Check dam near Wahani
cd-15 · 21.4528, 79.8613 · Tumsar taluka · PIN 441915
Contributing catchment 89.73 km² · at a 3 m bund it impounds 188 thousand m³ over 20 ha · design monsoon yield 33,307 thousand m³ · soil HSG-D (clay 41%).
In plain words
The most promotable of the surveyable check dams — a site near Wahani (Tumsar) on an 89 km² catchment where the two sensors track the monsoon flow well (correlation 0.76) and the surrounding land is stable. Six buildings fall inside the 3 m submergence footprint — the lightest land question of the check-dam candidates.
What to build
Survey the six structures and verify the pour point, then build a check dam / nala bund if they clear.
Why here
Good sensor agreement and a real catchment make the water case sound; the two open questions are the six structures and the usual large-catchment check — that the reach is a harvestable nala rather than a through-flowing river.
How
Cadastral (7/12) overlay and ground survey of the six structures; confirm the pour point and whether the flow is local catchment or through-flowing.
The delta — now vs after
A clean survey moves Wahani onto the build list — new monsoon storage and protective irrigation with only a light land question to settle.
What it delivers · indicative
Indicative benefit at a 3 m bund (DEM area-capacity at 3 m bund) under standard norms (irrigation ~5 TCM/ha; drinking 150 lpcd). Recharge is limited on HSG-D clay (12% of storage). Actual yield varies with monsoon reliability, seepage and siltation.
Incremental over today · the net-new gain, from the 4-year record
≈ 188 thousand m³ of net-new water · 38 ha irrigable · 3,418 drinking person-years.
full design storage — no structure holds water here today.
Why this site
Sited on an order-4 nala with a 89.7 km² contributing catchment and gentle grade — a nala/check dam impounds monsoon runoff on the clay lowlands where infiltration is low.
Seasonal water extent · dual-sensor
Radar (S1, 48 passes) fills the monsoon gap that cloud hides from optical (S2, 37 scenes). Radar peak vs summer low: 16.6 → 0 ha, a 16.6 ha annual draw-down — the storage renovation recovers.
Area-capacity (DEM, 30 m) · gross storage by bund height
Cross-witness & confidence — independent corroboration
Two sensors track together
Optical (S2) and radar (S1) rise and fall together with correlation r = 0.76 across 37 paired months. Absolute extents match 0% — they differ by sensor physics on a flowing nala, so the shared rhythm is the witness, not the magnitude.
Nala flow (new-build site)
No existing lake here — expected for a new structure. Sensors confirm a monsoon flow pulse in the nala; nearest mapped lake is 8,296 m away.
Land acquisition (submergence)
A 3 m bund would submerge 20 ha — the land to be acquired. Cost & consent scale with this.
⚠ catchment likely includes a through-flowing nala — verify pour point
Displacement witness — real building footprints
Several structures — survey neededIn the submergence footprint
6
buildings within the 253 m design-submergence radius (20 ha pond at 3 m).
Nearest structure
92 m
to the closest mapped building.
Within 500 m
46
buildings in the influence ring.
Overture Maps buildings 2026-05-20.0 (union of OSM / Google Open Buildings / Microsoft / Esri), Bhandara admin_code=506. A desktop displacement screen — precedes, not replaces, cadastral (7/12) verification.
Reconnaissance context & access — Ola + Google Places
Nearest habitation
Wahani
731 m away · Tumsar taluka · PIN 441915
Nearest landmark
Wahini
Schools within 2 km
0
Health within 2 km
1
nearest 653 m
Google Places (New) searchNearby + Ola Maps Places nearbysearch · reconnaissance-grade. Independent witness to the buildings displacement layer — dense amenities near a site corroborate high displacement. Does not replace cadastral 7/12 records, geotechnical bores or a level survey.
Human pressure — land-cover change (2022 → 2026)
Stable land coverVegetation (NDVI) change
+0.04
46 ha lost · 123 ha gained over 1,835 ha land
Built-up (NDBI) change
26.3 ha
new built-up / bare (construction proxy)
Window
2022-11..2023-02 (8 scenes)
→ 2025-11..2026-02 (8 scenes)
Sentinel-2 L2A dry-season MEDIAN composites (2022-23 vs 2025-26), water-masked; NDVI+NDBI change screen — not cadastral or DEM cut/fill
DPR-grade desktop hydrology from Copernicus GLO-30 (30 m) + ISRIC SoilGrids + ESA WorldCover; water extent from Sentinel-2 L2A MNDWI (optical) and Sentinel-1 GRD VV radiometrically calibrated to σ⁰ (DN²/sigmaNought² from the product calibration LUT, GCP thin-plate-spline geocoded, open water at σ⁰ < −17 dB; thermal-noise floor not subtracted). A desktop assessment that precedes — not replaces — the statutory ground & geotechnical survey.