See how much rain your roof could catch — in a normal year and in the last 30 days — how many days of household water that is, and how many summer tanker loads it saves.
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Mazraat El Mechref has always lived on stored rain. The old survey of the hill noted olives, figs and cisterns; the farming is rain-fed (ba'l), and in the long dry summer households buy water by the tanker. This planner shows how much rain your own roof could catch in a normal year — and how much has actually fallen in the last month — how many days of household water that is, and how many tanker loads it stands in for. Type your roof size and how many people live there.
In a typical year, this roof could catch about
48,000 litres of water
from about 600 mm of rain a year
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.
Only about 0 mm of rain has fallen in the last 30 days. Outside the rainy season there is little to catch — the typical year above is what a full season brings.
These are estimates, not a promise
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
Rainfall varies a lot around here
Assumes a hard concrete roof feeding a cistern through gutters — the usual roof here. About a fifth of the rain that lands is lost to the first wash-off, splashing and overflow, so four-fifths is counted.
Counted at 25 litres per person a day — enough for drinking, cooking and basic washing. A normal Lebanese household with a full mains supply uses far more (well over 100 litres a person), so read the 'days of water' figure as basic needs, the way it matters when supply is short.
The winter rains fall between about November and March; June, July and August bring almost none. A roof that fills a cistern over the wet months is water you don't have to buy when the dry summer comes.
In summer many households buy water by the tanker — a common load is about 2,000 litres, often more than once a week. Every load you don't have to buy is money kept, so a full cistern from the winter is worth counting.
The dirtiest water is the first few minutes of a storm, when the roof rinses. A simple first-flush diverter — a length of pipe that fills and sets that first water aside before the rest runs to the cistern — keeps the stored water cleaner.