Tunnel Wells, the Traditional Water Harvesting Structures of Kasaragod, Kerala: Re-Visited

Tunnel wells or surangams are less common traditional groundwater harvesting structures of Kasara-god district in Kerala, southern India. These horizontal wells, structurally resembling Qanats, are driven into the laterite plateaus and hills for tens of metres. The status of tunnel wells of Kasaragod is synthesized, the problems and prospects examined to evolve a common strategy for sustainability. Functionally four different types of tunnel wells exist: (1) single tunnel, (2) single tunnel with branches, (3) tunnel system ending in a vertical well, and (4) tunnel system ending in a well with a horizontal outlet. The yield of tunnel wells has reduced over the years and 50% of them are now dry. Single tunnels (types 1 and 2) act as conduits for excessive draining of groundwater from the aquifer system during the rainy season, leading to wastage of groundwater and lowering the water table. The discharge estimates from the 24 tunnel wells indicate that 6653 m³ of groundwater gets discharged from the aquifer per day.To prevent wastage, the mouth of the tunnel wells should be fitted with half shutter gate with a control valve at the bottom. There is an urgent need to create awareness to protect and modify these traditional water harvesting structures for sustainability of water resources.