Sites › Dhaka City
Urban inland · 300 km to the Bay of Bengal
Dhaka City
LOCAL eutrophic blooms dominate. Coastal plankton intrusion is essentially irrelevant at this distance.
Geometry and setting
- Centroid
23.78660 N, 90.42350 E- Bounding box
90.33718,23.66957,90.50989,23.9037- Extent
- 17.6 x 26.0 km
- Polygons
- 1
- Administrative
- Tejgaon thana polygon, Dhaka district (GADM level 3)
- Water bodies
- Hatirjheel, Gulshan/Banani/Dhanmondi/Ramna/Crescent lakes · Buriganga, Turag, Balu, Shitalakshya rivers · Tongi Khal · thousands of ponds
- Trophic state
- Hyper-eutrophic. Heavy untreated sewage and industrial load. Dense, persistent cyanobacterial blooms.
- Health data
- icddr,b Dhaka Hospital (Mohakhali), ~20,000 cholera patients/yr, 2% systematic sample
- Ocean colour
- regional forcing only (reg_ prefix)
Share of days with a real observation
Before any gap filling. Planning
estimates — 11_algae_daily_fill.py measures the true figure for your AOI.
2000–20145%
2015–20169%
2017–202622%
Dhaka is the problem case. Roughly 5% of days
observed before 2015 — Landsat at 16 days is the only sensor that works here. A daily series for
2000–2014 would be about 95% invented. Model that era monthly, or restrict the daily
analysis to 2017 onward.
Algae variables that apply here
| Variable | Family | Formula | Lag (wks) | Panel column | Why it is here |
|---|---|---|---|---|---|
| MNDWI | (B3 - B11) / (B3 + B11) |
|
Water mask. Defines WHERE to measure algae each pass. Better than NDWI in built-up Dhaka. | ||
| TURBIDITY | B4 / B3 |
|
Both a covariate and a QUALITY FLAG - extreme sediment loads corrupt chlorophyll retrievals. | ||
| BLOOM_AREA | bloom extent | fraction of the water mask exceeding a chlorophyll or FAI t… |
2-8 | bloom_frac_ndci, bloom_frac_scum |
Bloom EXTENT and FREQUENCY are more epidemiologically meaningful than a mean concentration. |
| NDCI | chlorophyll | (B5 - B4) / (B5 + B4) |
4-8 | ndci, ndci_max, ndci_wmax |
The red-edge index. Works in TURBID productive water where blue-green ratios (OC4) fail - i.e. every water body at all three of your sites. |
| PHYCOCYANIN | cyanobacteria | B3 / B5 |
2-8 | phyco_proxy, phyco_620, cyano_frac |
THE HIGHEST-NOVELTY VARIABLE IN THIS PROJECT. Phycocyanin is the CYANOBACTERIA-SPECIFIC pigment. Islam 2007 showed V. cholerae survives inside the m… |
| PHENOLOGY | derived | bloom initiation date, peak date, duration, amplitude, inte… |
seasonal | derived downstream |
Racault argues bloom TIMING carries more cholera signal than bloom magnitude. High novelty, cheap to derive once you have the time series. |
| FAI | scum | B8 - (B4 + (B11 - B4) * (842 - 665) / (1610 - 665)) |
2-6 | fai, fai_wmax |
Floating Algae Index. Baseline subtraction in the NIR · robust to aerosol, thin cloud and sun glint. Detects SURFACE SCUM, which chlorophyll indices … |
Datasets at Dhaka City
| Verdict | Code | Product | Reliability | Resolution | Cadence | Coverage | Cost | Note for this site |
|---|---|---|---|---|---|---|---|---|
| YES | AL03 |
Sentinel-2 MSI Level-2A (harmonised) | A+ Gold | 10 m (B2,3,4,8) / 20 … |
5 days (2-3 d with S2C from 2… | 2015-06 (L1C) / 2017-03 (L2A) → present | FREE | HIGHEST VALUE — the ONLY sensor that sees Hatirjheel, Gulshan Lake and the Buriganga |
| YES | AL05 |
Landsat 5 / 7 / 8 / 9 Collection 2 Level-2 | A+ Gold | 30 m |
16 days per satellite (~8 d w… | 1984 (L5) / 1999 (L7) / 2013 (L8 → present | FREE | ESSENTIAL for 2000-2015 |
| YES | AL14 |
Harmonized Landsat Sentinel-2 (HLS) v2.0 | B Usable | 30 m |
2-3 days combined | 2013 (L30) / 2015 (S30) → present | FREE | HIGH |
| YES | AL18 |
Sentinel-2 Level-1C + ACOLITE Dark Spectrum Fitting | B Usable | 10-20 m |
5 days | 2015-06 → present | FREE (both) | THE RIGOROUS ROUTE for urban lakes |
| YES | AL19 |
GEE Sen2Cor L2A NDCI → chlorophyll polynomial | C Caution | 10-20 m |
5 days | 2017-03 → present | FREE | SCREENING ONLY |
| YES | AL20 |
Landsat green/blue chlorophyll proxy (2000-2015 backfill) | C Caution | 30 m |
16 days | 1984 → present | FREE | USE WITH EXPLICIT CAVEAT |
| YES | AL22 |
SeaBASS — NASA bio-Optical Archive and Storage System | D In-situ | Point |
Per cruise/campaign | 1980s → present | FREE | Unlikely |
| YES | AL23 |
GLORIA — Global Reflectance community dataset for Imaging… | D In-situ | Point |
Per sample | 1980s → 2021 | FREE | HIGH — includes hyper-eutrophic waters |
| YES | AL24 |
LIMNADES — LIMnology and remote sensing Network dataset | D In-situ | Point |
Per sample | 1980s → present | FREE (data-sharing agreement) | HIGH — the largest phycocyanin in-situ archive · essential if you pursue cyanobacteria |
| PARTIAL | AL09 |
Copernicus Global Land Service — Lake Water Quality (LWQ3… | A Reliable | 300 m (LWQ300) / 100 … |
10-day composite | 2016 (LWQ300) → present | FREE | CHECK COVERAGE — Dhaka's lakes may be too small for the 300 m mask |
| PARTIAL | AL10 |
ESA CCI Lakes v2.x | A Reliable | 1000 m |
DAILY | 1992 → 2020 (v2.0.2 … | FREE | MEDIUM — a consistent 28-year record IF Dhaka's lakes are in the mask |
| PARTIAL | AL04 |
Sentinel-3 OLCI — 21 bands incl. 620 nm (phycocyanin) & 7… | A+ Gold | 300 m full resolution |
~1-2 days (S3A + S3B) | 2016-10 → present | FREE | MARGINAL — only the widest reaches of the Buriganga and the largest lakes |
| PARTIAL | AL17 |
IRI Data Library (Ingrid) — the portal you started from | B Usable | varies by dataset |
Daily / pentad / monthly | varies (some back to 1850s) → present | FREE | MEDIUM — same |
| PARTIAL | AL25 |
Bangladesh Oceanographic Research Institute (BORI) / Dept… | D In-situ | Point |
Varies | 2000s → present | LIKELY PAID or requires an MoU | MEDIUM |
| PARTIAL | AL26 |
icddr,b environmental microbiology archives (Huq et al. 2… | D In-situ | Point (pond) |
FORTNIGHTLY | ~2000 → varies | FREE for collaborators | MEDIUM |
| NOT APPLICABLE | AL06 |
MODIS-Aqua Level-3 SMI | A Reliable | 4.6 km |
Daily / 8-day / monthly | 2002-07 → present | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL07 |
SeaWiFS Level-3 SMI | A Reliable | 9 km (4 km avail.) |
Daily / 8-day / monthly | 1997-09-04 → 2010-12-11 (m… | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL08 |
VIIRS SNPP / NOAA-20 chlorophyll (NOAA CoastWatch) | A Reliable | 4 km (750 m for some … |
DAILY | 2017 (SNPP) / 2019 (N20) → present | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL11 |
Copernicus CDS — Satellite Ocean Colour (OC-CCI repackage… | A Reliable | 4 km |
Daily / monthly | 1997-09 → present | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL12 |
CMEMS Global Ocean Biogeochemistry Reanalysis | A Reliable | 0.25 deg (~28 km) |
DAILY | 1993 → present (roll… | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL01 |
ESA Ocean Colour CCI v6.0 — merged multi-sensor chlorophy… | A+ Gold | 4 km (1 km regional a… |
Daily / 5-day / 8-day / MONTH… | 1997-09 → 2024/25 (roll… | FREE | NOT APPLICABLE — 4 km, 300 km inland |
| NOT APPLICABLE | AL02 |
Copernicus Marine GlobColour — L4 gap-free multi-sensor c… | A+ Gold | 4 km |
DAILY (gap-free!) | 1997-09 → present | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL13 |
MODIS-Terra Level-3 SMI | B Usable | 4.6 km |
Daily / 8-day / monthly | 2000-02-24 → present | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL15 |
PACE OCI — hyperspectral 380-900 nm at 5 nm | B Usable | ~1.2 km |
1-2 days | 2024-04 → present | FREE | NOT APPLICABLE |
| NOT APPLICABLE | AL16 |
MODIS MOD09GA/GQ daily surface reflectance (250-500 m) | B Usable | 250 m (b1,b2) / 500 m |
DAILY | 2000-02-24 → present | FREE | NOT APPLICABLE — every Dhaka water body is sub-250 m |
| NOT APPLICABLE | AL21 |
OCTS / CZCS historical ocean colour | C Caution | 9 km |
Daily/monthly | 1978 (CZCS) / 1996 (OCTS) → 1986 / 1997 | FREE | NOT APPLICABLE |