Groundwater characterization in the Suquiapa river basin, Santa Ana, El Salvador

Abstract

The main investigated aquifer in the Suquiapa constitute the formation fractured lavas San Salvador or recent upper Pleistocene. Scattered in the study area 28 deep wells suggest the existence of permeable layers, which consist of alternating layers of clastic material alluvial and fractured lavas located at depths greater than 100 m. The main recharge area (45 Km²) constitutes the volcanic complex recent lavas of Santa Ana. Another very important fact that has been confirmed is the existence of two aquifers, the shallow aquifer is between 25 and 40 meters deep and the lower aquifer located approximately 80 to 120 meters deep. The hydraulic gradient varies from 0.01 to 0.026; storativity 0.001 to 0.1; transmissivity varies greatly, being, greater than 25000 m²/d and other very low, less than 100 m² / d very high values. The infiltration rate shows a marked difference between the southern area (near the volcano) with average values of 1.42 m / d; corresponding to sandy loam soils and the northern part (near the river Suquiapa) with average values of 0.10 m / d, associated with clay loam soils. Three hydrogeological units are recognized: fissured aquifer, porous aquifer and rocks of low aquifer importance; also a surface aquifer with a depth between 20 and 50 meters and a deeper aquifer about 100 meters deep. Applying the methodology Schosinsky, a water refill potential 71,8x10⁶ m³ / year in an area of 140 km² is determined.