Water Scarcity in Indian Cities: Why Rainwater Harvesting Matters More Than Ever

In the summer of 2019, Chennai made international news for the wrong reason. The four main lakes that supply the city had nearly dried up. Lorries carrying water became a common sight, many offices asked employees to work from home, and families planned their day around the arrival of the tanker.

The strange part? Chennai is not a dry city. It gets a good amount of rain in a normal year. The problem is that most of that rain runs off into drains and the sea instead of being saved. That is where rainwater harvesting comes in.

💧 Why Indian Cities Run Short of Water

• Concrete everywhere: roads, buildings and paved yards don’t let rain soak into the ground.
• Lost lakes: many lakes and ponds have shrunk, been encroached or filled with silt over the years.
• Over-pumping groundwater: borewells keep going deeper as the water table falls.
• Uneven rain: a weak monsoon year, as with some El Niño years, can quickly turn a shortage into a crisis.
• Growing population: more people in cities means more demand — a challenge I touched on in India’s population: challenge and opportunity.

🏛️ Tamil Nadu Led the Way

After a severe drought in the early 2000s, Tamil Nadu became a pioneer. In 2003, the state made rainwater harvesting (RWH) structures mandatory for all buildings through an ordinance that amended its municipal laws. Building owners were given a deadline to install them, and new buildings need RWH to get approvals.

The results were encouraging at first — many areas saw groundwater levels improve after good rains. But over the years, many structures were neglected: pits got clogged, pipes broke, and some systems were built only on paper. The 2019 crisis was a wake-up call that having a structure is not enough; it must work.

The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) offers guidance on RWH designs on its website, cmwssb.tn.gov.in.

🔧 How Rainwater Harvesting Works

The idea is simple: catch the rain where it falls. There are two main ways:

1. Store it

Rain from the roof is collected through pipes, passed through a simple filter (sand, gravel, charcoal or a mesh filter), and stored in a sump or tank. This water can be used for washing, gardening and flushing — and with proper treatment, even more.

2. Recharge the ground

Roof and surface water is directed into a recharge pit, percolation well or an old/defunct borewell. The water slowly seeps down and refills the groundwater, which your borewell and your neighbours’ wells depend on.

How much water can a roof collect? A rough rule: every 1 mm of rain on 1 square metre of roof gives about 1 litre. So a 100 square metre roof receiving 1,000 mm of rain in a year can catch up to around 1 lakh litres — minus some losses. That is a lot of water to let go down the drain!

“Every roof is a small catchment. Every home can be a small reservoir.”

✅ Check Your RWH Before the Rains

Most homes in Tamil Nadu already have some RWH structure. The question is whether it works. Before the monsoon:

1. Clean the roof — remove leaves, dust and debris.
2. Check the pipes — make sure downpipes are connected to the pit or sump, not to the street drain.
3. Clean the filter — replace the sand or wash the mesh.
4. Desilt the pit — remove the top layer of silt so water can seep in.
5. Look after open ground — keep some unpaved soil around the house so rain can soak in.

In apartments, raise it in the association meeting and plan a yearly maintenance check. It costs little and benefits everyone.

🚿 Save Water Every Day

• Fix dripping taps and leaking tanks quickly — a slow drip can waste many litres a day.
• Reuse RO reject water for mopping, washing vehicles or plants.
• Use a bucket instead of a running hose to wash cars and bikes.
• Water plants in the early morning or evening to reduce evaporation.
• Turn off the tap while brushing and soaping.

✨ Takeaway

Water scarcity in our cities is not only about less rain — it is about wasting the rain we get. Tamil Nadu’s 2003 rule showed what is possible. Now it is up to each of us to keep those systems working. Clean your pit, catch the rain, and save every drop. Future summers will thank you.