Both structures were built to hold monsoon runoff and let it soak into the aquifer. Thirty-six months of satellite measurement say one of them does exactly that — and the other has not held water once.
Sentinel-2 at 10 m, one frame per month. Turbid Malwa pond water is the same brown-green as a wet field in plain colour, so the measured water is painted blue. The second layer reads the ground itself: bare rock and soil, vegetation, water. Blank months are monsoon cloud.
Three years of water through Barkheda Kamaliya. Recharge is the water that soaked through the bed into the aquifer — the part a farmer gets back from a borewell. Evaporation is the part the sky took.
Water surface measured from Sentinel-2. The dam fills at the end of the monsoon and is empty again by February. July and August have no bar because cloud blocks the optical sensor.
SMAP (NASA, L-band, 9 km) and AMSR2 (JAXA, C-band, 10 km) both measure moisture in the top few centimetres, through cloud, every day. Both are district-scale readings around each dam, never the dam itself.
Over the 33 months where both answered at Barkheda, AMSR2 reads about 3.5× lower than SMAP (median ratio 3.48) and the two correlate only moderately (r = 0.44). L-band penetrates a crop canopy far better than C-band, which is the usual explanation for the offset — but these two instruments plainly do not substitute for one another, so both lines are drawn and neither is averaged into the other.
Esri World Imagery at 1.09 m per pixel, every distinct capture since 2022 — sharp enough to see the wall, the apron and the bed, but roughly one capture a year.
Storage change is measured; evaporation is physics; seepage is an assumed rate. What is left over is water a person took. In 23 of 26 month-pairs nothing was left over — the dam emptied at exactly the speed sun and soil explain.
| Month | Storage | Change | Evaporation | Recharge | Unexplained |
|---|
Unexplained loss is a residual: it absorbs every error in the other terms. Read it as an upper bound on pumping, not a meter reading.
Seepage is assumed at 8 mm/day — mid-range for the silty beds of Malwa check dams, and the one term no satellite measures. Every figure that depends on it scales linearly.