The Zero Flow event dates are listed for the Ruaha River Sections next to the magnified remote sensing stations below. The basemap can be viewed here. The related satellite images are grouped per Ruaha River Section with the most recent images on top. The first zero flow event which occurs at the Mtera Reservoir section of the Ruaha River, can be found at the bottom of this post.

For low/zero-flow analysis of other years, please follow the link.

LabelRuaha Section LocationObservation/ 1st Zero Flow
three km. upstream of 1st Zero Flow monitor section


Few kilometers u/s of confluence Great and Little Ruaha		One month before (predicted) 1st zero flow event

August 12, 2020 (Alert 1)

September 15, 2020 Zero Flow (Alert 2)
flow returns on January 3, 2021
Ruaha River out of Park (Recession surface flow)December 4th, 2020 some 30km upstream of Mtera Reservoir (VDAS)
Msembe Bridge (National Park Headquarter)no zero flow observed in 2020 – 2021 dry season
Ruaha River 40km downstream of N’giriama Sill (Ihefu)no zero overflow observed in 2020 – 2021 dry season
N’giriama (Ihefu Swamp)no zero overflow observed in 2020 – 2021 dry season
Ruaha River Section Confluence Mbarali/Ruaha Branch- Ihefu EntryZero Drainage September 20, 2020 – November 12, 2020 and November 22, 2020 to December 3, 2020
Confluence Mbarali/Ruaha Branch Zero Flow no zero flow at Confluence
Kapunga and Mbarali Rice Irrigation Schemes Increased Rice Irrigation during zero drainage period from Usangu Rice Plain (November 2020)
New NAFCO Headworks diversion low flow MbaraliAll flow Mbarali River diverted into New NAFCO main canal in December 2020
Return Flow in Ruaharains gradually increased in November and December 2020

Mbarali River Flow Diverted in December 2020

Crest of the Weir at NEW NAFCO Mbarali Headworks exposed on December 27, 2020
Crest of weir at NEW NAFCO Mbarali headworks exposed on December 17, 2020 with all remaining low flow in the Rivewr diverted into Mbarali Main Canal.

Increased Rice Irrigation during critical zero drainage period from Usangu Rice Plain (November 2020)

The increased irrigated rice area within the blue circles on November 22, 2020, represents irrigated crop and pre-irrigation in Kapunga Commercial Rice Scheme. On November 22 also zero drainage from the Usangu Rice Plain is observed. The width of the image corresponds with some 11km. The image at the left are natural colours while the image on the right is a calculated NBR compilation – Bands 8A and 12. (Click on the image to enlarge)

Confluence Mbarali and Ruaha River Branches

Near Zero Flow at Confluence Ruaha and Mbarali Branches with drainage from Usangu Rice Plain on November 27, 2020.

Drainage Critical Flows and Zero Drainage

The analysis for the 2020-2021 low flow period in the Ruaha National Park concludes that although zero drainage did occur according to the observation below on November 29, 2020, zero overflow in the Ruaha as it flows out of the Ihefu Swamp and zero flow in the Ruaha at the Park HQ did not occur or if it occured for a few days only, which may have been missed due to the clouds blocking inspection by the monitor.

Zero (Drainage) Flow is characterised by the black refelction of the wet exposed riverbed sediments but can also resemble dark green reed blocked in the river but with flow still passing under the floating vegetation. The image above of November 29, 2020 is considered as exposed riverbed possibly with some reed combined. (click to enlarge)

The total length of the zero drainage periods is arguably estimated as two periods of in total 64 days. This could be less for days where floating reed is counted as zero flow. Important is that zero drainage did occur while no zero flow or at least negligible drying of the Ruaha River was observed in the same period of 2020. This would mean that either drainage or groundwater sources from the Ruaha and Tributaries will have sustained the flow during the shoprt critical drainage period that year. The graph below relates the maximum estimate of the zero drainage period in the Ruaha (Park) with merged satellite and gauge data for the upper reaches of the Ruaha Catchment.

Two Zero Drainage in September to November 2020 in Ruaha section between Nyaluhanga and entrance Ihefu Swamp. The drainage from the swamp and possibly local rains kept the Ruaha flowing in the Park without the two periods without drainage.
Alert 3 – Drainage drops under critical level at Nyaluhanga Gauge Station on October 23, in 2020. No evidence for zero flow at the Park HQ is found during the dry season with flow returning at Mtera on January 3, 2020.

No Overflow N’giriama Sill (Ihefu Swamp)

The first suspect observation of Zero Overflow from Ihefu Swamp on December 9, 2020 (NIR) some 8km downstream of N’giriama outlet is rejected due to absence undisputable zero overflow in the Ruaha River, 40km downstream (image below).
Distinction zero surface flow subsoil flow only with 10m/px 40km from Ihefu Overflow on December 7, arbitrary for some images, counter checks other dates and locations required.

Msembe Bridge Park Headquarter

10km upstream of the Msembe Bridge (Park HQ) probably the lowest flow in the dry season of 2020-2021 is observed in the Ruaha on December 4, 2020.

Recession Outflow Park

On December 4, 2020 recession of the Ruaha surface water flow has retreated to some 30km upstream of Mtera Reservoir where zero flow was first observed September 15th, 2020.

Mtera Reservoir

Flow returns around January 3, 2021
Alert 2 first day of zero flow in the Ruaha River at Mtera on September 15, 2020

Alert One, 1 month before predicted ZF at Mtera

Based on the calculated prediction for the zero flow at Mtera (Rainfall Sum November – March) of September 12, 2020, the First Alert is announced on August 12, 2020. Compare the flow status in the Ruaha for the section used for the Alert 1 on the left and the section used for the Zero Flow observation on the right with other years. The width of the image represents some 2.5km.