Water as Leverage- Setting the scene for a call for action

Water as Leverage for Resilient Cities Asia Setting the Scene for a Call for Action Content
1.2.1
Historical Drainage System
Chennai’s hundreds of connected ponds, temple
tanks, extensive wetlands and lakes were
historically used as water basins for irrigation and
still serve as flood accommodators. This ingenious
system captured rainwater and protected the city
from flash floods. After the water bodies lost their
function for irrigation, people failed to recognize the
other services this system delivered to the city. The
rivers still function relatively well as drains, but the
encroachment of ponds, wetlands and canals has
reduced their drainage capacity to a minimum, while
solid waste and illegal constructions cause many of
the canals and rivers to clog. This is one of the main
issues related to the major floods that occur every
few years. In addition, siltation of the river mouths
blocks the water flow towards the sea, basically
making the rivers stagnant.
the tap water chain. However, most buildings
in Chennai individually pump consumption
water from great depths under the city, hence
affecting the underground and its natural water
system. By shortcutting the system the natural
water balance in the underground is distorted:
too little rainwater infiltrates to recharge the
superficial and deep aquifers under the city.
The railway station in the Buckingham Canal.
Canal used for navigation
Encroachment by
illegal housing
Landfil
Pollution
and solid waste
Rainwater storage pond
Agriculture
irrigated by ponds
Bridge
past
present
The Buckingham Canal
has been encroached
by infrastructure, landfill
and housing.
Chennai has its roots at the mouth of Cooum
River and is situated on a coastal plain
that stretches from the southeast of India
to Bangladesh. Three rivers cross the city:
Cooum River in the middle, Adyar River in
the south and Kosasthalaiyar River that flows
through the northern industrial fringes of the
city. However, these rivers are small and mostly
stagnant, carrying too little fresh water to serve
as water supply for the city. For this reason,
Chennai has always been dependent on
rainwater. With the city built on a slight slope,
city inhabitants constructed the ingenious
Ery system, consisting of interconnected
basins, wetlands and canals. Together with
a network of reservoirs and local harvesting
mechanisms, such as water temples, the
Ery system was responsible for the storage
of as much rainwater as possible during the
monsoon season, the restoration of shallow
aquifers and the provision of freshwater for
the rest of the year. Besides the ingenious
Ery system, Chennai has another astounding
man-made water work: the Buckingham Canal.
This canal was constructed during the British
colonial period for cargo transport. It is over
700 kilometers long and connects the three
rivers. Even though it has lost its function for
water-based transport, it still has an important
function in discharging rainwater.
Chennai’s gentle slope crosses different
types of water bodies: the water basins
upstream, the rivers and canals between
these basins and large wetland areas parallel
to the coast. The city’s water system is a
collection of separate, but interconnected,
functioning complexes that consist of varying
compositions of water bodies. Within this
complex system, the buildings within the urban
fabric play an interesting role. On the one hand,
buildings can normally play a modest positive
role in catching and infiltrating rainwater,
while on the other they are also at the end of
Encroachments by real estate developments. The small islands are
attempts to create mirco biotopes in this pond.
Activities by the waterfronts are common,
whether by the rivers, wetlands or by the beach.
Connection ditch
disappeared
Overflow ditch
Solid waste
Encroachment
Pond removed for
urban development
Fishing, bathing, cooking
High turnover of inhabitants
= low social connectivity
The Erie system is a
way to store surplus
water during the monsoon
season. Much of
it has disappeared and
existing ponds are in a
bad shape.
154 CHENNAI
Water Issues
PART 2/Background Information on the Partner Cities
155