Abstract
Volcanic mudflow (Lahar) deposits, generated after the voluminous 1991 Mt. Pinatubo eruption, have caused disastrous damage in the Mt. Pinatubo area, including changes to the groundwater resources. Such changes prevented the recovery of agriculture. Consequently, we have applied an electrical survey to investigate groundwater in the disastrous area along Bamban and Pasig-Potrero river. Laboratory experiments were carried out to reveal the electric characteristics of the Lahar deposits and the former buried landsurface. We showed a relationship between water-saturation and sediment resistivity and estimated the resistivity of aquifers. Chemical analyses of groundwater showed thet groundwater with low resistivity contains high concentration of SO42- ions, especially in shallow layers of the Lahar sediments. The resistivity profiles indicate that the high resistivity zone corresponds to partially saturated sediments, and the low resistivity zone, underlying the high resistivity zone, to aquifers. Our study has demonstrated that groundwater depth and water quality in this area can be estimated using electical survey methods.
