IGAD Food security, Nutrition & Resilience Information System

NDVI — Vegetation Conditions

Dekad (10-day) Normalised Difference Vegetation Index showing temporally smoothed NDVI and percentage of long-term mean across the IGAD region.

Overview

The NDVI (Normalised Difference Vegetation Index) module tracks vegetation health at a dekad (10-day) temporal resolution. Data is sourced from USGS FEWS NET and includes two spatial layers: the temporally smoothed NDVI and the percentage of long-term mean NDVI.

Temporal Resolution — Dekads

Data is organised by dekad — a sequential 10-day period numbered 01–36 within each year (3 per month). Dekad IDs use the format YYYYNN, e.g., 202605 = the 5th dekad of 2026 (2nd dekad of February).

Data Layers

NDVI — Temporally smoothed NDVI raster. Values range from -1 to +1; higher positive values indicate denser, healthier vegetation.
Percentage of Mean — Current NDVI expressed as a percentage of the long-term mean for the same dekad. Values below 100% indicate below-normal vegetation; above 100% indicates above-normal conditions.

Data Model

Three geographic levels are maintained:

Model	Level	Key Fields
RegionNDVI	IGAD Region	dekad, start_date, end_date, file_ndvi, file_mean
CountryNDVI	Country	country, dekad, start_date, end_date, min, max, mean
AdminNDVI	Admin Unit	admin, dekad, start_date, end_date, min, max, mean

Views Available

Map (/ndvi/map) — Interactive Leaflet map with raster overlay, dekad selector, and data type toggle (NDVI / Percentage of Mean). Includes an AmCharts 5 time-series chart for historical trends.
Data Table (/ndvi/data/) — Paginated admin-level statistics table with export to CSV and Excel. Filterable by country, admin unit, and dekad.
Upload (/ndvi/upload/) — Manual upload of two GeoTIFF files (NDVI + Mean) for a given dekad. The server clips the rasters to the IGAD boundary, compresses them, and calculates zonal statistics.

Map Colour Legend

Layer	Value Range	Colour
NDVI	0.1 – 0.2	Tan / yellow
	0.2 – 0.4	Light green
	0.4 – 0.7	Medium green
	0.7 – 1.0	Dark green
% of Mean	< 60%	Red (severe deficit)
	60 – 90%	Orange / yellow
	90 – 110%	Near normal
	> 110–140%	Blue / dark blue (surplus)

Data Collection

python manage.py collect_ndvi                     # Collect latest dekads from USGS FEWS NET
python manage.py collect_ndvi --dry-run           # Preview without saving
python manage.py collect_ndvi --dekad 202605      # Collect a specific dekad
python manage.py collect_ndvi --latest 3          # Collect the 3 most recent dekads

The command downloads seasonal zip archives from the USGS FEWS NET directory at edcintl.cr.usgs.gov, extracts TIF files, clips them to the IGAD boundary, and runs zonal statistics to populate CountryNDVI and AdminNDVI records.

Interpretation

A percentage-of-mean value consistently below 80% across multiple dekads is a strong early warning indicator of vegetation stress and potential pastoral/agricultural failure. Cross-reference with rainfall anomaly and WRSI for a composite picture.