Lateral flow assessment in laterite terrain for better interventions in sustainable groundwater management

Laterite terrain overlying the charnockite bedrock system exhibits greater lateral movement of water as compared to its vertical infiltration into the soil profile due to partial water block. Furthermore, the topographic conditions in such areas play a crucial role in the movement of soil water. The variation in the precipitation pattern, increasing population and urbanization has contributed in reducing the infiltration opportunity time for rainwater. The present study was carried out at Malappuram district of Kerala in India. Though, the study area receives an average annual rainfall of 3 m, yet experiences high baseline water stress during post monsoon season. The research study involves analysis of lateral flow from three different soil profile depths i.e. 0-0.4 m, 0.4-0.8 m and 0.8-1.2 m under two different water inducement techniques. Lateral flow monitoring was carried out in two different experimental set ups in two different sites under simulated rainfall conditions and line source of water application. Variation in the lateral flow was assessed using capacitance based sensors which were calibrated and installed at all the three respective soil profile depths. The study revealed that though the infiltration capacity of laterite soil is quite high but, the major portion of infiltrated water moved as lateral flow without contributing to the groundwater table. It was found that of the total water applied as simulated rainfall about, 10 % accounted as lateral flow from a soil profile depth of 1.2 m. During line source application of water, out of the total lateral flow recorded, the soil profile depths of 0-0.4 m, 0.4-0.8 m and 0.8-1.2 m contributed portions of 52.3 %, 43.78 % and 3.8 % as lateral flow. It was found from the study that the soil physical properties including bulk density, effective porosity and soil texture governed lateral flow in the study area. Thus, the research study emphasizes on enhancing preferential flow in vertical direction through deep rooted flora in the study area.