Effects of Marikina Faults on groundwater

Abstract

Metro Manila faces a major shortage problem that will necessitate the development of all possible sources. Structural geological study is an effective tool in maximizing the exploration of water resources. The Marikina Faults, a permeable zone which could facilitate the movement and occurrence of groundwater should be fully evaluated for such purpose. The main objectives of this paper are 1) to study the effects of geology particularly the Marikina Faults on groundwater, 2) to evaluate the groundwater resources of the Marikina Valley area, and 3) to assist urban planners in the identification and assessment of geologically favorable sites for groundwater development. The Marikina Fault zone is composed of several geologic structures in the Marikina Valley at the eastern edge of Greater Manila Area (GMA). Geological studies indicate that the study area is controlled by two fault systems: the East and the West Marikina Valley Faults. Movements along these structures strongly influenced the morphology and groundwater conditions in the study area. Hydrogeological studies show that the groundwater is confined in the Pleistocene Guadalupe Formation, Quaternary Alluvium and along the fault zones. Geochemical data indicate that there are two types of groundwater (calcium bicarbonate and sodium-rich waters) within the Guadalupe Formation west of the West Marikina Valley Fault, and three types of groundwater (calcium bicarbonate, sodium-rich and sodium chloride-rich waters) within the Marikina Valley. The Marikina Faults facilitate the movement and circulation of groundwater. These have adverse effects, however, on groundwater quality as seepage of contaminated water is enhanced.