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Understanding More about The Water Balance and Origin of Vellayani Kayal: A Coastal Wetland Located in South Kerala

Sundara Rajan CV, Jesse BF and Praveenkhanna U

Several studies were carried out featuring various aspects of Vellayani Kayal; an important wetland and a perennial source of fresh water in the southern part of Thiruvananthapuram district, Kerala State. This is locally known as Vellayani Kayal (Vellayani wetland or lake) is located at 8°25'35.21"N and 76°59'35.87"E. The Vellayani Kayal is the major source of drinking water for the people of Kalliyoor, Venganoor and Vizhinjam gram panchayats. This is also important for food safety on account of paddy cultivation in the area. Over the years, this wetland has reduced in area. During monsoon season, large quantity of water is drained in to this lake and the water reservoir is protected with suitable spillway mechanism. There were few studies relating to various aspects of this important wetland. An attempt was made to compute the water balance by National Centre for Earth Science Studies (NCESS), now a Government of India (GoI) Research organization. In this paper, the water balance of the Vellayani Kayal is suggested to recompute considering the grey areas of water balance results derived by NCESS. Although NCESS tried to finalize the water balance equation, the assumptions behind the water loss and gain through inflows remained unidentified. The reassessment and analysis based on the new findings shall possibly provide the details of more accurate water loss and inflows. In the same context, the ambiguity behind the origin/source of this important wetland was also resolved paving way for better management of the lake and this precious water resource of the region. During 2013, as part of the study, the area has been mapped with the help of SoI topo sheets and satellite imageries coupled with very high level ground truth verifications for the sole purpose of augmenting the water supplies in the region. The geologic studies including lineament mapping using Remote sensing techniques were also helpful for identifying the origin and evolution of this important coastal wetland. This has ultimately resolved the issues and made possible to compute a more acceptable water balance.