Home  Pilot Project Areas  Cuddalore, TN  Introduction
 
     
 
 
 
 
 
 
 
Lower Vellar, Cuddalore District, Tamil Nadu
 
Introduction
The Lower Vellar watershed in Cuddalore District, Tamil Nadu, is characterized by coastal Tertiary Sedimentary rocks overlain by Quaternary Alluvium.
The freshwater occurs in the Quaternary Alluvium and underlying Cuddalore Sandstones of Tertiary Age, which are being tapped up to the depth of 250 to 300 m. The quality of groundwater is in general potable, except for the coastal tract where saline groundwater occurs in the Quaternary Alluvium and freshwater aquifers are only in the underlying Cuddalore Sandstones. Cuddalore formation holds a lignite bed.
The aquifer system in the area to the depth of 250 to 300 m comprises four aquifers, two overlying the lignite bed, and the other two underlying it.
 
The key groundwater management issues are the following:
Sustainability of present groundwater abstraction, which requires water budgeting of each aquifer
Saline water intrusion into ground water system
Availability & sustainability of ground water resources of shallow and deeper aquifers
 
Addressing these issues require ascertaining the geometry of each aquifer, their piezometric heads and parameters, recharge characteristics, and groundwater abstractions.
The methodology developed for mapping aquifers in the area can be replicated in coastal tracts of Andhra Pradesh, Gujarat, Kerala, Orissa, Tamil Nadu, and West Bengal.
 
AQUIFER MAPPING PROJECT IN TAMIL NADU AT A GLANCE
  Assessment Unit Watershed / Taluk / Block  
  Area 344 sq.km / 344000 ha  
  District Cuddalore  
 
Figure 6.1: Google earth map of study area.
 
  Normal Annual Rainfall 1400 mm  
  River Basin Lower Vellar sub-basin  
  Major rivers / streams Paravanar and Uppanar rivers  
  Geology Alluvium underlain by Tertiary sandstones  
  Hydrogeology There are four aquifers: two above the lignite bed and two below the lignite bed. These aquifers are separated from each other by clay layers.  
  Aquifers The aquifers are in alluvium and in Cuddalore sandstones. They have good potentiality.  
Figure 6.2: Schematic views of the aquifer systems in the area.
 
  Depth to water table (Min. / Max.) Pre-monsoon :
- 10 to 20 m bgl for the unconfined aquifers (2011).
- 20 to 60 m bgl for deeper aquifers (2011) (m bgl : m below ground level)
 
  Stage of ground water development 71%  
  Groundwater quality Potable except for the coastal part where it is saline.
  EC Chloride
Shallow aquifers    
Deep aquifers    
 
  Major issues
Sustainability of present groundwater abstraction
Saline water intrusion into ground water system
Availability & sustainability of ground water resources of shallow and deeper aquifers
 
  Methodology of study Study of individual aquifer through a combination of geophysical methods & drilling and analysis of hydrogeological, hydrochemical & collateral data for estimating and managing the ground water resources.  
  Expected outcomes of aquifer mapping Maps of aquifers and their potentiality and quality, aquifer-based management  
  Geographical applicability of the methodology Coastal tracts of Andhra Pradesh, Gujarat, Kerala, Orissa, Tamil Nadu, and West Bengal