The riverbed of Pampa has almost reached the base line or sea level owing to indiscriminate sand mining over the past three decades, leaving the Varattar riverbed far above it in its section west of Puthukkulangara-kadavu and hence deepening of the Varattar below the sea level will result in salinity intrusion, badly affecting the wells in the region, according to a preliminary environmental impact assessment (EIA) conducted by an expert team.
The EIA was conducted by a six-member team constituted by the Kerala State Council for Science, Technology and Environment (KSCSTE) on the request of the Haritha Keralam mission. The expert team was headed by the KSCSTE Member Secretary S. Pradeep Kumar.
The expert team comprising R. Ajayakumar Varma, Technical Advisor to the mission; Kamalakshan Kokkal, Senior Principal Scientist at KSCSTE; D. Padmalal, Senior Principal Scientist and Head of the Hydrology Processes Group at the National Centre for Earth Science Studies (CESS); P.S. Harikumar, Senior Principal Scientist at the Centre for Water Resources Development and Management, and P. Harinarayanan, Senior Scientist with KSCSTE.
The Varattar is a nine-km long rivulet originating from the southern part of the Aadi-Pampa and joining the Manimala river in the west. Aadi-Pampa is a double-headed meander loop of the Pampa (original channel course of the river Pampa), which was later short-circuited by flood waters.
Dr. Ajayakumar Varma told The Hindu that the Varattar had been part of the natural flood management system, carrying water across the Pampa and the Manimala rivers during floods. The fluvial system of Aadi-Pampa-Varattar was once very healthy and contributed to the water balance of a large area. However, both the channels were severely deteriorated owing to haphazard constructions, low causeways, encroachments, dumping of waste, and lowering of the Pampa and Manimala rivers owing to indiscriminate sand mining disrupting the flow, he said.
Dr. Varma said the degradation of these rivers started when the Pampa was subjected to rampant sand mining. The channel depth, which was less than 3 metres before 1990s, had turned to over 5 metres at many places. Studies conducted by the CESS team led by Dr. Padmalal also revealed that the Pampa riverbed was lowering at a rate of 10 cm a year owing to instream sand mining.
Deepening not recommended
The EIA has not recommended deepening of the fluvial system of Aadi-Pampa and Varattar as the experts are of the opinion that any deepening without augmented groundwater recharge may lead to lowering of the groundwater table in the off-channel areas. Instead, the riverbed of the main channels of Pampa and Manimala may be allowed to gain sediments by preventing river sand mining, thereby the Aadi-pampa loop channel and Varattar will have improved flood pulsing effect.
The EIA has recommended demolition of the causeways and other obstructive constructions across the fluvial systems so as to improve the channel flow, especially during the flood. The obstructive sandbars or mud heaps may also be removed for improving the flow.
The EIA also warned of aggravation of the hungry water effect in the event of deepening the channel through extraction of sediments.
