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• Thiruvallur district is the northern most coastal district of Tamil Nadu.
• The district is bounded by the Bay of Bengal in the East, Vellore district of Tamil Nadu and Chittoor district of Andhra Pradesh on the West, Nellore district of Andhra Pradesh on the North and on the South by Kancheepuram district.
• It lies between 12º 55'N to 13º 34'N Latitude, 79º 17'E to 80º 21'E Longitude and has an areal extent of 3550 sq.km.
• There are 14 Blocks, 526 Villages and 3842 Habitations in the District.
 Physiography and Drainage:
• Thiruvallur district varies from featureless pediplain to residual and structural hills.
• The Thiruthani and R.K.Pet hills form part of the important landmarks. The Coastal tract is marked by beach ridges with a general slope towards the east.
• The Araniar, Kortaliyar, Adayar and Coovum are important rivers draining the district.
• The Araniar originating in Andra Pradesh flows between Ponneri and Thiruvallur taluks and joins the Bay of Bengal near Pulicat
• The Coovum has its origin in the Surplus water from the Coovum tank in Sriperumbudur taluk and feeds the Chembarampakkam tank through a Channel.
• The Poondi reservoir and Red hills are important tanks. The Pulicat tank is considered to be an important lagoon.
The average annual rainfall and the 5 years rainfall collected from IMD, Chennai is as follows:
Acutal Rainfall in mmNormal Rainfall in mm
Rock TypeGeological Formation
Sedimentary Rock 80%
Hard Rock 20%
Charnockite, Gneiss, Conglomerate,
Sandstone, Shale, Laterite,
Alluvium and Marine deposits
Type of Aquifer Water table conditions in Hard Rock Areas.
Aquifer parametersHard rockAlluvial formation
Well yield in lpm45 – 220 150 – 400
Transmissivity (T)m2/day 10 – 80200 – 300
Permeability (K)(m/day))0.5 – 2.520 - 30
Depth of Water level5m to 12.5m
 Ground Water Level::
The Ground Water levels from the 35 number of observation wells of TWAD have been analysed for Post-Monsoon and Pre-Monsoon. Since 1991 average Ground water level in m Below Ground Level for pre and post monsoon is as follows:
With a view to enhance the Sustainability of the drinking water sources, recharge structures are being implemented by TWAD Board under various State and Central Government assistances.
The Recharge Structures implemented so far is as under.
Recharge Structures
Check Dam Percolation Pond Recharge Pit Recharge Trench Others Ooranies Defunct Bore well Recharge Recharge Shaft Roof top RWH Hydro Fracturing Total
369 13 15 41 438
 Groundwater Potential as on March 2011 (as per CGWB):
Net Groundwater Availability (in MCM)728.40
Existing Gross Groundwater draft for all users (in MCM)492.89
Stage of Groundwater development (in %)68%
Categorization of DistrictSafe
 Categorization of Firkas:
The status of Categorization of firkas as of March 2011 for the District is shown below.
Categorisation based on Extraction (as on 2011) No. of Firkas Firkas
Over Exploited (>100%) 4 Ambattur, Cherukkanoor, R.K.Pet, Vengathur
Critical (90%-100%) 8 Uthukkottai, Balapuram,Erumbi, Kadambathur,
Mappedu, Gummidipoondi, kannigaipair,Thirunindravur.
Semi Critical (70%-90%) 14 Kanagammachattram, Kattur,
Madhavaram, Periyapalayam,
Poonamallee, Poonimangadu, Pothattur
Redhills, Thirumazhisai, Tiruttani,Ammanbakkam, Avadi, Pallipattu, Morai, Velakapuram.
Safe (<70%) 19 Elavur, Gnayiru, Kolur,
Madhapakkam, Maduravoil, Manavor, Pothatturpettai
Pandur, Pennalurpett, Ponneri,
Poondi, Poovalambedu, Sholavaram, Arani
Thirupalaivanam, Thiruvalangadu,
Thiruvallur, Tirur, Velliyur.
Others (Poor& Saline) 1 Minjur
Total 46
Water supply status as on 1.4.2017
 Rural Habitations
Total No. of Rural Habitations: 3842
Partially covered 0 (10-39 lpcd )
Fully covered 3842 (40 lpcd and above)
 Urban Towns (Water supply status - Sep 2016)
S.NOName of Towns Population Present water supply level LPCD
1 Thiruvallur 56074 72
2 Avadi 345996 48
3 Poonthamallee 60607 82
4 Thiruthani 44728 71
5 Thiruverkadu 62824 70
Town Panchayats
1 Naravarikuppam 20946 82
2 Thirunindravur 37095 78
3 Thirumazhisai 19733 110
4 Gummudipoondi 18891 127
5 Pallipattu 8721 149
6 Arani 12833 109
7 Ponneri 31025 126
8 Pothatturpettai 22040 116
9 Uthukottai 12740 80
10 Minjur 28337 86
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