Last Updated 2 weeks ago

Drying of Ruaha River at Mtera, September 24, 2024

Last Updated 2 weeks ago

You can use the buttons to follow the time series of reduced or returning flow in the Ruaha River during the dry season of 2024-2025 at Mtera.

Alert 1 with the aim to predict the flow status upstream of the “Mtera” zero flow VDAS, one month earlier was in 2025 calculated from crossing of the ndwi threshold of 0.0134sqkm around June 10, 2025. With expected A2 zero flow on July 10, 2025. For visually (RS) observed zero flow Mtera (A2) July 16th 2025, is selected. You can find the actual drying at A2 in the interactive map.

Observations:

  1. Some 300km from the source of the Ruaha River the river dries probably already since the 1950s. The virtual usangu drainage assessment station is at Mtera some kilometers upstream of the Mtera Reservoir.
  2. On May 2, 2025 the monitor series starts and events of interest will be updated on this page
  3. Working Hypothesis – A2 Transition Zone Dynamics (ai generated)

The A2 (Mtera) observation area represents the first detectable transition from continuous river flow to fragmented surface water, characterised by stagnant pools, exposed sediments and disconnected channel sections. Owing to the low-gradient, sediment-rich morphology of this reach, the absolute residual surface-water area is expected to vary between years as channel position, sand-bar development and local pool storage evolve. Consequently, the A2 residual water area should be interpreted as a geomorphic–hydrological indicator rather than as a fixed zero-flow threshold.

Preliminary comparison with Park HQ zero-flow dates suggests that, in recent years, the disappearance of continuous surface flow at A2 has occurred approximately two months before zero flow is observed at Park HQ. Earlier observations indicate substantially longer lags. This apparent shortening of the A2–Park HQ lag may reflect accelerated recession of the Great Ruaha River and reduced persistence of surface flow. The hypothesis will be tested by extending the analysis with historical Landsat observations and by evaluating whether the observed reduction in lag is sustained over the complete satellite record.