Abstract
Growing social, as well as development activities in the premises of Sabaragamuwa University of Sri Lanka (SUSL) and its surroundings, have reformed the natural landscape of the area. Consequently, water demand is increasing. Therefore, an understanding of the subsurface geology and their potential as beneficial aquifers help to overcome the impending water demand because surface water scares in the area. In view of assessing the groundwater potential of the area, an initial study was conducted using topographic and satellite maps followed by a geo-electrical resistivity survey, consisting of vertical electrical sounding (VES) and electrical profiling. Results revealed three subsurface layers in most places. The resistivity of the topsoil layer is ranging between about 50 to 2800 Ωm and the average thickness between 1 m to 15 m. The second layer is characterized by resistivity between about 16 to 9760 Ωm. The resistivity of the third layer ranges from about 2 to 5600 Ωm, and extending to a depth of more than 100 m. Most of the curves were identified as K type. The rest of the curves were H, Q, and A types. Out of 18 VES points, nine locations were identified as possible locations for groundwater abstraction. Groundwater could be located at a depth of between 25 to 60 m. Resistivity data indicate that the regolith mostly forms the aquifers in the area along with some weathered rock aquifers at depth. Most of the points close to or at valleys were found to be deep aquifers. Considering all the geological, structural, and morphological features, nine locations were identified as most convincing and could be recommended for test drilling.
Highlights
Groundwater accounts for about 1% of the total water on the Earth and makes up to 35 times the amount of water in lakes and streams (Famiglietti, 2014)
Geological and geomorphologic methods and remote sensing techniques were carried out to identify possible locations for groundwater occurrence and electrical resistivity surveys were conducted focusing on those locations
The resistivity of the top layer ranging between 50 Ωm - 2800 Ωm and the average thickness between 1 m to 15 m
Summary
Groundwater accounts for about 1% of the total water on the Earth and makes up to 35 times the amount of water in lakes and streams (Famiglietti, 2014). More than two billion people around the world depend on groundwater as their main water source and for cultivation, half or more of the irrigation water relies on the groundwater sources (Famiglietti, 2014). Groundwater is significant from surface water due to several reasons. The chemical composition of the groundwater is stable. The storage of groundwater is always higher than the storage of surface water, and groundwater supplies are not severely affected by short period droughts. Biological contamination in groundwater is rare (Shankar, 1994; Siebert et al, 2010; Ojo et al, 2012)
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