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From Town Tools. For the current version, visit https://www.towntools.org/maun-north-west-district-bw/catching-the-rain
Litres this roof catches each month of a typical year. The rains do the work in a few months — storage carries you through the dry ones. The rains here come November–March.
JanJan: 6,700 L
FebFeb: 4,900 L
MarMar: 3,200 L
AprApr: 816 L
MayMay: 96 L
JunJun: 96 L
JulJul: 0 L
AugAug: 0 L
SeptSept: 144 L
OctOct: 480 L
NovNov: 2,500 L
DecDec: 4,800 L
And right now
About 18 mm of rain has fallen in the last 30 days — enough for this roof to have caught roughly 850 litres.
These are estimates, not a promise
The catch is plain arithmetic from your roof size and average rainfall — real water depends on your roof, gutters, the first wash thrown off a dusty roof, and how big a tank you have to hold it. Treat it as a starting point for sizing a tank, not a guarantee.
Maun's piped supply has been short for years: Water Utilities Corporation has put the town's demand at roughly 15 million litres a day against about 9.9 million supplied, and the P3.6 billion upgrade meant to close that gap is still unfinished. Rain is the one supply nobody rations.
Live rainfall from Open-Meteo (CC BY 4.0) — a weather-model estimate for the area, not a rain gauge on your street. Updated .
Rain off a roof is not drinking water
Water off a roof is NOT safe to drink as it comes. Dust, bird droppings and debris wash in with it. It is genuinely useful as it is for washing, cleaning, flushing, the garden, livestock and building — and it saves the piped or bought water for drinking. To drink it, treat it: filter it, then disinfect it by boiling or with household bleach at the dose on the bottle. A first-flush diverter and a mesh screen on the tank inlet make a large difference.
Rainfall varies a lot around here
Maun's rain arrives in one short season — November to March — and almost nothing falls from May to September, so storage, not rainfall, is what decides how much you actually use. These are typical-year figures from a weather model for Maun's area, not a promise for your roof, and the year-to-year swing here is very wide: over the thirty rain-years to 2020 the middle year brought about 460 mm, the wettest about 890 mm, and the driest — 2018/19 — only about 190 mm, a bit over a third of normal. Size a tank for a thin year, not an average one. What has actually fallen in the last 30 days is shown further down.
What goes into the numbers
Why not every drop is caught
Not all the rain that lands on a roof reaches the tank. Gutters miss some, the first wash off a dusty roof is best thrown away, and a full tank overflows in a big storm. The sums here keep about 80% of the rain, which suits a corrugated-iron, tile or concrete roof. Thatch catches much less and is hard to gutter.
How much water a person uses
The "days of water" figure assumes about 25 litres per person per day — enough for drinking, cooking and washing, not for a garden or a yard tap left running. It is a way to picture how far a tank goes, not a limit anyone should be held to.
Worth knowing
Throw the first wash away
By the time the first storm of the season arrives in November, a Maun roof has had six or seven dry months of dust on it. That first run-off carries the worst of it. A first-flush diverter sends a set amount down the drain before the rest goes into the tank, and it does it on its own once fitted.
The tank is the whole trick
Nearly all of Maun's rain falls in about five months. A roof that catches plenty in January is catching nothing at all in August, so what you can use across the year is set by how much you can hold, not by how much falls. Work out the driest stretch you need to cover and size backwards from there.
Keep it covered, and keep mosquitoes out
An open drum in the yard breeds mosquitoes and collects whatever blows in. A sealed tank with a screened inlet and a screened overflow stores water for months without either problem. It also stops evaporation, which in Maun's heat takes a surprising amount off an open surface.
It also takes the load off the yard
Rain caught on the roof is rain that is not running across the plot and into the sand around the foundations during a heavy December storm. Guttering into a tank is drainage as well as supply.
Where to get help
Water Utilities Corporation (WUC)The town's piped supply. WUC publishes no live rationing schedule for Maun — report a fault through their offices, or the number on your bill.
Government of BotswanaMinistry and department contacts, including the water and sanitation portfolio.