Sasthamkotta lake in peril

T. Nandakumar, Thiruvananthapuram
The Hindu, October 28, 2015

Indiscriminate sand mining, unscientific construction and over-extraction of water have led to the depletion and environmental degradation of the Sasthamkotta freshwater lake, impacting on the biodiversity and groundwater availability in the region.

A study conducted by the National Centre for Earth Science Studies (NCESS) and the Cochin University of Science and Technology (Cusat) has found that instream and floodplain sand-mining over the last three to four decades had severely damaged the underground aquifers feeding the lake, affecting groundwater replenishment.

Spread over an area of 3.75 sq km, the Sasthamkotta lake is the major drinking water source for about 7,00,000 people in Kollam city and seven adjacent panchayats.

The report says the unscientific construction of an embankment on the southern side had isolated the lake system, cutting off the flood pulse of monsoon waters from the Kallada river which also acted as a biological corridor for aquatic animals to feed and breed.

The study, which analysed borehole cores retrieved from the floodplain areas of the Kallada river, revealed highly varied climate and sea level conditions that existed during the evolution of the lake, the largest freshwater body in Kerala and a Ramsar site since 2002.

According to the report of the study, which appeared in the latest issue of the Geosciences journal, the sand layers embedded within the alluvial sediments of the late Quarternary age (1.8 million years ago) acted as a major aquifer contributing a substantial proportion of freshwater to the lake system.

The authors, S. Vishnu Mohan, Sheikha E. John, Rajimol T.R., Maya K and D. Padmalal from the NCESS and Prof. Sajan K from the Cusat, point out that rampant removal of sand from aquifers using high-power pumps had affected the water balance of the lake.

Over-extraction of water is pointed out as another factor responsible for the depletion of the Sasthamkotta lake during the summer months.

Sand-mining

The report has called for immediate steps to regulate sand mining from the Kallada river as well as the floodplains of the lake. It also recommends an integrated effort to nourish the water potential of the region through scientific interventions both in the river and lake catchments.

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Rising sea level may hit 329 islands, including ones in Ernakulam

K.S. Sudhi
The Hindu, KOCHI,April 5, 2014 

The islands in Ernakulam Channel namely Willington Island, Ochanthuruthu, Appangad, Manjanakad, Vallarpadam, Thanthonnithuruthu and Mulavukad may be hit by rising sea level.

The researchers of the Centre for Earth Science Studies, Thiruvananthapuram, have bracketed these islands along with the other vulnerable ones in the backwater system of the State. They have estimated that as many as 329 backwater islands of Kerala are vulnerable to the impacts of Sea Level Rise (SLR).

The other islands identified in the region include the Komanthuruthu, Thevara, Nettoor, Maradu, Panampukad and Pizhala. Altogether, 33 islands in Ernakulam Channel have been identified as ones vulnerable to Sea Level Rise.

Kadamakudi, part of Mulavukad, Korumkotta, Moolampally, Cheranalloor, Kothad, Idakunnam and Chennur are also in the vulnerable list. Researchers have sounded alert that the islands of Kumbalanghi, Chattammel, Cheppanam, Valanthakadu, Kumbalam, Panangad located in Kaithappuzha Kayal in the city suburbs too may be hit by Sea Level Rise.

In Vembanad Lake, they have assessed 21 islands namely Pathiramanal, Anjuthuruthu, Amayadithuruthu and Perumbalam as the ones that may be hit by the rising waters. They feared that the extensive backwater system of the State including the “communities on the banks, ecosystems, low-lying filtration ponds, adjoining paddy fields and other infrastructure would face increased stress” due to the sea level rise.

The list has included the 25 islands in Ashtamudi Lake, 14 in the Periyar, 17 in the Bharathapuzha and 14 in the Valapattanam River among others.

The rampant reclamation of wetlands, including filtration ponds, could decrease the available area of flood plains and enhance the impact of sea level rise on the adjacent holdings, according to the scientific document prepared by the scientists.

A team of researchers led by K.V. Thomas of the CESS are working on a project for assessing the impact of Sea Level Rise and the identification of impact zones in the State. The Sea Level Rise, according to researchers, is of serious concern in Kerala which has a 590km-long coastline and large expands of backwaters and estuaries and low-lying areas such as filtration ponds.

Researchers pointed out that the presence of filtration ponds, which are low-lying areas, near many of the backwater islands increased their vulnerability. They pointed out the case of Sattar Island located in the Periyar River near Munambam, which was seriously affected during the tsunami in 2004.

The identification of the impact zone is crucial for planning mitigation measures and evolving adaption programmes.

 

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