Rainwater Harvesting in Urban India
Rainwater harvesting is a basic system that can be possible with low innovation, low to moderate costs and is applicable even at a small-scale with a minimum of specific knowledge. The collected water can supplement general water sources when they turn out to be scarce or are of low quality. Additionally, it is a decent substitute in times of dry season or when the underground water level drops. This innovation is versatile to a more extensive assortment of conditions from wealthiest to the poorest societies, as well as from the wettest to the driest region.
The fundamental idea: The example chart of rainwater harvesting incorporates the accompanying steps.
Catchment area: This is the place from where the rainwater is collected. These can be different locations and in various sizes.
Conveyance: The drainage system required to transfer the rainwater from the catchment to the storage location, usually the pipeline. The basic filtration, and separation of debris and other material from the water is done.
Storage: The place where the water is stored for future use. It can be underground or on surface.
Delivery: The place or the system from where the collected rainwater is extracted for use.
Now let us understand every step in detail for better understanding.
Catchment area: The rainwater can be collected from the below locations.
1.Rooftops: Buildings with water-resistant roofs can be the best catchment areas accessible free of cost.
2.Paved and unpaved areas: In areas of low rainfall, the larger areas like landscapes, open fields, gardens, streets and roadways and other open places can be effectively used to collect the rainwater.
3.Local Waterbodies: Tanks, ponds or lakes can be the best source to collect rainwater to meet the requirements of the urban areas and revive the groundwater tables.
4.Stormwater Drains: Stormwater drains in societies, if maintained well, can be the basic and cost effective means for collecting rainwater.
Gutters: These are the channels around the edge of a slanting rooftops to collect and transport rainwater to the storage tank. These gutters can be made using galvanized iron sheets, PVC material, bamboo or betel trunks.
Storage: The rainwater thus collected can be stored in the places mentioned below.
Energizing of dugwells and abandoned tubewells: In alluvial and hard shake zones, there are a large number of wells which have either gone dry or whose water levels have declined drastically impressively. These can be revived specifically with rooftop run off.
Settlement tanks are used to remove sediment and other coasting polluting influences from water. A settlement tank is similar to an ordinary storage container having provisions for inflow, outpouring and flood. A settlement tank can have an unleveled base surface to permit standing water to permeate into the soil. Any container, with sufficient limit of capacity can be utilized as a settlement tank.
In this case, the rooftop runoff is not directly led into the service tubewells, to dodge possibilities of pollution of groundwater. Rather, water is gathered in the revive well, which is a temporary storage tank situated close to the service tubewell, with a borehole, which is shallower than the water table. This borehole must be given a casing pipe to prevent the collapsing of soil. A channel chamber including sand, rock and stones is given to capture the polluting influences.
A recharge pit is usually dug 1.5m to 3m wide and 2m to 3m deep. This boundary wall of the excavated pit is lined with a brick/stone wall with small openings at similar distances. The top area of the pit can be secured with a punctured cover.
Percolation pits, one of the simplest and most effective means of harvesting rainwater. Designed on the basis of expected runoff, they are loaded with rocks or block jam and stream sand, secured with punctured solid pieces wherever essential.
A recharge trench is a persistent trench excavated in the ground and refilled with permeable media like stones, rocks or broken blocks. The length of the energize trench is chosen according to the measure of overflow anticipated. The revive trench ought to be intermittently cleaned of accumulated debris to maintain the intake capacity.
The recharge troughs are set at the entrance of a residential/institutional complex. These structures are like revive trenches except that the excavated part is not loaded with channel materials. Keeping in mind the end goal to encourage rapid energize, boreholes are drilled at regular intervals in this trenc.
Altered infusion well:
In this strategy, water is not pumped into the aquifer but rather permitted to permeate through a channel bed, which includes sand and rock. An adjusted infusion well is generally a borehole, which is drilled to the desired depth depending upon the geological conditions. The annular space between the borehole and the channel is loaded with rock and compressor till it gives clear water. To prevent the suspended solids from entering the revive tubewell, a channel instrument is given at the top.