Rainwater harvesting structures along the stormwater drains will enable the use of rainwater endowment along with preventing floods
Representative photo:iStock. Chandigarh, one of India’s leading smart cities, hits the headlines whenever torrential rain occurs. Newspapers usually carry elaborate reports on citizens fighting the water logging in their streets. A mix of natural and artificial causes is to be blamed for such urban floods that disrupt day-to-day activities.
However, proper interventions can address issues related to urban floods.
The city’s geographic location is one reason why it gets inundated during incessant rains. Chandigarh is located on a double-layer aquifer — a shallow and deep aquifer system.
Water levels in the deeper aquifer range from 15-70 metres below ground level, and that in the shallower aquifer is 1.22-45 metres below ground level (in the pre-monsoon period), according to data on groundwater.
The city sources its water from the deeper confined aquifer, said sources from the Central Groundwater Board (CGWB). These aquifers do not get recharged naturally and need intensive plans to restore recharge bores.
CGWB report noted a hydraulic difference between the northern and southwestern parts of the city. As a result, there is a flow of water from the north to the south, resulting in the natural recharge of groundwater in the southwestern sectors.
Groundwater levels in these sectors are already shallow; flooding due to natural recharge impact the region even after a small spell of rain.
The water from this part of the city ultimately feeds the shallow aquifers of the southern sectors.
There is no concrete plan for using these shallow aquifers for drinking water purposes as there is a fear of bacteriological contamination due to open defecation in the rural areas and informal settlement in the northern part of the city.
A 2016 report by Delhi-based think tank Centre for Science and Environment (CSE) found that the city hasn’t formulated any plans for its shallow aquifers. Even CGWB reports pointed out the rising groundwater levels in these aquifers.
CSE research also noted other reasons for flooding in the city. The stormwater drains were initially planned to drain the water from the northeast to the southwest of the city. It was easier to plan this drainage system as it aligns with the slope of the city. However, the drains were designed considering a peak intensity of half an inch of rainfall per hour.
Over the years, the open and green spaces in the city were concretised, increasing the runoff coefficient. Thus, flooding of stormwater drains becomes a common phenomenon every year.
Although Chandigarh’s administration has enhanced the capacity of stormwater drains, enough has not yet been done. CSE’s research found that rainwater harvesting structures along the stormwater drains will enable the use of rainwater endowment along with preventing floods. The harvested water can be used to recharge the groundwater sources that the city relies on.
The authority needs to plan the usage of shallow aquifers to prevent waterlogging. At the same time, the city needs to recharge the deeper aquifers with rainwater. Chandigarh is facing the ire of a rising groundwater table on the one hand and a declining water level on the other. It is time for the city to think of a water plan to recharge its aquifer and solve the water logging issues.
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