | Under 2 days with two satellites | Ocean-colour series | Large lakes, coastal and ocean water |
| Landsat 8 and 9 | 30 m | 16 days each, 8 together | From 2013 | Turbidity and a longer record |
| DEA Water Observations | 30 m | Updated daily | From August 1986 | Where water is, not its quality |
How it is done
- Use atmospherically corrected imagery and mask cloud and sun glint.
- Calculate an index for the property you need; Digital Earth Australia's experimental chlorophyll index (NDCI) uses Sentinel-2's red-edge 1 and red bands.
- Check against water samples before relying on the values.
Limits to know
- EUMETSAT notes that only about 10% of the light a satellite measures over water in blue and green comes from the water itself, so atmospheric correction is critical.
- Coastal and inland waters are optically complex: dissolved organic matter and suspended sediment make chlorophyll harder to measure than in open water.
- Sun glint can still affect images, even from sensors designed to avoid it.
- Satellites measure what is at or near the surface, and not every rise in a chlorophyll index is an algal bloom (DEA).
Who does this in practice
- Digital Earth Australia publishes a chlorophyll monitoring notebook using the experimental NDCI on Sentinel-2.
- CSIRO's AquaWatch Australia is co-designing and building a national ground-to-space water quality monitoring system.
What Terrascout returns
The real result for “Monitor algal blooms and turbidity in the Gippsland Lakes VIC” (Gippsland Lakes, VIC), captured on 22 October 2026: the top 3 of 6 sources.
| # | Source | Type | Resolution | Cost | Fit |
|---|---|---|---|---|---|
| 1 | Sentinel-2 MSI | Optical | 10 m | No data fee | 97 |
| 2 | Landsat 8 OLI/TIRS | Optical | 30 m | No data fee | 90 |
| 3 | Landsat 9 OLI-2/TIRS-2 | Optical | 30 m | No data fee | 90 |