What a roof in Bandipur could catch in a typical year, which months would fill a tank, and how many days of household water that is — with how much rain has actually fallen in the last 30 days.
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From Town Tools. For the current version, visit https://www.towntools.org/bandipur-gandaki-province-np/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 June–September.
JanJan: 980 L
FebFeb: 932 L
MarMar: 1,400 L
AprApr: 3,100 L
MayMay: 8,000 L
JunJun: 13,400 L
JulJul: 18,500 L
AugAug: 15,000 L
SeptSept: 8,100 L
OctOct: 2,500 L
NovNov: 404 L
DecDec: 636 L
And right now
About 303 mm of rain has fallen in the last 30 days — enough for this roof to have caught roughly 12,100 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.
Bandipur sits on a ridge with no river and no spring at the top. Every litre that reaches the bazaar is pumped or piped up from lower down, which is why the Tin Dhara taps are still in daily use and why the supply thins out in the dry months before the monsoon. Rain is the one water the ridge gets for free — about 1,824 mm of it a year, though two-thirds arrives between June and September.
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
Roof rain is not drinking water as it comes off the roof. It picks up dust, bird droppings and leaf litter, and a monsoon that starts after a dry spell washes the worst of it down first. Divert the first few minutes of every storm away from the tank, keep the tank covered and screened, and filter and disinfect — boiling, or a proper filter with chlorination — anything you or your family will drink. For washing and for the toilet it is fine untreated.
Rainfall varies a lot around here
These are typical-year averages for the area, not a measurement of your roof or a promise about this year. Two things are worth knowing before you size a tank. First, rain varies sharply over short distances in hill country — the ridge, the Dumre road below it and the outer wards do not all get the same rain on the same day. Second, the published climatologies for this area disagree: the FAO/JICA figures used here total 1,824 mm a year, while the ERA5 reanalysis for the same area over 1991–2020 comes out near 2,345 mm. The lower figure is used deliberately, because over-estimating what a roof will catch is the mistake that leaves a tank empty.
What goes into the numbers
Why not every drop is caught
Assumes a hard roof — corrugated iron sheet, tile or concrete — with gutters in reasonable order. About a fifth of the rain that lands is lost to splash, gutter overflow in heavy monsoon downpours, and the first-flush water you throw away. A thatched or badly guttered roof catches considerably less.
How much water a person uses
Counted at 45 litres per person per day, the basic service level Nepal's rural water-supply guidelines design village systems around (bazaar systems are designed at 60). It covers drinking, cooking, washing and sanitation. Many households on the ridge get by on less, especially in the dry months — so if your own use is lower, the water will stretch further than the figure below.
Worth knowing
The dry months are the problem, not the wet ones
Roughly two-thirds of Bandipur's rain falls in the four monsoon months. November through March get under 40 mm a month between them, and the pre-monsoon stretch from February to May is when ridge-top supply is thinnest. A tank sized only to catch a good monsoon downpour will overflow in July and stand empty in March. The number that matters is not what falls in the wettest month but how much you can still be holding in the driest.
Why the ridge runs short in the first place
Bandipur is a saddle on the Mahabharat range at about 1,030 m, with no watercourse at ridge level. Supply has to be lifted from sources below, and the monsoon that brings the rain is the same season that puts landslides through intake pipes and across the Dumre road. Stored rain is one of the few things on the ridge that does not depend on that road staying open.
First flush, in one sentence
Fit a simple diverter — a length of downpipe that fills and closes off before the clean water reaches the tank — so the dirtiest water from the start of each storm never gets in. It is the cheapest single thing that improves what comes out of the tap.
Where to get help
Bandipur Rural MunicipalityThe ward and municipality offices are the place to ask about supply schemes, tanks and any support programme. Office line 065-520123.