Chennai has run out of water. Consecutively weak monsoons failed to replenish parched reservoirs, pushing the city to a severe water crisis well ahead of summer this year. As the coastal city veers between floods and droughts with increasing frequency, the debate on its causes has focused on how uncontrolled urbanisation and poor planning has caused its current crisis.

The stunning rate and spatial concentration of its growth is best illustrated by these maps that chart the city’s expansion since 1997. They were put together as part of the Indian Institute for Human Settlement’s India Urban Atlas publication, which visualises the expansion of 100 Indian cities over the past two decades using publicly available data.

The images below show the built-up land cover in the region for 1997, 2009 and 2016, overlaid on a relief map, which represents the region’s physical terrain. Blending the two explains how urbanisation has encroached upon the city’s water bodies and disrupted its drainage networks.

The Chennai Metropolitan Area, one of the largest urban agglomerations in the country, encompasses 1,189 sq km. The Chennai Corporation administers 426 sq km of that area. The region is mainly fed by three rivers and four reservoirs, and is home to natural wetlands such as the Pallikarnai Marsh in the south of the city. The city’s hydrology is also vitally supplemented by the Aquifer Recharge Zone, which restores groundwater levels through rainfall.

Both these areas have been marked on the map below and their boundaries drawn based on the Second Master Plan for Chennai Metropolitan Area – 2026 document. Both of them flank Chennai’s “IT corridor” (in yellow) or Rajiv Gandhi Salai, also known as Old Mahabalipuram Road or the OMR.

This ambitious development project was officially launched in 2008 and saw droves of real estate developers and IT companies flock to the region to profit from what was envisioned to be the city’s new centre of business. The uncontrolled growth (as evident in the difference between the maps for 2009 and 2017) led to extensive encroachment and polluting of the marshland and other water bodies in the region.

This expansion was concentrated on these networks, as the city did not have space to expand towards the north, where it shares a border with Andhra Pradesh. Additionally, with tourism development along the scenic East Coast Road that connects Chennai with Mahabalipuram and runs over the Aquifer Recharge Zone, this region has seen a significant increase in built-up area, lowering the quality of groundwater.

The location of the IT corridor – right between these valuable ecological areas – has pushed the city to the brink by raising the risk of flooding and drought. Encroachment and construction in these critical zones of the Pallikarnai Marsh and the Aquifer Recharge Zone has led to groundwater depletion, contributing to water scarcity.

The risk of flooding in the event of heavy rainfall is also heightened with run-off quickly forming due to the lack of natural ground cover, and because natural drains have been sealed off by unplanned construction.

The woefully inadequate urban infrastructure of the city and the problems it gives rise to is exacerbated by climate change. While governments look for solutions like desalination plants to deal with drought, this may not suit every city. Presently, most of Chennai is at the mercy of private water tankers to deal with the water scarcity, and it is important to realise that transporting water from far off regions and relying on water tankers is highly energy intensive, and leads to huge environmental impacts through high fuel consumption, rising emissions and traffic congestion.

If the city is to brace itself for future changes, it first needs to take immediate action to deal with current developmental deficits, because of which large numbers of the city’s urban poor continue to live in increasingly unsafe, deprived circumstances.