Monitoring of ground water quality is an effort to obtain information on chemical quality through representative sampling in different hydrogeological units. The chemical quality is being monitored by Central Ground Water Board once in a year through observation wells located all over the country, in regular monitoring programme. Apart from these observation wells the quality is also monitored through various studies like ground water management studies, ground water exploration etc. The ground water monitoring activity is aimed at generating background data of different chemicals constituents in Ground water on a regional scale.
Ground Water Quality Scenario in India
Indian Sub- Continent is endowed with diverse geological formations from oldest Achaeans to Recent alluviums and characterized by varying climatic conditions in different parts of the country. The natural chemical content of ground water is influenced by depth of the soils and sub-surface geological formations through which ground water remains in contact. In general, greater part of the country, ground water is of good quality and suitable for drinking, agricultural or industrial purposes. Ground water in shallow aquifers is generally suitable for use for different purposes and is mainly of Calcium Bicarbonate and Mixed type. However, other types of water are also available including Sodium-Chloride water. The quality in deeper aquifers also varies from place to place and is generally found suitable for common uses. There is salinity problem in the coastal tracts.
Ground water in major parts of the country is potable. However some water quality issues are reported from isolated pockets from various parts of the country. Higher level of the constituents like Arsenic , Fluoride, Iron ,Salinity in ground water are due to the natural geological phenomena. These are the geogenic contaminants found in ground water. Manmade activities like mining activity, disposal of industrial wastes and untreated domestic wastes are responsible for contamination like nitrate and heavy metal.
Fluoride in ground water
As per BIS, the maximum permissible limit for F in drinking water is 1.5 mg/l.Main source of fluoride in groundwater is considered to be fluoride-bearing minerals such as fluorspar (CaF2), fluorapatite [Ca5(PO4)3F], cryolite, and hydroxylapatite in rocks. Some anthropogenic activities such as use of fertilizers, pesticides and sewage and sludge etc. for agriculture have also been indicated to cause an increase in fluoride concentration in ground water.
Fluoride if consumed in excess of 1.5 mg/L over long periods of time produces severe effects on human health, such as dental and skeletal fluorosis (crippling bond), osteoporosis, hip fracture, arthritis, mental retardation etc .Fluoride above permissible limit in ground water has been reported from parts of 20 States (Andhra Pradesh, Assam, Bihar, Chhattisgarh, Delhi, Gujarat, Haryana, Jharkhand, Jammu & Kashmir, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Orissa, Punjab, Rajasthan, Tamil Nadu, Telangana, Uttar Pradesh and West Bengal.
Arsenic in ground water
As per the recommendations of the Bureau of Indian Standards (IS:10500,2012), the permissible limit of Arsenic in drinking water is 0.01mg/l with no relaxation.
Chronic exposure to drinking water having arsenic contamination beyond permissible limit may cause several skin problems including arsenicoses characterised by dark spots on body and limbs, thickening of palms and soles etc, Bowen’s disease ,non healing ulcers etc.
Elevated levels (>0.05 mg/l) of Arsenic in ground water was reported from parts of 10 States of West Bengal, Assam, Bihar, Jharkhand, Uttar Pradesh, Punjab, Haryana, Chhattisgarh, Karnataka & Manipur .
A recent survey by CGWB has has shown Arsenic concentration in excess of 0.01 mg/l from patches from additional 11 States. In these areas arsenic occurrence is reported from only limited samples and resampling is envisaged.
Salinity in ground water
Salinity is the saltiness or dissolved salt contents of a water body. It is mostly influenced by aquifer material, solubility of minerals, duration of contact and factors such as permeability of soil, drainage facilities, quantity of rainfall and above all, the climate of the area. The salinity of ground water in coastal areas may be due to air borne salts originating from air water interface over the sea and also due to over pumping of fresh water which overlays saline water in coastal aquifer systems.
Problem of salinity (EC>3000 micro siemens/cm) has been observed in 15 states (Andhra Pradesh, Delhi, Gujarat, Haryana, Karnataka, Kerala, Madhya Pradesh, Maharsahtra, Odisha, Punjab, Rajasthan, Tamil Nadu, Telangana, Uttar Pradesh, West Bengal.)
High concentration i.e. (above BIS norm of 45 mg/l) of nitrate in ground water has been observed in 21 states of Andhra Pradesh, Telangana , Bihar, Chhattisgarh, Delhi, Gujarat, Haryana, Himachal Pradesh, J&K, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Orissa, Punjab, Rajasthan, Tamil Nadu, U.P, Uttarakhand, West Bengal.
Iron in ground water
High concentration of Iron above the BIS permissible limit of 1mg/l in ground water has been observed in the states of Andhra Pradesh, Assam, Arunachal Pradesh, Bihar, Chhattisgarh, Goa, Gujarat, Haryana, Jharkhand, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Manipur, Meghalaya, Nagaland, Odisha, Punjab, Rajasthan, Tamil Nadu, Telangana, Tripura, U.P, West Bengal & Andaman & Nicobar.