Increased River Flow abstracted no overflow Ihefu

Last Updated 4 months ago

^{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 considerable increase of irrigated area on January 2, 2023 as compared to the December 17, 2022 irrigated area is enabled by the first rains allowing more abstraction from the Mbarali and Ruaha Rivers (green and light blue colors in irrigated area). On the same day as the NBR composite image below (Landsat 8) of January 2, 2023 the drainage from the Usangu Rice Plain together with possible supplies from tributaries does not suffice yet to reach the N’giriama outlet of the Ihefu swamp.

Increased Rice Irrigation from the two main diversion weirs at Kapunga (Ruaha River and New NAFCO (Mbarali River) respectively the left and right highlighted (white) areas on the image below, seems to benefit from the increased flow in both rivers while the Drainage flow from the Usangu Rice Plain does not suffice to cross the Ihefu Swamp.

Compare the Kapunga Irrigated Area on December 17, 2022 with the image below of December 12, 2022

Usangu Rice Plain experiences very dry season 2022

It is expected that there is some more water in the Ruaha but still inadequate to launch the rice irrigation season. The 1 to 2 cumecs abstracted in Usanga for selected group of farmers (light blue and tones of green) in the highlighted (redish) Kapunga Commercial Farm would boost drainage to the water starved Ruaha National Park.

Kapunga Rice Irrigation on some few farms in total an estimated 400ha of the total 3,600ha. The image is on December 12, 2022.

Pre-crop season irrigation attempts (end of August) are doomed to fail with the early onset of the zero flow period at Usangu and Ruaha Park. Compare early rice crop on October 23, 2022 with planted crop on NBR image of August 24, 2022 (below). Also comparison with the October 29, 2019 image of Usangu Rice – Kapunga shows the dryness of 2022 due to early onset of the zero flow period.

Start Zero Flow Period Park HQ 2022 – 2023

With the start of zero flow period at Msembe Bridge (Park HQ) irrigation and spill in the Usangu Rice Plain is due to the low flow limited to mostly spill. The Kapunga Smallholder and Kapunga Commercial Scheme have been indicated and to the west spill in the uncontrolled canal network of Ifishiro also low areas with spill can be detected on August 21, 2022.

Near Infrared Sentinel-2 on August 24, 2022, with smallholder rice scheme on the left and Kapunga Commercial Farm in the center. On the right is the “informal” Ifushiro Rice Area with related spill. The difference between pre-irrigation and burnt farms can be distinguished in the image below. Click to enlarge.

The green and dark blue colors represent either rice crop, swamp and grasses from preirrigation and spill water. Dark brown areas are burned fields. The image is three days after zero flow started at the Park Headquarter at Msembe, on August 24, 2022.

Usangu Diversion and Spill August – July 2022

The use and spill of river water during the low flow period in the Ruaha River at Kapunga and Ifishiro Rice Plain and Diversion of the Mbarali River at New NAFCO Intake is monitored. The Ruaha Flow Monitor finds Irrigation and Spill hotspots and the authority will need to follow up on these hotspots. In case irrigators do not have the required permit to abstract or spill is the result of neglect both losses will be easy to recover for drainage to the park. Increased drainage during the critical low flow period (Three Alert Phases) will prevent or reduce the period of zero flow in the Ruaha Park (Park Headquarter).

With very limited time left to boost drainage before it is too late to prevent zero flow at the Park HQ, which will start within one to two weeks from now (August 11, 2022), limited resources are left, to adequately improve the low flow in the Ruaha River in the Park. Early drainage increase measures (during Alert One) will be required to delay the start of the zero flow period. With timely start of the rains and timely start of drainage management measures, zero flow can be avoided. On August 4, 2022 some spill hotspots are demonstrated using RS. (see two images below for August). For more details about the tracking down of (uncontrolled) Irrigation, Spill and Riverine “losses” click here.

Near Infrared Image of Ifushiro Area (Kapunga, Usangu Rice Plain) on August 4, 2022 shows stagnant pools bootom center and center right, the dark reds are swamp vegetation and dark brown-black are burned fields or saturated (swamp) soils. Watch Out for the dark shadows of the White Clouds. The color composite of NBR sentinel-2 images (below) is a good indicator of the spill, irrigated and riverine vegetation areas of Usangu Rice Plain. (click to enlarge)

NBR Sentinel-2 representation of the water spill areas shown in NIR image above. Dark and Light Green, Dark Blue correspond well with stagnant water, swamp vegetation (red in NIR) and saturated soils (swamp, irrigation canal leakage). Dark brown (indicate burned fields) not observed here. Clouds may leave light blue colors on NBR and need to be distinguished from atmospheric loss of ground and surface water in swamps and vegetation.

Irrigation and Spill with Alert 3 announced on July 30, 2022

Currently (July 2022) an irrigated area in the Ifushiro section of the Ruaha should be questioned already deep into the alert (phase) 2 and on the day alert alert (phase) 3 is announced.

Water is supplied by a branch of the Ruaha.

Irrigated Fields or unattended canals with crops or weed contributing to spill on the Usangu Plain during low flow in the Ruaha and Mbarali Rivers and the occurrence of zero flow due to reduced drainage from the plain on July 30, 2022. The scale fro the image is on the upper left. Compare the high resolution image below of the same area but 5 years earlier when the same phenomena of spill occured.

The same area in Ifushiro on July 24, 2017 in high resolution. (click to enlarge)

The practise of having water in the drainage system of the major rice schemes can be considered as loss as long as this water is not return flow to the Ruaha or Mbarali Rivers. Even if it the drains are used to return water to the main river channels abstraction of water from the drains should be avoided. Not only is registration and management of such diversions difficult, it also provides a precedent for illegal use of water by others. These “informal improvisations” in the system can often be associated with spill especially in the Ifushiro area where natural depressions, are likely to fill and become hotspots for spill each low flow season.