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ALERT 1 GEE-TimeSeries Script on July 21, 2026

The forecast model (2026) has a threshold of 0.010sqkm2 which is crossed today. Comparison of the various forecast methods also include the linear regression forcast based on 2025-2026 non-overlapping periods and predicts June 28, 2026 as Alert1 date. The visually inspected zero flow at the Mtera VDAS will reveal the most accurate method.

Alert 1 for 2026 started June 23

The 2025 Google Earth Engine (GEE) workflow identified 0.012 km² as the historical Alert 1 reference threshold from seven years of Sentinel-2 observations.

During 2026, Sentinel-2 NDWI reached this threshold on 21 June (0.01204 km²) and declined below it on 23 June (0.01086 km²), providing the first observed satellite evidence of Alert 1 conditions. Sentinel-1 SAR indicated an earlier decline between 4 and 5 June, but because SAR has a coarser spatial resolution and serves primarily as an operational backup during periods of persistent cloud cover, the Sentinel-2 NDWI observations are retained as the principal observational reference.

The operational Alert 1 forecast used by the Alert1 pipeline is generated independently from the A1_best_area prediction model. The observed Sentinel-2 threshold crossing is therefore used to evaluate model performance and timing, rather than to define the forecast itself. Check the interactive graph, “Ruaha River flow drops to ALERT 1 in 2026”. June 23, 2026 is adopted as first observed Alert 1 date.