Percolation near Bhojapur
pt-8 · 21.1590, 79.6353 · PIN 441904
Contributing catchment 4.47 km² · at a 3 m bund it impounds 108 thousand m³ over 11 ha · design monsoon yield 497 thousand m³ · soil HSG-B (clay 0%).
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 (35% of storage). Actual yield varies with monsoon reliability, seepage and siltation.
Incremental over today · the net-new gain, from the 4-year record
≈ 108 thousand m³ of net-new water · 22 ha irrigable · 1,964 drinking person-years.
full design storage — no structure holds water here today.
Why this site
Sited where soil is lighter (HSG-B) or fractures raise infiltration — a percolation tank turns runoff into recharge rather than surface storage.
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: 0.4 → 0 ha, a 0.4 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 = 0.02 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 show only a weak flow signal in the nala; nearest mapped lake is 4,511 m away.
Land acquisition (submergence)
A 3 m bund would submerge 11 ha — the land to be acquired. Cost & consent scale with this.
⚠ catchment likely includes a through-flowing nala — verify pour point
Low confidence — sensors disagree and no independent lake confirms this site. It must be ground-truthed before any commitment of funds.
Displacement witness — real building footprints
Settlement in footprint — major acquisitionIn the submergence footprint
66
buildings within the 185 m design-submergence radius (11 ha pond at 3 m).
Nearest structure
65 m
to the closest mapped building.
Within 500 m
752
buildings in the influence ring.
The design submergence overlaps a settlement — this site would require major land acquisition and resettlement, or a lower bund. Not viable at this height without displacement.
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
Bhojapur
796 m away · PIN 441904
Nearest landmark
Ganeshpur
Schools within 2 km
20
nearest 657 m
Health within 2 km
20
nearest 131 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
+0.051
47 ha lost · 223 ha gained over 1,776 ha land
Built-up (NDBI) change
18.5 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.