A Study of groundwater recovery following tunnel construction in the upper highland complex – a case study on the Ranwediyawa tunnel

Abstract

In Sri Lanka, understanding the hydrogeological conditions is vital when constructing tunnels, especially geological regions such as the Highland Complex, where groundwater supports local communities and agriculture. While some recent data sheds light on groundwater reduction during tunneling, little is known about the recovery process. The Ranwediyawa tunnel construction, part of the Mahaweli Water Security and Investment Program (MWSIP), offered an opportunity to monitor groundwater impact closely. During excavation, considering seasonal variations, a reduction in groundwater levels was recorded, and following tunnel completion and installation of the waterproof lining, the groundwater recovery was monitored. The hydrogeological conditions of the Highland Complex present unique challenges as groundwater is vital for local communities and agriculture, so tunneling activities must be carefully managed to minimize disturbance. This paper outlines the planning, monitoring, and construction carried out for this project. Our findings stress the importance of comprehensive planning and monitoring during tunnel construction, understanding hydrogeological conditions and implementing effective waterproofing measures, to minimize environmental impact and ensure no disruption in domestic water supply and agriculture sustainability. It is hoped that the data and insights gained from this project can be used in future tunnel projects in similar hydrogeological settings, enhancing infrastructure project resilience and safeguarding groundwater resources for future generations.