The warning signs are all there: Lahore`s infrastructure was tested to the limits, and in some cases even collapsed, as heavy rainfall lashed the provincial capital of Punjab in the last week of June. Much of the rainwater was wasted as drainage systems in Lahore or, for that matter, other cities in the country seem virtually non-existent. No water could be stored for use, neither for home use nor for use for public services. Are we, as a nation, complicit in criminally wasting water when there isn`t even enough for consumption? According to a report by the United Nations Development Programme (UNDP), in another seven years, Pakistan is likely to run dry. Considering that water demand is constantly on the rise owing to population increase, there is constant degradation of water quality, rise in cost of supply and maintenance infrastructure, and minimal groundwater recharging with depletion of water levels.

There is little doubt that the issue of water scarcity needs to be dealt with on war footing and one method to do so is to harvest rainwater. In fact, rainwater harvesting (RWH) is now an established technique of collecting and storing rainwater into natural reservoirs or tanks. And one of the most common ways to do so is rooftop harvesting a method that relies on citizens to be proactive and not rely on the government for help.

In essence, whenever there are rains, the flow of rainwater is intercepted and directed to a storage area.

Studies show that 30 to 45 percent of water usage in urban areas is for washing, gardening, vehicle washing, and in affluent areas up to 20 percent is used for flushing WCs, and this usage can easily be met through RWH.

Stored rainwater could be used to plant trees and for soil regeneration, among other things.

All that needs to be done is to connect the drainage pipe from the roof to a drum below if the pipe drains out into a cemented portion of the house where the water can collect. The drum, in turn, should have a pipe connected to it that drains the collected water into an aquifer pit dug in the garden or, if there is no garden, then into a tank made for the purpose in a concrete portion of the house, or directly into a pit, if it drains into the garden.

According to architect and conservationist Yasmeen Lari, aquifer pits that are one to two metres wide and two to three metres deep are sufficient to meet storage requirements of houses with a 100-square-metre roof.

To store potable water, the base should have a layer of boulders five to 20 centimetres in size, with five to 10 millimetres of gravel and 1.52mm graded coarse sand on top. This will allow filtration of rainwater.

For smaller roofs, the pits could be filled with brick bats.

A fine mesh should be placed on top to avoid leaves, insects, sand and other impurities from falling in.

If the tank is being used to store water for domestic consumption, a tap could be installed, and the water could be used directly to water the garden or for washing cars. For other domestic use, such as for flush systems, a separate pipe would have to be installed. In cases where houses, or even buildings, are still under construction, it is imperative that these tanks be built as part of the floor plan, as they are the need of the hour.

Even with low rainfall, RWH can lead to saving substantial quantities of water that can be used for drinking as well as for non-potable use such as domestic, indoor plantation and agriculture as well as for aquifer replenishment.

Storing rainwater serves a dual purpose, as mentioned earlier, as it also helps prevent flash floods. Usually in Pakistan, runoff from roofs adds to the runoffs from pavements and hard surfaces. This means that streets and lanes get inundated as do storm water nullahs (many of which tend to be blocked with debris or trash). Even if they could be cleared, they would hardly be able to carry the enormous quantity of water flowing from roofs, pavements and other hard surfaces.

This means that the runoff from pavements must be harvested as well. In order to avoid flooding, street water must not be allowed to enter the drainage system. Instead, catchment areas should be created so that water is trapped in collection devices, such as storage tanks, deep V~shaped trenches, disused pits and tube wells.

Perhaps the notion of rainwater harvesting is uncharted territory in Pakistan. But, in many countries, it is mandatory to collect rainwater, especially in all new developments.

Take Central American countries, for example, where by law storage tanks have to be provided in all constructions to store a minimum of 400 litres of rainwater per square metre of roof area. Perhaps this is also the future for Pakistan,where the destruction caused by flash floods affects stability of structures and grinds life to a halt.The writer is a freelance journalist She tweets @ShanazRamzi