How to tell an abandoned borehole from a working one in satellite imagery

Desk review before you drive out

A WASH officer planning coverage for an under-mapped district usually starts with a list of GPS points pulled from an old survey, a health post logbook, or a donor's as-built records. Half of those points might be dead by now. The question is which half, and you'd rather answer that from a desk than from four hours on a motorbike.

Satellite imagery at 0.3 m resolution or finer shows the structure around a borehole: the headworks, the apron, the tank stand if there is one, the footpath worn into the ground by people fetching water every day. It does not show whether the pump handle still turns or whether the casing ran dry last year. Functional status is a field call. What the imagery gives you is a shortlist of where to send someone first.

Visual cues that separate an active point from a dead one

A working borehole usually has a visible wear pattern around it: a packed-earth apron where buckets and jerry cans sit, a footpath converging from the nearest cluster of houses, sometimes a drainage line where spilled water has cut a small channel off the slab. If there's a tank stand, check whether the tank is actually sitting on it. A tank pulled for repair or never replaced leaves an obvious gap in the frame.

A derelict point tends to read the opposite way. The apron is still there in the image, concrete doesn't vanish, but the footpath has faded or disappeared because nobody walks it anymore. Vegetation creeps onto the slab in a way it never does on an apron that gets swept and used daily. If there was a tank stand, sometimes only the bare frame remains, a detail easy to miss at a glance and obvious once you're looking for it.

Timing changes the contrast too. One pass captured near the end of dry season, when every working point in the district has heavy foot traffic, makes active and abandoned points look very different from each other. A pass taken right after the rains, when households are drawing surface water anyway, can make even functioning points look quiet.

What the imagery alone can't tell you

None of this replaces someone standing at the headworks. A point can look abandoned from above and still work fine, maybe a new path formed too recently to weather into the ground, or the handpump got repaired last month and the area around it hasn't picked up a visible pattern yet. The reverse happens too: a point with a worn apron in last year's imagery can fail the week before your team arrives. The imagery tells you where to look first. It doesn't tell you what you'll find when you get there.

That's the actual use of a point inventory built from imagery. Instead of walking the whole district on guesswork, or starting from a ten-year-old spreadsheet, you cross-reference your old GPS list against what's visible in a current pass, flag the points showing wear and the ones that look dormant, and send your field team to confirm the dormant ones before spending a week re-checking points that were probably fine. Sanitation Mapping builds that kind of point inventory from one annual VHR pass over your district, dated and located, so the cross-reference starts from something current instead of last year's field notes.

A quick desk checklist

Before anyone drives out, mark each point from the old list against three things you can usually answer from the image: is there a visible apron or slab, is there a worn path leading to it, and if there was a tank stand, is the tank still on it. Points that fail two out of three go to the top of the visit list. Points that pass all three can wait their turn.

If that's the kind of triage you need before sending a field team out, that's what Sanitation Mapping runs once a year over your district.