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Home , Cooum River, Kandaleru Dam, Kosasthalaiyar River, Poondi reservoir

BRAINSTORMING MEET ON WATER MANAGEMNET

Organised by REGIONAL METEOROLOGICAL DEPARTMENT & INDIAN METEOROLOGICAL SOCIETY, CHENNAI CHAPTER.

ECOSYSTEM BASED SOLUTIONS FOR DISASTER RISK REDUCTION IN CHENNAI CITY AND IT’S SUB URBS.

By T. Kanthimathinathan, Water Resources Management (Hydrology & Flood Control) Consultant, T.N.D.R.R.D.A. CHENNAI 03.08.2019. HYDROLOGICAL FEATURES OF CHENNAI AND ITS SUBURBS AN OVERVIEW NATURAL DRAINAGE SYSTEMS OF CHENNAI BASIN

 Chennai City and its suburbs in Thiruvallur and Kancheepuram Districts lies in Chennai Basin.  The main rivers flowing in Chennai basin are, 1. Araniyar 2. Kosasthalaiyar 3. Cooum 4. Adayar  There are only five outlets for discharging the entire runoff from Chennai Basin into are, 1. Creek (Araniyar River) 2. Creek () 3. mouth (Cooum River) 4. Adayar River mouth (Adayar River) 5. Kovalam Creek (Muttukadu & Pallikkaranai isolated water sheds) NATURAL DRAINAGE SYSTEMS OF CHENNAI BASIN Contnd….  The estuarine coastal fragile eco-systems available behind the above outlets of Chennai Basin are, 1. behind Pulicat creek 2. Ennore backwaters behind 3. Pallikkaranai marsh land and Muttukadu backwaters behind Kovalam Creek.  Chennai Basin is divided into the following eight sub-basins according to the drainage pattern 1. Sub basin 2. Araniyar Sub basin 3. Kosasthalaiyar Sub basin 4. Nagariyar Sub basin 5. Nandhiyar Sub basin 6. Cooum Sub basin 7. Adayar Sub basin & 8. Kovalam Sub basin

INTER BASIN TRANSFER SYSTEMS AVAILABLE FOR SUPPLEMENTING CHENNAI BASIN WATER NEEDS.

Krishna River to Chennai Basin : From Srisailam reservoir to Somasila reservoir through SRMC, link cannal, Velugodu balancing Reservoir, TGP main canal and CMP Canal.

From Somasila to through SKFF Canal, , SSG Canal (AP) and KP Canal (TN).

Palar to Kosasthalaiyar : From Palar Anicut near Walajah to Poondi reservoir across Kosasthalaiyar through – Govindavadi channel, Kaveripakkam tank surplus, Cooum River, Kesavaram Anicut, Kosasthalaiyar River, Poondi Reservoir

Palar to Adayar : From Palar Anicut near Walajah to (Near ) through Govindhavadi Channel-Kambakkal Channel, tank and its Surplus, Chembarambakkam tank and its Surplus. INTRA BASIN TRANSFER SYSTEMS AVAILABLE WITHIN CHENNAI BASIN FOR TRANSFER OF WATER FROM SURPLUS SUB BASIN TO DIFICIT SUB BASIN.

Araniyar to Kosasthalaiyar : From Araniyar Syphon across Araniyar river to Poondi reservoir across Kosasthalaiyar river through Kandaleru-Poondi Canal Anicut and in turn to Poondi reservoir.

Cooum to Adayar : From Zamin Anicut across Cooum River (between and ) to Adyar through New Bangaru channel, Chembarambakkam tank and it’s surplus course.

Kosasthalaiyar to Adayar : From Poondi Reservoir to Chembarambakkam through KWSP Link canal.

Kosasthalaiyar to Redhills Water Shed : (a) From Poondi Reservoir to Redhills Tank through KWSP Link Canal, KWSP feeder canal.

(b) From Thamaraipakkam Anicut to Redhills Tank through Upper supply channel, Tank and lower supply channel.

WATER POTENTIAL OF CHENNAI BASIN AT 75% DEPENDENTABILITY  Surface water potential - 1026 MCuM (36.233 TMC)

 Ground water potential - 1720 MCuM (60.742 TMC)

 Ground water extaction - 1460 MCuM (51.56 TMC)

Source : Micro level studies for Chennai Basin by Institute for Water Studies, PWD., during 2007.

FLOODS AND DROUGHTS FACED BY CHENNAI CITY

 Floods during the years 2005, 2008 and 2015.

 Droughts (Drinking water crises) during the years 2001, 2018 and 2019 SURFACE WATER STORAGRES AVAILABLE FOR CHENNAI WATER MANAGEMENT (WRD – MINOR IRRIGATION TANKS) Kancheepuram Thiruvallur District Total District Name of Sub S.No Basins No. OF Capacity No.of Capacity No.of Capcity No.of Capacity MCM Tank MCM Tanks MCM tank MCM Tanks

1 Gummidipoondi 0 0 40 12.48 0 0 40 12.48 2 Araniyar 0 0 199 97.82 0 0 199 97.82 3 Kosasthaliyar 1 1.06 176 207.3 0 0 177 208.36 4 Nagariyar 0 0 33 22.62 0 0 33 22.62 5 Nandhiyar 0 0 55 29.62 0 0 55 29.62 6 Cooum 0 0 61 49.13 21 8.69 82 57.82 7 Adayar 1 0.6 44 22.47 177 186.82 222 209.89 8 Kovalam 0 0 0 0 78 312.62 78 312.62 Total 2 1.66 608 441.44 276 508.13 886 951.23 230 157.92 Total 1116 1109.14MCM Or 39.169 TMC MAJOR CAUSES FOR WATER CRISIS IN CHENNAI AND ITS SUBURBS

 Increase in demand for water due to rapid expansion of IT Coriders, Industrial growth and urbanisation.

 Nature of flat terrain of city and lack of suitable storage space for holding surface run off during excess rainfall occurrence .

 Lack of suitable locations for creating new storage spaces due to the nature of flat terrain .

 The close proximity to the coastal area and its limitation in storing runoff from the urbanised catchments of coastal areas.

 Loss of natural coastal ecosystems to preserve fresh water aquifers and prevent sea water intrusion. POSSIBLE SOLUTIONS TO SOLVE THE WATER CRISIS

 Long term measures a)Increasing the capacity of the Natural waterbodies by deepening the entire water spread area of all the existing minor irrigation tanks up to its deeper sluice level by converting the shape of the tank from naturally formed cone to cylindrical shape to harness the run off during extreme weather events in the changing climate scenario. b)Re-establish the missing links of the drainage networks between the tank systems. c)Restoration of the Coastal and estuarine ecosystems to their pristine purity. POSSIBLE SOLUTIONS TO SOLVE THE WATER CRISIS - Contd…

 Short term measure a)Creation of roof top rain water harvesting structures to collect and store the rain water in the urbanised area which can meet - immediate domestic water needs. - reduce ground water extraction. - reduce the salinity of water due to recharge. UNDER GROUND RAIN WATER STORAGE SYSTEM (CONVENTIONAL METHOD) OPTIMAL CAPACITY FOR VARIOUS ROOF TOP AREAS (for a annual dependable rainfall of 60cm allowing 10% loses during initial period of downpour)

Optimal Capacity of Area of open ground Approximate cost of Size of UG storage S.No Roof Top Area the UG Storage required for storage Construction system System tanks (Convention Method)

17.5m X 10.0m = 15.30m X 7.70m X 1 5000 Sq.ft 2.50 Lakh Litres 175 Sqm (or) Rs.42.00 Lakhs 3.0m 1883 Sq.ft 22.5m X 13.5m = 20.25m X 11.35m X 2 10000 Sq.ft 5.00 Lakh Litres 304 Sqm (or) Rs.77.00 Lakhs 3.0m 3629 Sq.ft 33.0m X 13.5m = 30.5m X 11.35m X 3 15,000 Sq.ft 7.50 Lakh Litres 429 Sqm (or) Rs.119.00 Lakhs 3.0m 4616 Sq.ft 33.0m X 17.0m = 30.50m X 15.00m X 4 20,000 Sq.ft 10.00 Lakh Litres 561 Sqm (or) Rs.145.00 Lakhs 3.00m 6037 Sq.ft

Note: The estimated cost for construction of 6.0 Lakh Capacity underground storage tank (JICA Model) works out to Rs.1.50 Crores, since the cost initially forecasted as Rs.1.06 Crores is at 50% subsided rates for the materials imported from Japan THANK YOU