CPCB in collaboration with concerned SPCBs/PCCs established a nationwide network for water quality monitoring comprising 1013 stations in 26 States and 6 Union Territories. The monitoring is done on monthly or quarterly basis in surface waters and on half yearly basis in case of ground water. The monitoring network covers 200 Rivers, 57 Lakes, 5 Tanks, 3 Ponds, 3 Creeks, 12 Canals, 15 Drains and 320 Wells. Among the 1013 stations, 589 are on rivers, 61 on lakes, 15 on drains, 12 on canals, 6 on tanks, 3 on creeks, 7 on ponds and 320 are groundwater stations.

Presently the inland water quality monitoring network is operated under a three-tier programme i.e. Global Environment Monitoring System (GEMS), Monitoring of Indian National Aquatic Resources System (MINARS) and Yamuna Action Plan (YAP). Water samples are being analysed for 28 parameters consisting of 8 core parameters, other physico-chemical and bacteriological parameters apart from the field observations. Besides this, 9 trace metals and 22 pesticides are also analysed in selected samples. Biomonitoring is also carried out on specific locations. In view of limited resources, limited numbers of organic pollution related parameters are monitored i.e. micro pollutants (Toxic Metals & POPs) are analysed once in a year. The water quality data is reported in Water Quality Status Year Book.

The water quality data on rivers, lakes, ponds, tanks and groundwater locations being monitored under the network is evaluated against the water quality criteria and the monitoring locations in exceedence with respect to one or more parameters are identified as polluted indicating need for action to restore water quality. Brief details of locations on rivers, lakes, ponds, tanks and groundwater not meeting the criteria are given below.

• Total percentages of observations having BOD less than 3 mg/l, 3 to 6 mg/l and above 6 mg/l were 66%, 19% and 15%, respectively. The total percentage of observations having Total Coliform number less than 500 MPN/100 ml was 44%, between 500-5000 MPN/100 ml was 34% and exceeding 5000 MPN/100 ml was 22% MPN/100 ml. Similarly the percentage of observations having Faecal Coliform bacterial count less than 500 MPN/100 ml was 59%, between 500-5000 MPN/100 ml was 27% and 14% observations were exceeding 5000 MPN/100 ml.

• Fecal coliform, another important indicator of pollution, was found to be the highest in Yamuna River in Delhi (MPN 3.9 x10⁷) followed by River Hindon after confluence with River Krishni (2.1x10⁶), River Ganga at Dakshineshwar (7x10⁵), Rabindrasarovar, Kolkata (8.5x10⁵), River Damodar at Haldia (4x10⁵), River Khari at Lali Village, Ahmedabad (2.8x10⁵), River Sabarmati at Ahmedabad (2.4x10⁵), River Bharalu, Assam (2.4x10⁵), River Ganga at Varanasi ((1.1x10⁵), River Satluj at Ludhiana (0.9x10⁵), River Tapi at Bhusaval (9x10⁴), River Kalinadi at Muzaffarnagar (9x10⁴), River Ghaggar (9x10⁴), River Sabarmati at Ahmedabad (7.5x10⁴), River Gomti at Lucknow (7x10⁴), River Godavari at Nasik (5x10⁴) and River Musi at Hyderabad (4x10⁴).

• Lakes and Tanks that have high concentration of organic matter and do not comply to the standard limits for BOD are Hussain Sagar lake, Dharamsagar tank, Bibinagar lake, Kistarareddypet tank, Saroornagar lake, Pulicate lake, Gandhigudem tank, Heballa Valley lake, Kayamkula lake, Kodungalloor lake, Osteri lake, Bahour lake, Udhagamandalam lake, Kodaikanal lake, Periyar lake, Vembanad lake, Ashthamudi lake and Paravur lake. Lakes and Tanks having very low DO and high BOD that does not meet the water quality criteria limits are Kankoria Lake, Chandola lake, Pichola Lake, Udaisagar lake, Fatehsagar lake, Kayalna lake, Nakki lake, Pushkar lake, Lower lake Bhopal, Renuka lake, Harike lake, Naini lake, Ramgarh lake, Rabindra Sarobar lake, Elangabeel System, Goy Sagar Tank, Loktak lake at Sendra, Umiam lake at Barapani, Ward Lake at Shillong, Thadlaskena lake and Laxminarayan Bari Place Lake.

• The groundwater monitoring locations, where high conductivity exceeding water quality criteria for irrigation were observed at Ramagundam, Bollaram Panchayat Office, Pashamaylam, Vishakhapatnam (near Rama Temple) and Kakinada (near Pratap Nagar Bridge) in Andhra Pradesh; Nerol in Gujarat; Alwaye in Kerala; Circuit house, old police Barracks, Ottavathilpalli, near Helipad, MPSAF Quarters and Government Press in Lakshadweep; along Chunamber river in Pondicherry; and Pali, Jodhpur and Vidhani Village (Jaipur) in Rajasthan. Groundwater locations with BOD levels higher than the criteria are at Vijayawada, NTPC ash pond- kundanpally, Bibi nagar Primary school, Rudravally, near Tungabhadra river in Kurnool and Nandyal in Andhra Pradesh; Karbianglong and Bongaigaon in Assam; Kala Amb, Barotiwala and Paonta Sahib in Himachal Pradesh; JB School, Kadatpalli, near SB School, Ottavathilpalli and Chakikilum in Lakshadweep; Collector Well in Thirupuvanam and along Chunamber river in Pondicherry; near Kansua Nallah in Kota, Pali town, Jodhpur in Rajasthan; IOC Refinery Haldia, Barasat municipality in north 24 Parganas in West Bengal. Total coliforms are exceeding the criteria limits in groundwater locations in Silcher, Barpeta, Bongaigaon, Sibsagar, Guwahati in Assam, Chekkillam, Government press and old Police Barrack in Lakshadweep. pH is observed in acidic range at Kundra in Kollam, Punkunnam in Trissur, Kalamassery in Ernakulam, Punalur and Kannur in Kerala; and Capital hospital in Bhubaneshwar Orissa.

Central Pollution Control Board is regularly monitoring entire 1376 km stretch of River Yamuna under National River Conservation Directorate (NRCD/MoEF) sponsored project and under National Water Quality Monitoring Programme (NWQMP). There are19 sampling locations from the origin of Yamuna River at Yamunotri to its confluence with Ganga River at Allahabad. The entire stretch of Yamuna River can be segregated into five distinguished segments/ stretches based on water quality, ecological and hydro-geo-morphological characteristics. These stretches are Himalayan stretch, Upper Stretch, Delhi Stretch, Mixed stretch & Diluted Stretch. The water quality characteristics in these stretches of River Yamuna are depicted in Table below.

Bio monitoring of various rivers was undertaken in the state of Uttaranchal for water quality assessment using Biological Water Quality Criteria (BWQC). Out of 63 river stretches studied in Uttaranchal State, 47 river stretches were found clean, 4 river stretches were slightly polluted, 4 stretches were having moderate pollution and one stretch was heavily polluted. Besides, 7 numbers of river stretches were severely polluted as indicated by total absence of benthic macro-invertebrates because of the activities of Hydro-electric power generation project on River Bhagirathi, River Dhauliganga and River Ramganga.

CPCB has initiated groundwater quality surveys in large urban centers (Metro-cities) in collaboration with National Institute of Hydrology, Roorkee, and Pollution Control Research Institute, BHEL, Haridwar. The study includes collection of information of land use, waste generation & disposal & collection of water samples from different locations in the city from structures (Hand pump, Tube well, or Dug well) and analysis of relevant water quality parameters. So far study of 24 metropolitan cities have been completed and reports on 8 metropolitan cities have been finalised.

The maximum range of chloride concentration (above 1000 mg/L) in groundwater is observed in Chennai Metropolitan city followed by Vijaiwada, Madurai, Coimbatore, and Agra. Total dissolved solids are observed in very high range in Chennai followed by Vijaiwada, Coimbatore, Madurai and Agra. The Nitrate concentration in the three metropolitan cities -Agra, Coimbatore and Meerut – is observed above the permissible limit whereas in the remaining cities - Lucknow, Ludhiana, Vijaivada, Chennai, and Madurai – it is observed within the permissible limit. The concentration of Fluoride at Agra, Vijaiwada, Chennai, Madurai and Coimbatore metropolitan cities are observed above the permissible limit of drinking water whereas remaining three cities, it was found within the permissible limit. Bacterial quality of groundwater, which is indicated by the Coliform bacteria, was found adequate in all cities except for Lucknow and Meerut Metropolitan cities.

Groundwater quality with respect to compliance status with respect to drinking water standards (IS-10500, 1991) of the critical chemical parameters such as Chloride, Total dissolved solids (TDS), Nitrate-N, Fluoride are presented in Figure below.

Groundwater quality has been monitored at 15 major cities in Madhya Pradesh, Rajasthan and Chhattisgarh states selecting five cities in each state. Samples were collected from tubewells, handpumps and open wells, two locations in each category covering residential areas, industrial areas and municipal waste dumpsites in each city.