H1 2026 Evaluation
Tanzania Reservoir Transparency
F8Opaque — Ranked #116 out of 167 countries
weight 30%
weight 20%
weight 15%
weight 13%
weight 10%
weight 8%
weight 5%
Primary source evaluated
TANESCO — Tanzania Electric Supply Company (power plant pages)
https://www.tanesco.co.tz/generationDimension breakdown
Data Availability
20% of total score
No institution publishes current reservoir storage volumes or water levels for Tanzania's major hydropower reservoirs online. TANESCO's website lists static plant descriptions for Mtera (3,200 Mm³ capacity, 80 MW) and Kidatu (125 Mm³), but contains no operational readings. EWURA's annual Water Utilities Performance Reports cover urban water supply utilities, not hydropower reservoirs. The Ministry of Water (maji.go.tz) maintains a Water Point Mapping System and MajiIS portal focused on rural water supply; its water resources sub-page links to informational Swahili text rather than data. The Julius Nyerere HPP (2,115 MW, all nine turbines commissioned April 2025) has no published reservoir storage data. The most recent public hydrological yearbook covers 2010–2019, published as a PDF with no current data.
Technical Accessibility
15% of total score
There is no public REST API, no open data download, and no machine-readable format for reservoir storage data from any Tanzanian authority. The open data portal (opendata.go.tz) has historically hosted around 100 datasets dominated by education and population data — none related to reservoir storage. The World Bank's Tanzania TANESCO Power Systems dataset (last updated 2018) is a GeoJSON of infrastructure locations, not operational data. The Ministry of Water's MajiIS and Maji Dashboard portals are internal government systems requiring login. DAHITI satellite altimetry covers some Tanzanian water bodies but is a third-party academic tool, not an official national source. No scraping of operational data is feasible as there is no data published.
Coverage
30% of total score
Tanzania has 776 dams and reservoirs with a combined capacity of approximately 5,462 Mm³. The four dominant hydropower reservoirs — Mtera (3,200 Mm³), Kidatu (125 Mm³), Julius Nyerere / Stiegler's Gorge (design reservoir of ~34,000 Mm³), and Kihansi — account for the vast majority of economically significant storage. None of these publish current storage data online. Lake Victoria levels are jointly monitored with Uganda and Kenya but data is not routinely attributed to Tanzania's share in a public Tanzanian portal. The Rufiji Basin Water Board does not publish reservoir fill bulletins. Coverage of publicly accessible operational data is effectively zero for all significant reservoirs.
Historical Depth
13% of total score
The Ministry of Water published a Hydrological Year Book covering January 2010–December 2019 as a PDF — the most recent machine-readable (though non-structured) historical record publicly available. It covers river flows and lake levels across major basins including Rufiji, but does not present reservoir storage volumes in tabular machine-readable form. No successor volume for 2020 or later has been identified. Academic studies (e.g. DFID-funded HR Wallingford Mtera-Kidatu modelling reports from the 1990s) document historical operations but are not maintained as living datasets. A data gap of at least six years (2019–2025) exists for any published hydrological record from official sources.
Update Frequency
10% of total score
No periodic or real-time data publication exists for Tanzanian reservoir storage. EWURA produces annual regulatory reports (most recent covering 2023/24) but these concern urban water supply utilities only. TANESCO publishes no operational bulletins for reservoir levels. The Ministry of Water's hydrological yearbook has not been updated since the 2010–2019 edition. Tanzania received eight new Nile Basin Initiative hydrological monitoring stations in early 2025 (on Mara, Kagera, Grumeti, and other rivers), but data from these stations is telemetered to internal national and regional data centres without confirmed public-facing publication. Tanzania's National Energy Compact (World Bank, 2025) requires EWURA to publish annual KPI reports from 2027 onwards — reservoir storage is not an explicit obligation.
Methodological Transparency
8% of total score
No public document describes how TANESCO or the Ministry of Water measures reservoir storage or water levels at Mtera, Kidatu, or Julius Nyerere HPP. TANESCO's principal operations engineer has stated in press interviews that Mtera's full supply level is 698.5 m and minimum operating level is 690 m, but this is a journalistic source, not a formal methodology document. The Ministry of Water has published technical guidelines for drinking water quality monitoring and basin fact sheets, but these do not cover surface reservoir storage measurement protocols. International assessments (Winrock Tanzania Country Profile 2021, CIWA drought resilience profile) note that Tanzania's hydrological monitoring network is underequipped and partially non-functional at many stations.
Language and Usability
5% of total score
TANESCO's website is in English and provides English-language static descriptions of its hydropower plants. EWURA's regulatory reports are published in English. The Ministry of Water homepage (maji.go.tz) is primarily in Swahili, though some PDF publications are bilingual. Most donor-funded assessments (World Bank, FAO, Winrock) that describe Tanzania's water sector are in English. However, since operational reservoir data is essentially absent from all public sources, language accessibility is a secondary obstacle — the minimal score reflects that what little is published (static plant pages, regulatory reports) tends to be available in English, which is the one modest positive.
Evaluator notes
Tanzania presents a stark transparency deficit despite holding some of the most consequential hydropower reservoirs in sub-Saharan Africa. The Mtera reservoir (3,200 Mm³ on the Great Ruaha River) has triggered repeated national power crises when water levels fall — most severely in the early 2000s and again in recent drought years — yet no real-time or even monthly reservoir fill data is publicly accessible. The Julius Nyerere Hydropower Project (2,115 MW, all nine turbines commissioned April 2025), the largest hydropower facility in Africa south of the Sahara by installed capacity at completion, has created a reservoir of approximately 34 billion m³ on the Rufiji River, but TANESCO publishes no operational storage data for it whatsoever. EWURA's regulatory mandate currently extends to urban water supply utilities rather than hydropower reservoir oversight, and the World Bank–backed National Energy Compact (2025) requires EWURA to publish annual performance KPIs starting 2027 — reservoir transparency is not an explicit obligation in that framework. The Ministry of Water's institutional capacity for hydrological monitoring exists on paper: Tanzania operates 362 hydrological stations, maintains a Hydrological Year Book series, and in early 2025 received eight new telemetric monitoring stations from the Nile Basin Initiative. However, the most recent publicly available Hydrological Year Book covers only through 2019, and the MajiIS and Maji Dashboard internal portals are not publicly accessible. The water resources section of maji.go.tz returns informational Swahili text rather than downloadable data. Tanzania's open data portal (opendata.go.tz) has never hosted reservoir storage datasets; its roughly 100 catalogued datasets are dominated by education and population statistics. The overall picture is a country where hydropower vulnerability is well-documented and nationally significant — TANESCO historically derived up to 40% of generation from the Mtera-Kidatu cascade — yet institutional reform since 2019 has focused on expanding generation capacity (Julius Nyerere HPP) rather than data publication. Meaningful improvement would require TANESCO to publish at minimum a monthly reservoir operations bulletin with levels and storage volumes, and for EWURA's regulatory scope and mandate to explicitly cover hydropower reservoir reporting. Both steps appear technically feasible given existing monitoring infrastructure but are absent as of the 2026 evaluation date.
Evaluated by Jaime Delgado · 2026-09-15 · Methodology v1.3.0