About Madurai Water Intelligence
An open-source water intelligence platform for Indian cities, built to make public data accessible and actionable.
Sections are collapsed by default. Click any heading to expand it.
What we track for Madurai
Madurai is governed by Madurai Municipal Corporation with civic services under Madurai Municipal Corporation (100 wards).
Water sources
Reading this dashboard
How Madurai's tap is fed today
Madurai's drinking water travels a long path before it reaches a tap: Mullaperiyar Dam (Kerala) → Periyar-Vaigai diversion tunnel → Vaigai Dam → Pannaipatty Water Treatment Plant (118.6 MLD) → Madurai Municipal Corporation distribution mains (~764 km) → 28 existing overhead reservoirs across 28 distribution zones / 81 District Metering Areas → ~95,487 connections → tap.
Two things are worth knowing when reading the dashboard's headline:
- Vaigai is a multi-purpose dam, not a city reservoir. It's owned by the Tamil Nadu Public Works Department and shared across Madurai, Theni, Sivagangai and Ramanathapuram districts for both irrigation and drinking water. MMC's sanctioned drinking-water allocation is 1,500 mcft per year - a small slice of Vaigai's total storage. The most recent reported actual draw is ~900 mcft per year (≈70 MLD continuous).
- We haven't yet found a public daily feed. Pannaipatty WTP's daily raw-water intake and treated output, the 28 existing OHTs' live levels (with 37 more being built under Tranche 2), and zone-by-zone supply are tracked inside MMC's ICCC and SCADA systems for internal monitoring; we don't have a route to a daily public surface for them today. So a single "days of water left" number for the city would be guesswork; we don't generate one.
What the dashboard does show: Vaigai's live dam level (sourced daily from the Tamil Nadu Agriculture Department's reservoir page), MMC's public allocation and recent-draw constants, and the structural infrastructure of Pannaipatty WTP and the distribution network. That's the honest version of what's currently knowable from outside MMC.
What's missing today
A few daily-operations layers aren't currently part of Madurai's public dataset. Most of these data points are tracked inside MMC's ICCC and SCADA systems for internal monitoring; they just aren't routed to a public surface yet. Listed here so users know where this dashboard's daily view ends.
If any of these become available, the dashboard can move from structural numbers (annual allocation, plant capacity) to a real measured daily runway.
Daily Pannaipatty WTP raw-water intake + treated output
Tracked inside MMC's ICCC SCADA. With a daily series, the dashboard could move from showing the allocation slice to showing actual measured throughput.
Per-DMA supply across the 81 District Metering Areas
DMA-level supply telemetry isn't in the public dataset today. 42 DMAs are covered via earlier 24x7 + Smart City Mission rollouts; ADB Tranche 3 covers the remaining 39, with 115 newly-established DMAs targeted post-build. With this telemetry the dashboard could surface which neighbourhoods are getting served daily and which lean on tankers and borewells.
OHT-wise live storage (23 overhead reservoirs)
Aggregate existing-OHT capacity (41.05 MLD across 28 OHTs per IEE Part 2) is documented per-tank in `madurai-supply-overview.json`; per-OHT live levels live in MMC's SCADA. Per-OHT readings would let zone-level supply gaps surface in near real time.
Non-revenue water and per-capita supply (LPCD)
MoHUA's Service Level Benchmarks set targets (135 LPCD, 20% NRW). We haven't yet found Madurai-specific actuals against these targets in any open dataset. Pey Jal Survekshan (which Madurai is a pilot city for) computes LPCD internally; we haven't found a public city-level scorecard.
PWD-WRD daily Vaigai drinking-water release log
Daily drinking-water release volumes from Vaigai are reported episodically through news during release events (Chithirai pulses, summer ~200 cusec drinking baseline) but not as a structured feed. A daily series would let the dashboard's allocation view reflect real seasonal variation rather than a static constant.
In flight: ADB Investment Program IEE / DPR parse
The ADB Tamil Nadu Urban Flagship Investment Program Tranches 2 and 3 contain engineering-grade tables for Madurai distribution zones, OHT capacities, and demand projections to 2046. Parsing those PDFs once is the next planned data unlock for the dashboard - converts the allocation hero into a zone-reliability heatmap.
Default consumption assumptions (Madurai)
Madurai-specific defaults used to compute days-of-water-left. These are conservative starting points; the dashboard exposes sliders so users can substitute their own.
| Parameter | Default | Source / note |
|---|---|---|
| Daily city demand | 135 MLD | Madurai Corporation operational estimate; ~85 MLD piped supply across 100 wards. |
| Desalination contribution | 0 MLD | No desal plants commissioned for Madurai. |
| Groundwater contribution | Excluded from days-left | Borewells supplement the piped supply but exact MLD is unmodelled. CGWB block + ward-level depth views show groundwater stress separately. |
| Reservoir evaporation | Not modelled | Vaigai / Mullaperiyar evaporation is non-trivial in summer; planned for v2 once a daily ET0 series is wired. |
Users can adjust consumption and desalination values via sliders on the dashboard.
What each page shows for Madurai
Home / dashboard
The home page anchors Madurai's reservoir picture. Vaigai dam (the drinking-water source) is the headline; Mullaperiyar (Periyar reservoir in Idukki, Kerala) is the upstream feeder via the 1886 lease tunnel and contributes ~80% of Vaigai's annual yield.
9-year history chart
Daily storage and percent-FRL trends going back to 2018, sourced from TN Agriculture's public reservoir archive. Toggle between 90 days, 1 year, 3 years, and the full archive; toggle Vaigai vs Mullaperiyar independently.
14-day forecast
Each reservoir gets its own AutoARIMA fit. Seasonal differencing kicks in once we have at least two years of history; the forecast is shown as a dashed continuation line plus a shaded 80% confidence band. Refits daily as new readings land.
- Each reservoir is forecast independently - no cross-source pooling.
- The model retrains on every refresh; we don't freeze parameters.
- 14-day horizon is aggressive but useful; the 80% band widens as you go out.
- Predictions clamp at 0 and the registered FRL capacity per source.
Groundwater
Madurai's groundwater page combines two authoritative views: CGWB block exploitation (the official annual classification across the district) and a 3-factor ward-level risk composite (composite_score - gw_depth - wb_density - wb_health). The map also shows the CGWB Year Book point network as click-through markers for direct depth readings at known wells.
Block exploitation (GWR)
11 CGWB-classified blocks across Madurai district (Madurai East/North/South/West, Melur, Peraiyur, Thirupparankundram, Tirumangalam, Usilampatti, Vadipatti, Kallikudi) coloured by the latest annual draft-percentage from CGWB's Dynamic Ground Water Resources assessment. Status classes: Safe / Semi Critical / Critical / Over Exploited.
CGWB Year Book point overlay
21 monitoring stations from CGWB's Ground Water Year Book of Tamil Nadu & Puducherry (2023-24 and 2024-25 editions) - peer-reviewed, manually-measured dug wells in the phreatic / unconfined aquifer. Each station carries quarterly depth-to-water-level readings (May / Aug / Nov / Jan) spanning May 2023 - January 2025. Click any marker for the well's hydrograph and full reading history. Stations are tagged with their CGWB block (Alanganallur, Chellampatti, Kallikudi, Kottampatti, Madurai East, Madurai West, Melur, Sedapatti, T.Kallupatty, Thirumangalam, Thirupparankundram, Usilampatti, Vadipatti).
Why no per-ward depth choropleth?
We deliberately do NOT publish an IDW-interpolated ward depth choropleth for Madurai (the way Chennai does, via OpenCity's monthly per-ward survey data). The four India WRIS live stations across the entire district are too sparse to produce an honest 100-ward choropleth; spreading those four points smoothly across the city would manufacture precision we don't have. The 21 CGWB Year Book stations + the 11-block exploitation classification together give an honest picture without faking ward-level granularity that the underlying data doesn't support.
Live India WRIS station overlay
We also drop markers for each India WRIS live station in Madurai district. Click a marker for the well's metadata (acquisition mode, depth, aquifer type) and recent reading window. As of latest scrape, Madurai district has 4 telemetric (DWLR, daily) and minimal manual stations - much sparser than Chennai's ~35-station network.
Ward risk composite
A 3-factor weighted percentile score per ward, A-F graded. Chennai uses 5 factors (drainage 25%, sewerage 25%, flood 25%, WB-health 15%, WB-density 10%); Madurai's drainage / sewerage / flood-hazard GeoJSON layers don't exist publicly yet, so v1 ships a reduced composite with what we have:
| Factor | Weight | Direction |
|---|---|---|
| Groundwater depth (IDW) | 50% | Deeper = higher risk |
| Water-body density (per sq km) | 20% | Denser = lower risk |
| Water-body health (mean restoration_priority within 3 km) | 30% | Higher score = sicker tank = higher risk |
Each factor is converted to a city-wide percentile (0=best, 100=highest risk), weighted, and summed. Composite ≤20 = A, ≤40 = B, ≤60 = C, ≤80 = D, >80 = F.
Water bodies
715 water-body polygons across Madurai district, sourced from OpenStreetMap. Click any polygon for its tags; the 19 hand-curated flagship tanks carry extra metadata (status, area, builder/era, court-order anchors).
Vaigai mainstem polygons are explicitly labelled - a post-process matches each unnamed river polygon to the nearest section of the Vaigai polyline within 500 m, so long stretches of the river are no longer left blank on the map.
The lake-restoration narrative (lost tanks, flagships, programmes, court orders) lives on its own page rather than the map view; jump in via Lake restoration.
Rivers
Vaigai-system scope: 304 km Vaigai mainstem, 67 km Periyar (Kerala feeder, to the Mullaperiyar dam), 72 km Suruliyaru, 40 km Manjalar, 41 km Varaha tributaries. Per-river sidebar shows length, status, upstream/downstream termini, and feed.
CPCB monitoring stations
Vaigai is on CPCB's Priority III polluted-stretch list. Two stations on the National Water Monitoring Programme cover the Madurai stretch - one upstream of the city, one downstream - with annual readings for dissolved oxygen, BOD, pH, conductivity, fecal coliform, and nitrate. We extract those readings from CPCB's annual River Water Quality reports (2021-2024 covered today) and show them as a per-station table when you select Vaigai in the sidebar.
Markers are colour-coded by the latest BOD reading: red above 6 mg/L, amber above 3, green at or below 3, grey when no readings exist. The four other Vaigai stations a journalist might expect (Vaigai dam, Andipatti, Manamadurai, Ramanathapuram) stay grey because CPCB doesn't monitor them today.
Court orders & key events
A hand-curated event log filtered to the selected river. Today it covers the Madras HC's December 2024 suo motu cognisance of Vaigai pollution (177 sewage / industrial discharge points across 5 districts, sampled stretches graded unfit even for irrigation), the Supreme Court's 2014 Mullaperiyar verdict (142 ft storage cap, still-active Supervisory Committee), and the operational threshold around Vaigai dam release that triggers Madurai-city flood warnings (about 6,000 cusecs).
Industrial pollution sources
Six hand-curated Vaigai-basin polluters mapped as type-coloured markers: the SIDCO industrial estates at Kappalur and K. Pudur, the Sellur sewage discharge zone, the Dindigul tannery cluster, the Theni textile dyeing units, and the multi-district outfall inventory cited in the December 2024 Madras HC order. Compiled from TNSIDCO records, the DHAN Foundation CURE study, the Columbia GSAPP Madurai studio, NGT orders, and news reporting. The Tamil Nadu Pollution Control Board's online effluent monitoring portal (OCMMS) is referenced as the live cross-check.
Flood risk
Narrative-only stub. Hazard-zone polygons (5/10/25/50/100/200-year return periods), historical flood-hotspot layers, drainage GeoJSON, and sewerage overlays don't exist publicly for Madurai (in contrast with Chennai's OpenCity-published layers). The page surfaces the Vaigai dam-release threshold (~6,000 cusecs as Madurai-city flood warning; 12,000+ during the 2018 floods) and a documented locality risk note pending RTI to Madurai Corporation.
Lake restoration
Madurai-only narrative-rich page (Chennai redirects /lake-restoration to /water-bodies). Sections: 14 lost urban tanks, 12 severely-reduced tanks, 19 hand-curated flagships, restoration programmes (Kudimaramathu / AMRUT / Smart City / IAMWARM), Madras HC court-order anchors, DHAN partnership target.
Restoration priority badge
Each flagship carries a colour-coded priority badge built from four signals:
- Status severity 0-80 - drying / lost > severely reduced > encroached / polluted > restored.
- Cultural bonus 0-35 - Biodiversity Heritage Site (+25), Ramsar candidate (+20), HC PIL anchor (+15), pre-1700 heritage (+10), dynasty-era (+8).
- Size 4-25 - acres bucketed (very large / large / medium / small / tiny).
- Source confidence ×0.7-1.0 - V (verified), N (newsroom), C (claim only) downweights.
Sum is bucketed: ≤40 low, ≤60 moderate, ≤80 high, >80 critical. First run produced 5 critical, 2 high, 7 moderate, 5 low. Top 5: Vandiyur 100, Thenkal Kanmoi 100, Madakulam 88, Avaniyapuram 85, Samanatham 80.
My Ward / Report Card
Ward-boundary map for Madurai Corporation's 100 wards (5 zones, 2022 delimitation). Click a ward to see zone, area, centroid, and a link into the per-ward report card.
Per-ward report card
Each report card shows a large A-F grade badge, the composite score out of 100, the ward's rank within the city, and a per-factor breakdown (raw value, percentile, weight). Without a specific ward selected, the page renders an index grouping ward chips by grade so you can jump straight to the worst-graded wards.
Madurai's report card is intentionally slimmer than Chennai's. Chennai's is built on a 5-factor composite plus an uplift-planner cost matrix; that costing layer is out of scope for the Madurai launch because the underlying drainage and sewerage layers aren't published.
Water facts
Journalist-ready quotable stats grouped by freshness tier - live (this season), derived (last 12 months), historical (documented), and heritage (pre-modern). Today Madurai ships 14 hand-curated heritage and governance facts plus 9 auto-derived stats that compute from the data layers we ship: over-exploited blocks, critical and semi-critical blocks, restoration priority counts, F-grade ward count and worst ward, citywide interpolated groundwater depth, Vaigai BOD pollution gradient, Vaigai dissolved oxygen downstream, urban tank area lost.
Intelligence & AI narratives
Daily AI briefings, longer-form weekly narratives, and per-ward AI profiles are pending for Madurai - the underlying summary stores aren't yet multi-city. Until those land, the page surfaces raw data without an AI commentary layer.
Lake catchment atlas methodology - Madurai
The cascade overlay answers "which tank drains into which". The catchment atlas answers the prior question: where does each lake's water come from. Every lake sits at the bottom of a catchment - the land whose rain drains toward it. Click any lake on the Catchments view and we draw its area of influence: the catchment polygon, the feeder streams inside it, the tanks upstream and downstream, and where its overflow finally reaches a river.
What you are seeing
- Orange (solid): the lake's own / direct catchment - the land that drains straight into it before reaching any other tank.
- Amber (dashed): the inherited basin upstream - catchment that drains in via other tanks. Own + inherited = total upstream basin.
- Blue lines: feeder streams, width graded by Strahler order (trunks thicker than first-order rills).
- Violet dotted line: the downstream flow path - how the lake's overflow actually runs through the channel network, lake by lake, until it reaches a river.
Inputs
- Elevation: FABDEM (Forest And Buildings removed Copernicus DEM) at 30 m. This is a bare-earth surface - buildings and tree canopy are removed - so water routes over the real ground rather than over rooftops, which matters in dense urban terrain. (The cascade graph uses coarser 90 m HydroSHEDS; the atlas deliberately uses the finer DEM.)
- Lake polygons: OpenStreetMap
water=*features, the same set the water-bodies map uses. - Buildings: Overture Maps building footprints, for the rooftop-harvest estimate.
- Rainfall: India Meteorological Department (IMD) long-period annual normals for the district.
How the catchment is delineated
- Mosaic FABDEM over the district (buffered so edge catchments close), then condition it with WhiteboxTools
breach_depressions_least_cost(preferred over fill in cities - it preserves channels running under roads and culverts). - Compute D8 flow direction and flow accumulation; extract a stream network and assign Strahler order; vectorise the streams and smooth them (Chaikin corner-cutting) so they trace the natural curved channels rather than blocky raster steps.
- For each lake, trace the contributing area upstream from its footprint. The own (direct) catchment is the upstream trace that stops at the next water body - the land draining to this lake before any other tank intercepts it. Removing that barrier gives the total upstream basin; the difference is the inherited area. This is threshold-free: there are no impound-vs-transit tuning knobs.
- Downstream: from the lake's outlet (its highest-accumulation boundary cell) follow the channel by always stepping to the highest-accumulation neighbour until it enters another water body; chaining those hops along the cascade gives the full downstream flow path to the river.
- Rooftop harvest: clip Overture footprints to the own catchment, then
rooftop area × annual rainfall × 0.8(0.8 runoff coefficient), reported in million litres per year.
Naming the lakes and rivers
- OpenStreetMap names many water bodies but leaves a large share unnamed (in Madurai the OSM gap is substantial). Where an authoritative open dataset exists - for Bengaluru, the ATREE/CSEI named-lake census published on OpenCity - we attach the real toponym by polygon overlap and tag it
name_sourcewith a match confidence. OSM-native names are never overwritten, and a small pond sitting inside a large lake's outline is not given that lake's name (a wrong name is worse than a blank one). - The river a lake drains into is named by snapping its downstream flow path to the nearest mapped river (within 0.5 km). Lakes whose path stays far from any named river - because they flow off the edge of our coverage - honestly show no named river rather than a guess.
What this is NOT, and known limits
- Not a substitute for a surveyed catchment. A 30 m bare-earth DEM resolves urban catchments well but misses sub-cell culverts, storm drains, and engineered diversions that move water against the natural terrain.
- Bounded by our map extent. A lake near the edge can drain to a reservoir or river outside the area we model (for example a southern Bengaluru tank flowing toward the Krishnagiri reservoir, which is off-map). We trace the flow path correctly but cannot name a sink we do not hold.
- Rivers are conduits, not catchments. Named rivers/canals are excluded as lakes; very elongated polygons with a huge catchment-to-area ratio (river segments mis-tagged as water bodies) are filtered out.
- Rainfall is a long-period normal, not the actual rainfall of any given year, so rooftop-harvest figures are a typical annual potential, not a measured yield.
- Backfilled names are a join, not ground truth. They carry a source tag and a match confidence; treat low-confidence matches as provisional.
Data sources for Madurai
All operational data is collected by the Python pipeline and supporting scripts that power the dashboard. Raw source data and Earth Engine summaries are upserted into Supabase (PostgreSQL) and then exposed as small, readable product signals.
Reservoir & weather
Daily storage, level, inflow and outflow for Vaigai and Mullaperiyar (listed as Periyar) on a state-wide page. The same site serves a dated archive back to 2018, which we use to backfill the 9-year history chart.
Engineering-grade structural numbers extracted from the December 2025 ADB Initial Environmental Examination Parts 1-3 + Tranche 3 IEE: 192 MLD existing supply mix across 7 schemes (Vaigai surface 115 + Vaigai sub-surface 47 + Cauvery via Melur 30); Pannaipatty WTP 118.6 MLD existing (71.6 Line-I + 47.0 Line-II) / 243.6 MLD planned post-Tranche 2; 28 existing OHTs (12 N + 16 S, 410.5 LL aggregate) plus 37 new under Tranche 2; 28 distribution zones / 81 District Metering Areas (42 today + 39 in Tranche 3 scope; 115 newly-established post-build); 764 km existing mains + 813 km new under Tranche 3; 95,487 connections (94,487 dom + 600 non-dom + 400 com), targeting 163,958 households; 2034 demand 317 MLD; PWD allocation table (MMC 51.09 cusecs continuous). Powers the dashboard's at-a-glance tile.
MMC's published 1,500 mcft/year drinking-water allocation from Vaigai with ~900 mcft recent draw. Infrastructure stats on the public page differ slightly from the engineering IEE values (page lists 23 OHTs, 96,048 connections, 467 km mains, 81 distribution zones) - we treat the IEE Parts 1-3 as the primary engineering record and document the disagreements in `madurai-supply-overview.json._secondary_local_source`.
14-day forecast with 80% confidence band per reservoir, refit daily as new readings land. Seasonal differencing kicks in once we have at least two years of history.
Free, no-auth weather data, ECMWF / ERA5-Land base. Used here for rainfall: its archive API fills the months IMD's gridded series hasn't published yet - rendered as asterisked provisional months that IMD supersedes automatically.
India Meteorological Department 0.25-degree gridded rainfall, 1970-2025. Madurai grid cell at 9.9 deg N, 78.0 deg E, 862.6 mm long-term mean. Same imdlib pipeline as Chennai's IMD generator.
51 Madurai neighbourhood points (Anna Nagar, Pasumalai, Mattuthavani, KK Nagar, Sellur, Vandiyur, etc.) extracted from OpenStreetMap for the my-ward search box. 49/51 carry Tamil names. Powers locality-name -> ward resolution.
Groundwater
Annual block-level Dynamic Groundwater Resource Assessment (Safe / Semi Critical / Critical / Over Exploited). 11 blocks classified across Madurai district (Madurai East/North/South/West, Melur, Peraiyur, Thirupparankundram, Tirumangalam, Usilampatti, Vadipatti, Kallikudi).
Peer-reviewed quarterly depth-to-water-level readings (May / Aug / Nov / Jan) at 21 dug-well stations in Madurai district, sourced from the 2023-24 and 2024-25 Year Books. Replaces an IDW-interpolated ward depth choropleth - Madurai's live WRIS network is too sparse (4 stations) for honest per-ward synthesis. Stitched into a 2-year per-station time series.
Water bodies & restoration
Base geometry for water-body polygons and the rivers polyline.
14 fully lost and 12 severely reduced urban tanks - roughly 16.5 sq km of combined area, around 30% of the old city's footprint.
19 hand-curated flagship tanks and dams with status, area, builder / era, and court-order anchors. Powers the restoration-priority composite.
Each flagship is scored on status severity (0-80) plus a cultural-heritage bonus (0-35) plus a size bucket (4-25), then scaled by a source-confidence multiplier between 0.7 and 1.0.
Hand-curated rows for the Kudimaramathu, AMRUT, Smart City, and IAMWARM programmes plus the Madras HC anchors that have shaped restoration policy.
Rivers & pollution
Annual River Water Quality reports (2020-2024 covered today). Vaigai is monitored at two stations - upstream and downstream of Madurai - with min and max readings per parameter; we use the midpoint.
December 2024 suo motu order naming 177 sewage and industrial discharge points across 5 districts, sampled stretches graded unfit even for irrigation, and a state-government action plan due January 2025.
May 2014 Constitution Bench permitted 142 ft Mullaperiyar storage and struck down Kerala's 2006 cap. Established a permanent Supervisory Committee that still arbitrates seasonal storage and dam-safety reviews.
Six hand-curated polluters: SIDCO Kappalur and K. Pudur estates, Sellur sewage discharge zone, Dindigul tannery cluster, Theni textile dyeing units, and the multi-district outfall inventory cited in the December 2024 HC order.
The Tamil Nadu Pollution Control Board's real-time monitoring portal for red-category industries. Cross-check reference for the curated sources list.
Field study finding 8 of 9 Vaigai sampling spots unfit for human use across physical, chemical, and biological parameters. Underpins the qualitative status notes in the rivers and lake-restoration narratives.
Flood & civic infrastructure
Hazard zone polygons (5, 10, 25, 50, 100, 200-year return periods), historical flood hotspots, drainage and sewerage networks - none of these are publicly published for Madurai today. Tracked as follow-up RTIs.
Satellite & remote sensing
Per-water-body wet/dry history from satellite. Pipeline ready; data layer pending for Madurai's 19 flagships.
Weekly water-spread readings for 9 Madurai water bodies (6 tanks and 3 dam reservoirs), shown in each one's water-body panel against its usual spread for the season. NDWI thumbnails and change detection are still pending.
Catchment polygons for Vaigai dam and its sub-basins, used to ground catchment-rainfall context. Pending wiring for Madurai.
Base geometry & AI
AI city narratives and per-ward profiles. Pending for Madurai.
Data quality & limitations
How we classify river health
CPCB publishes two parallel river-water-quality classification systems, and they don't always agree. Knowing which one we use - and why - matters for reading our river status badges honestly.
Designated Best-Use classes (A-E)
Computed from current dissolved-oxygen, BOD and coliform thresholds at each monitoring station. Updates every reading. Class A = drinking with disinfection only; Class B = outdoor bathing; Class C = drinking with conventional treatment; Class D = fisheries/wildlife; Class E = irrigation only. Below E = practically dead.
Polluted River Stretch (PRS) Priority I-V
A historical, multi-year stretch-level designation reflecting cumulative pollution. Slow to update; once a river stretch is on the Priority list it tends to stay there even if recent readings improve. Priority I = worst (BOD > 30 mg/L sustained); Priority V = least bad of the polluted stretches.
Our status badges ("dead", "severely degraded", "degraded", "stressed", "healthy") are computed from current readings via the Designated Best-Use thresholds - not from the PRS Priority list. We take the worst classification across a river's monitored stations and surface that as the river-level status.
Practical consequence: a river on CPCB's PRS Priority list (e.g. the Madurai-Manamadurai stretch of the Vaigai is Priority III) won't automatically render as "severely degraded" here. If the underlying NWMP readings show only Class C/D conditions, the badge reflects that. The PRS designation belongs in the river description as historical context, not as the live status.
Status thresholds follow CPCB's published Designated Best-Use criteria; readings are from CPCB NWMP annual River Water Quality reports.
Open data gaps in Madurai
Some layers we'd like to surface aren't publicly released yet for Madurai. We've listed each one with the workaround currently in place; tracked as RTI follow-ups where applicable.
No public flood-hazard return-period layer
Standard 5/10/25/50/100/200-year flood return-period polygons are not currently published for Madurai. The flood-risk page falls back to a narrative-only view anchored on the 6,000-cusec Vaigai dam-release threshold; 2018 floods peaked above 12,000.
No public drainage / sewerage GeoJSONs
Drainage line and sewerage main GeoJSONs aren't publicly released - tracked as RTI follow-ups to Madurai Municipal Corporation. The ward risk composite ships a 3-factor variant (water bodies, lost bodies, groundwater) until those layers land.
CPCB monitors only 2 of the 6 candidate Vaigai stations
NWMP covers Vaigai U/S Madurai (10059) and D/S Madurai (10060). Vaigai dam, Andipatti, Manamadurai, and Ramanathapuram are seeded for future expansion but stay readings-empty.
No per-ward depth choropleth (deliberate)
Madurai district has only four India WRIS live groundwater stations - far too sparse to honestly interpolate a 100-ward choropleth. Instead we surface 21 CGWB Year Book point stations as the depth signal, alongside the 11-block CGWB exploitation classification. The IDW-interpolated view used in earlier drafts has been retired.
Lost-tank coordinates not populated
The 26 Vencatesan / DHAN documented lost tanks have name + status but no lat/lng - geocoding historical tank names is research-heavy and most have no OSM presence (they're lost). Listed as a Tier 3 follow-up.
Known Limitations
- Source feeds may occasionally be stale (weekends, holidays, portal outages). Each surface shows a freshness indicator.
- Groundwater data may lag by months or years. The map always shows the most recent available period.
- Forecasts use AutoARIMA on each reservoir's daily storage alone (no inflow or outflow inputs) and work best with 2+ years of daily data.
- Risk scores are relative indicators for comparison between wards, not absolute measures of water safety.
- Satellite spread is a summary of surface water extent, not a direct measure of storage volume, water quality, or inflow source. A lake can look broad and still hold less usable water than expected.
- Current satellite context relies on optical Sentinel-2 observations. During persistently cloudy periods, some water bodies may temporarily lose this insight until a radar fallback is added.
Documented lost urban tanks (Vencatesan + DHAN)
About the project
Disclaimer
Not an official government tool. Neer Vazhvu is an independent, open-source project. It is not affiliated with, endorsed by, or connected to any water utility, municipal corporation, pollution control body, or other government agency whose published data it cites.
Informational purposes only. All data, estimates, and forecasts are provided “as is” for general awareness. Always refer to official advisories from your city's water utility and disaster-management authorities for critical decisions.
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Open Source
Neer Vazhvu is fully open source. The code, data pipeline, and methodology are transparent and available on GitHub. Contributions, bug reports, and data corrections are welcome.
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