The newest post and image entries are on top of the page. Scroll from the bottom upwards to follow the flow status timeline of the Ruaha River per location

The sporadic rains and delay of the seasonal rains resulted in a new dry spell and zero flow in the Ruaha at Mtera during the end of December 2023. Although cloud cover in January 2024 reduces the reliability of the observations it is expected that around January 8, or following days the flow at Mtera has recovered. Images some 82km upstream of the VDAS of Mtera shows increase of flow on 20m pixel Sentinel composite (Land and Water Band Red8, SWIR1, Red).

Flow increase some 82km upstream of VDAS Mtera on January 8, 2024. (Click to enlarge)
Flow status during zero flow at Mtera 82km downstream at same section of the Ruaha as image at left. The section is 12km downstream of Msembe Bridge at Park HQ. (Click to enlarge)

Ruaha dries again at Mtera

After the flow returned in the Ruaha River from local rains it dried again in the absence of sustained seasonal rains in the upper reaches of the Ruaha and Mbarali River Catchments. The flow status of the Ruaha at the Alert 2 VDAS River section, shows the remaining pools in the drie riverbed.

Ruaha River at Mtera on December 24, 2023 after it dried again following a small recovery as the result of local rains. Only sustained seasonal rains will show sustained drainage from the Usangu Rice Plain reach the Mtera Reservoir during the first half of the year.

End zero flow period Ruaha at Mtera

On December 6, 2023 the water front in the Ruaha has reached at least 20 km from the VDAS at Mtera, according to the nearest Landsat 7 image. As all landsat satellites cross the equator in the morning hours, it is estimated that on December 6, 2023 the flow returned at Mtera.

2km section Ruaha River at Mtera on December 4, 2023 with dry riverbed. (Click to enlarge)
Flow in Ruaha has returned at Mtera on December 9, 2023. (Click to enlarge)

Alert Two

Zero flow at Mtera is observed on August 26, 2023. Alert phase two is declared for reduction of non essential abstractions from the Mbarali and Ruaha Rivers on the Usangu Plains. The images in the slider below include the pre-zero flow status of the Ruaha River at Mtera on August 21, 2023 and the first day on which zero flow is observed (August26, 2023).

Flow Mtera 20230821 Zero Flow Mtera 20230826
Observation of zero flow at Mtera on August 26, 2023. The width of the 5m/px Sentinel color infrared composite image is 1.3km. Compare the Ruaha River section with the image below of August 21, 2023. (Click to enlarge)

New Procedure Low Flow Analysis (remote flow monitor)

For the development of standards for low flow analysis, the sentinel L2A band 8 is selected. To replicate the natural environment of the flow the Ruaha River channel is extracted by the normalised difference water index (NDWI). The result of this new procedure is demonstrated in the image slider below. The resampled 5m pixels are compared with the color infrared composite from EOS of August 21, 2023.

The Ruaha riverbed with sandbanks deeper pools and flow channels (darker blue). The blue-greyish flow pattern is shallow flow channels to subsurface flow. Groundtruth may further improve the analysis. The 5m/px image is taken on August 21, 2023. The width of the image is 4.4km. (Click to enlarge)

Alert One

The period July 27, 2023 and August 8, 2023 had some cloudy days which may have delayed the occurrence of Alert One with one week or more. Alert One is now announced on August 8, 2023. Compare the Landsat 7 images of one month before zero flow at Mtera in 2022 and 2023.

Landsat 7 the color manipulated image has a resolution of 30m/px resampled to 5m/px expaining the blurred image of the Ruaha at Mtera on August 8, 2023
The Landsat 7 image one month before occurrence of zero flow at Mtera on July 11, 2022 compares well with the image on the left. (Click to enlarge)

Flow Ruaha River at Mtera July 27, 2023

Flow in Ruaha River on July 27, 2023, (Click to enlarge)

Flow Detail “Alert 1 Section” Ruaha River July 22, 2023

Flow in Ruaha River on July 22, 2023
Compare Flow at Alert 1 one month before drying Ruaha River at Mtera in 2022. (June 17)

Flow Detail “Alert 1 Section” Ruaha River July 17, 2023

Compare the flow on July 17, 2023 with the flow status in the Ruaha one month before the first zero flow observation at Mtera in 2022. The two magnified river sections are respictively from July 17, 2023 and June 17, 2022 which latter flow was recorded one month before the drying of the river. It suggests that zero flow is not expected before the second half of August in 2023.

Ruaha River at Mtera on July 17, 2023
The flow in the same Ruaha River section on June 17, 2022. One month before drying of the river at Mtera.
The flow in the Ruaha River section some kilometers upstream of the Mtera reservoir on July 17, 2023. The yellow circle indicates the magnified section with 5m pixels. The width of the magnified bend in the river is approximately 100m.

Flow on July 12, 2023

Increased exposure of riverbed and decreasing surface flow in the Ruaha River at Mtera on July 12, 2023. (Click to enlarge)

Flow on June 27, 2023

Flow in Ruaha River at Mtera on June 27, 2023 (Sentinel 2). (Click to enlarge)

Flow on June 20, 2023

Landsat 8 image on June 20, 2023. Flow in Ruaha River at Mtera continuous. (Click to enlarge)

Flow on June 17, 2023

Flow at two Alert monitor sections Ruaha River on June 17, 2023. WIdth of image is 2.5km. (Click to enlarge)

Flow Comparison Mtera

One cloudless section of the Ruaha some 2 km long as the bird flies, is compared on June 7, for four years, with 2020 some days later on the 11th of June.

The upper image had the first occurrence of zero flow on July 17, 2022 and the lowest image the last occurrence on September 15th, 2020. According to the current flow status in 2023 the predicted zero flow occurrence this year is between July 17 and August 31. Successful intervention in the regulation of additional drainage from the Usangu Rice Plain may postpone the occurrence of zero flow at Mtera.

Last year 2022, the flow in the Ruaha at Mtera on June 7, was clearly much less with large stretches of river bottom sediments already exposed. Zero flow last year was first observed on July 17, 2022.
Flow in Ruaha this year 2023 on June 7, looks comparable to the flow in 2021, though slightly less. Zero flow expected July/August. Interventions by the water authority may push the occurrence of zero flow beyond September as in 2020.
Flow in Ruaha section on June 7, 2021 upstream of Alert monitoring section. In 2021 zero flow at Mtera on August 31, 2021.
Flow status in the Ruaha on June 11, 2020 upstream of the Alert monitoring sections. In 2020 zero flow at Mtera occured on September 15th 2020. (Click to enlarge)

Status Flow Mtera June 2, 2023

On June 2, 2023 the Mtera Ruaha sections for spotting the start of Alert 1 (left) and the season’s first Zero Flow (Alert 2) are still swollen with water. The width of the image is 2.5km. (Click to enlarge)

Status Flow Mtera May 18, 2023

The Ruaha River just upstream of the confluence with the Little Ruaha is still swollen without signs of the upcoming dry season and drying of the river at the selected section of the Great Ruaha which dries first every year.

The near infrared image of May 18, 2023 shows about 2km (width of image) of the Ruaha River which is swollen with flood plain full of swamp vegetation (red) and filled pools.