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A joint study of the State’s groundwater resources conducted in 2017 by the Central Ground Water Board (CGWB) and the State Ground Water Department, after a gap of three years, has found that the net groundwater availability for the entire State is 5,211.75 million cubic metres (mcm). The figure ranges from 186.14 mcm in Idukki district to 591.44 mcm in Palakkad district, according to V. Kunhambu, Regional Director, CGWB.
This is against the net groundwater availability of 5,651 mcm assessed during the study conducted in 2013. Dr. Kunhambu said that as per the latest report, the annual groundwater extraction for all uses was 2,672.09 mcm, ranging from 56.78 mcm in Wayanad to 340.56 mcm in Thrissur. The annual availability of groundwater for domestic use up to 2025 would be around 1,571.28 mcm, ranging from 38.06 mcm in Wayanad to 254.99 in Malappuram. Extraction figures Groundwater extraction was found the highest in Kasaragod district (79.64%) and lowest in Wayanad (24.51%). Chittur block in Palakkad has been categorised as ‘overexploited’ and two blocks (Kasaragod block in Kasaragod district and Malampuzha block in Palakkad) have been termed ‘critical’. Thirty blocks are ‘semi-critical,’ while 119 blocks come under the ‘safe’ category, he said. According to Dr. Kunhambu, 18 ‘semi-critical’ blocks had been identified in 2013.
Now, as per the latest assessment, 12 more blocks come under this category. They are: Parakkadavu (Ernakulam), Elamdesam (Idukki), Kanhangad and Karadka (Kasaragod), Kondotty, Kuttippuram, Malappuram and Tirur (Malappuram), Thrithala (Palakkad), Nedumangad and Pothencode (Thiruvananthapuram) and Thalikkulam (Thrissur). A State-level committee has already approved the report, which would be of great help to planners serving as a guide for the optimal management of the State’s limited groundwater resources. Judicious development of groundwater and its scientific management was a must to ensure sustainability of the natural resource. Bacterial presence The report says the groundwater in phreatic aquifers is fresh and suitable for domestic, irrigation, and industrial uses. Isolated occurrence of brackish or saline groundwater has been observed, mainly in coastal districts, tidal estuaries, and streams.
Fluoride in excess of the permissible limits of 1.5 mg a litre has been observed in parts of Palakkad and in and around Alappuzha town. Iron and nitrate in excess of permissible limits were found in many areas, especially the midland ones. Bacterial contamination was observed all along the coastal area and was found more in Alappuzha, he said. Despite being blessed with ample surface water source and an average annual rainfall of 3,000 mm, the topographic settings of the State seldom allow adequate utilisation of this richly available water resource, said Dr. Kunhambu. Nearly 88% of the geographical area of the State is underlain by crystalline rocks devoid of any porosity with limited groundwater prospects.