THE KERAUGA CAVE AND LÆKJARBOTNAVEITA IN SOUTH ICELAND ‒ GROUNDWATER SAFETY AND HYDROGEOLOGY

This research looks at water protection of Laekjarbotnar and Kerauga springs in South Iceland. Discharge measurements show that Minnivalla- and Tjarnalaekur streams lose 350 and 1350 l/s respectively into the ground. The equivalent amount springs to surface along the edge of the Þjorsa Lava and Buði Glacial Moraine in a few springs. Tracer tests indicate that lost surface water of Minnivallalaekur transits partly along a fracture to Kerauga in 65 days and to Laekjarbotnar in 125 days through the Þjorsa Lava over a similar distance of about 5 km. Hence the lost surface water of Tjarnalaekur in the east is unlikely to travel past this drainage divide west of the fracture to Laekjarbotnar but more likely to drain into Ytri-Ranga. Thus a proposed poultry farm in that area proposes minimum direct risk to water safety of Laekjarbotnar. As a result of this connection Kerauga is not a safe source of drinking water. The aquifer is considered unconfined, heterogeneous and anisotropic. It is recommended to define inner and outer protection zones for Laekjarbotnar further north and to springs of Minnivallalaekur respectively. It is hypothesized that Kerauga cave is manmade.