Mauritius Reservoir Transparency

Scoped to the COVERED subset (all 7 main reservoirs). The Water Resources Unit / Water Resources Commission regularly releases fill-rate communiqués for all 7 main reservoirs (Piton du Milieu, La Nicolière, Mare Longue, Midlands, Mare aux Vacoas, Bagatelle, La Ferme), giving percent fill for each. Statistics Mauritius publishes an annual Energy & Water Digest (Nov 2024 for year 2024) including reservoir storage levels for all 7 reservoirs. However, data reaches the public through press communiqués and annual digests rather than a live self-service dashboard. The typical covered reservoir has weekly-to-monthly fill data published during normal periods, increasing to more frequent updates during droughts. Storage is reported as percent fill rather than as absolute volume in routine bulletins.

For the COVERED subset: no public REST API or machine-readable endpoint exists. The Statistics Mauritius annual Energy & Water Digest is available in Excel format with a historical series Excel file covering 1990 onwards — a meaningful structured download for a country at this development level. Operational WRU communiqués are unstructured press releases. Hydrology Data Books (covering 2000–2010) are PDF-only. The CWA GIS system (deployed 2024, ESRI) is strictly internal. Structured downloads (Excel annual digest) for 7 reservoirs combined with PDF/press release operational data is the dominant access mechanism.

Methodology v1.3.0 (capacity-weighted). Total Mauritian national reservoir storage capacity is approximately 92 hm³ across the 7 main managed reservoirs — Mare aux Vacoas (25.89 hm³), Bagatelle (~14.7 hm³), Midlands, Piton du Milieu, La Ferme, Mare Longue, La Nicolière (5.26 hm³, included as a main reservoir despite being slightly below the strict 10 hm³ threshold because it is part of national reporting). Covered capacity through WRU communiqués and Statistics Mauritius publications is the full ~92 hm³ — every main managed reservoir is systematically reported. Coverage = round(100 × 92 / 92) = 100. Minor irrigation tanks and private impoundments contribute negligible aggregate volume and are outside the operationally significant population.

MEDIAN years across the 7 covered reservoirs: Statistics Mauritius publishes a historical series Excel file (last updated Nov 2024) covering energy and water indicators from 1990 onwards, including reservoir storage levels for all 7 reservoirs — approximately 34 years of annual observations in machine-readable Excel. The Hydrology Data Books (WRU) cover monthly and daily reservoir storage variation for 2000–2010 in PDF format, providing a decade of higher-frequency historical context. The typical covered reservoir thus has 34 years of annual structured history accessible, with a decade of higher-granularity context — comfortably above the 20-year threshold. The 15-year gap in granular Hydrology Data Books post-2010 limits the score from being perfect.

For the COVERED subset: WRU/Water Resources Commission issues ad-hoc reservoir fill communiqués — multiple per month during dry-season water stress, but no confirmed fixed weekly bulletin is published on a government portal. Media reporting suggests updates at roughly weekly intervals during crises (Jan–Apr 2025), but reactive rather than systematic. The formal Statistics Mauritius annual digest is published once per year with a 12-month lag. The typical covered reservoir has irregular/event-driven updates outside crisis periods, with no daily or near-real-time public feed.

For the COVERED subset: descriptive notes on the hydrology of Mauritius and reservoir storage methodology are published in the WRU Hydrology Data Books, accessible via publicutilities.govmu.org. These documents describe the monitoring network, gauging stations index, and storage calculation methods. The WRU notes that data loggers are used at observation points. However, the methodology documents are dated (last edition covers 2006–2010), no current ISO-standard or formal methodology statement exists for the present reporting period, and WRU communiqués do not include methodology notes.

English is the primary official language of government administration in Mauritius. All Statistics Mauritius publications, the WRU website, the CWA website, and the Open Data Mauritius portal operate in English. Some WRU press communiqués and MBC news items are in French (Mauritius is bilingual), but formal statistical publications and government data portals are consistently English. International researchers face no language barrier when accessing the annual digests or the government data infrastructure.