Why storage matters more than access to rain itself

Nairobi does receive meaningful rainfall across the year, but nearly all of it falls within two relatively short seasons. The real constraint most members face is not a lack of rain overall, but a lack of a way to hold on to it through the long dry stretches between seasons.

Basic catchment setups

The simplest catchment system channels roof runoff through a gutter into a storage container — anything from a repurposed drum to a proper storage tank, depending on what a household can afford. Even a modest 200-litre drum, filled repeatedly across a rainy season, provides a meaningful buffer for a small kitchen garden through the following dry weeks.

For households without a permanent roof gutter, we teach a simple ground-level catchment using a shallow, lined pit positioned to collect runoff from a sloped surface, though this method loses more water to evaporation and seepage than roof catchment and is treated as a secondary option.

Keeping stored water usable

Stored water needs a secure, mosquito-proof cover, both for basic health reasons and to prevent evaporation loss. We advise members to keep storage containers off direct ground contact where possible, using a simple raised platform, which reduces contamination and makes drawing water out easier.

Planning storage capacity around actual need

Rather than storing as much water as physically possible, we help members estimate what their garden actually needs to bridge a typical dry spell, based on bed or sack size, and size their storage system to that real need. Oversized storage that a household cannot actually fill from a single roof's runoff is wasted investment; undersized storage runs dry before the rains return. Matching the two is the actual skill being taught here.

Basic maintenance to keep a system working

A catchment and storage system is not maintenance-free once built. Gutters need periodic clearing of leaves and debris, particularly ahead of the rainy season, since a blocked gutter can send runoff away from the storage container entirely rather than into it. Storage containers benefit from an occasional check for cracks or damage, particularly for repurposed drums that may have been used for other purposes before being adapted for water storage, since some previous contents can leave residue that affects water quality.

We encourage members to build a simple seasonal checklist — clear the gutters, inspect the storage container, check that the cover is still secure — to run through just before the rains begin each year, since a system neglected between seasons can lose much of its effectiveness exactly when it is needed most.

Sizing a system for a growing household need

A rainwater storage system built for a single sack garden's needs may prove undersized within a year or two if a household expands to several sacks or a larger bed, which is why we advise members to build in some capacity beyond their current immediate need when constructing a new storage system, where budget allows. Expanding an undersized system later is generally more expensive and disruptive than building modest extra capacity from the start.

We help members think through this kind of forward planning during training, since a storage system is one of the more significant upfront investments a household makes, and getting the sizing reasonably right the first time avoids a costly and avoidable rebuild.

The best time to think seriously about storage capacity is well before the rains actually arrive, since building or acquiring a tank, drum, or gutter system takes some lead time, and members who wait until the rains have already started often miss capturing the first, often heaviest, weeks of runoff. We raise this topic with members every year specifically ahead of the rainy season for that reason. We also encourage members to think of rainwater storage as an investment that pays for itself gradually through reduced water purchase costs over several seasons, rather than expecting the full value to show up immediately in a single dry stretch. Members who have used a storage system across multiple dry seasons consistently describe the cumulative saved cost as more significant than they initially expected when first building the system.

Key takeaways

  • The real constraint is usually storage, not a lack of rainfall across the year.
  • Roof gutter catchment into a drum or tank is the simplest reliable setup.
  • Stored water needs a secure, mosquito-proof cover to stay usable and safe.
  • Size storage capacity to actual garden need, not to whatever container is available.

Frequently asked questions

How much water storage does a small kitchen garden need?
It depends on bed or sack size and typical dry-spell length — we help members estimate this rather than guessing, since oversized storage wastes investment and undersized storage runs dry too early.

Is ground-level catchment as good as roof gutter catchment?
No — ground-level catchment loses more water to evaporation and seepage, so we treat it as a secondary option when roof gutters aren't available.

Can stored rainwater be used for drinking?
We advise against it without proper filtration and treatment — our guidance covers garden use only, not household drinking water.