GIS Base Mapping of Groundwater Aquifer and their Movements in Horana Divisional Secretariat Division.

The favourable water aquifers serve as critical water resources for agricultural, industrial and domestic purposes. Understanding the distribution, movement, and potential of saturation ability of these aquifers is essential for efficient water management and planning. Horana Divisional Secretariat Division (DSD) has different thickness water aquifer layers perpendicular to the soil structures and topographical variations. The present research aims to analyse the groundwater aquifer and its movements by analysing geographic information systems (GIS). The mapping of groundwater aquifer characteristics and movement patterns, interactions were analysed using geophysical data, the dug well depths and geological information. The electrical sound resistivity (VES) method was used to identify each layer using resistivity (ohm - m) (Ω) values, which were collected from the local provincial council (Western Province) applied survey project reports. The 27 dug well points were measured using measuring tape to verify the water aquifer layers' depth values, as well as soil percolation test, and their rates were calculated using the “(cm/hour)” method (Joleha et al., 2023). The USGS satellite image was downloaded to prepare the digital elevation model (DEM). The 100m contours and the groundwater flow direction map were prepared by the dug well location depth with contours using ArcGIS 10.4.1 software. The result indicates a clear relationship between dug well depths and resistivity valves, which shows topsoil, not saturated, water saturated, weathered and fractured bedrocks and bedrock layers. The dug well depths showed the water aquifer depths in the research area. Contours and dug well depths were used to prepare the groundwater flow map. This flow pattern linked the topography of this area. The above finding mentioned that groundwater storage, capacities, layers and flow patterns can be mapped using the ArcGIS application. According to the area aquifer and flow patterns, the analysis will help with the groundwater exploration and its planning in the Horana (DSD) area.