India Reservoir Transparency

The CWC weekly bulletin publishes, for the ~166 strategic reservoirs, a complete per-reservoir record: live storage (BCM), live capacity at FRL, full reservoir level (FRL) and current level (m), percent of capacity, and last-year and 10-year-average comparison columns — released as a structured weekly PDF. Direct retrieval (Jun 2026) confirms the current national bulletin is published weekly on rsms.cwc.gov.in (e.g. bulletin-04-06-2026, 166 reservoirs) and the free cwc.gov.in archive holds the weekly back-run to 2023. State portals add granular daily data for several states. Publication completeness/granularity of the covered set is high.

The data is retrievable but poorly open. The dominant channel is a weekly PDF bulletin, and there is NO documented open API — the current bulletins on rsms.cwc.gov.in are reachable only by resolving the host out-of-band (the portal's listing speaks an undocumented AES-enveloped endpoint) and the whole CWC/rsms estate is geo-restricted to Indian IPs (non-Indian/datacenter IPs fail to resolve/connect). So while the PDFs themselves are not auth-gated (they return HTTP 200, no login — correcting an earlier mis-finding of '401'), an international consumer cannot obtain them without an Indian IP and bespoke tooling. data.gov.in's open CWC dataset stops Dec-2023. Mechanism: geo-restricted PDF, no open API.

v1.3.0 capacity-weighted. The CWC national bulletin covers ~166 strategic reservoirs ≈ 183.5 BCM of India's ≈257.8 BCM national capacity (~71%), and direct retrieval (Jun 2026) confirms this data IS obtainable and current — the giants previously written off as 'no data' all carry a 04-06-2026 reading: Indira Sagar (12,221) 21%, Rihand (10,600) 28%, Bhakra/Gobind Sagar (9,868) 30%, Sardar Sarovar (9,460) 48%, Pong (8,570) 35%, Ukai (8,510) 38%, Hirakud (8,141) 19%, Gandhi Sagar (7,322) 62%, Tehri 0.4%. Adding the non-CWC reservoirs served by state portals (Andhra Pradesh, Telangana, Karnataka, Kerala, Bihar, Tamil Nadu), reservoirs with obtainable current data sum to ≈234,000 hm³ ≈ 88-91% of national live storage. The remaining gap is small/medium reservoirs outside both the CWC set and the state portals.

A continuous structured weekly series is obtainable from 2023 to the present for the covered set — the free cwc.gov.in archive holds ~2 years of weekly bulletins (2023-06 → 2025-05) and rsms.cwc.gov.in continues the run to date, giving ≈3 years of accessible weekly history per strategic reservoir. The bulletins additionally embed a 10-year-average comparison column, implying a deeper internal archive, but that longer series is not exposed as a structured download. Median accessible depth across the covered capacity is therefore moderate (~3 years).

CWC publishes a national bulletin every week and the current week is available (bulletin dated 04-06-2026 retrieved Jun 2026); the covered strategic reservoirs are therefore refreshed weekly. State portals (Andhra Pradesh, Telangana daily; Kerala, Bihar, Tamil Nadu daily/near-daily) refresh their subsets even more often. Weighted by capacity, the typical covered reservoir is updated weekly — the main caveat is that the freely-international channel (cwc.gov.in archive page) lags the current rsms release.

The bulletins expose live capacity at FRL, FRL and current reservoir level (m), regional/state groupings and date, and the National Register of Large Dams provides per-dam structural metadata — so the headline quantities and their definitions are documented. What is not consolidated in any openly accessible form is the measurement methodology (gauging, stage-storage/area-capacity curves, sedimentation re-surveys), uncertainty estimates and QC procedures. Documentation of the figures themselves is good; documentation of how they are produced is thin.

English is an official working language of the Indian government and is used across the CWC bulletin and the state portals (with regional-language toggles), so language is not a barrier. Usability is still held back by delivery — a dense multi-page PDF rather than a queryable interface, and the geo-restriction that keeps the current national channel off-limits to international users without an Indian IP.