Detection of Ground Water Reservoirs in Pyroclastic Rocks by Using Geoelectrical Method (Case Study: Kal Area, South of Damavand)

Due to the decreasing of the groundwater level in most plains of our country and increasing water demand, recognizing groundwater reservoirs in hard formations, especially non-carbonate rocks, is of the special importance. Kal area is located in the south of Damavand city. In order to recognize groundwater reservoirs, fifteen vertical electrical sounding with Schlumberger array configuration and a maximum length of the current transmitter of 1500 m were performed and then the field information were processed. .Based on geoelectrical findings in this area, five geological layers including debris and alluvium sediments with resistivity from 35 to 110 Ωm, Hezar darreh conglomerate formation with resistivity from 15 to 60 Ωm, upper Tuff layer with resistivity from 50 to 100 Ωm, lower Tuff layer with resistivity more than 60 Ωm and a middle crushed middle Tuff layer with resistivity from 40 to 50 Ωm layer have been recognized. Along the cross section B-B, a buried underground fault has been recognized that activity of this fault has caused crashing in Tuff layers in this area. The crashed Tuff layer contains groundwater in depths between 50 to 100 meters and drilled water wells in this zone contain more yield rather than other exploitation wells in this area, and also soundings of no. 2, no. 3 and no. 8 contain better yield potential. Geoelectrical studies in this area indicated that igneous and pyroclastic rocks can be considered as new resources to provide drinking water for the region.