A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 2002

Groundwater exploration, development and conservation are of significant importance to developing countries, which often face shortages of surface water resources to meet their demand. Taking this into account, an assessment of groundwater resources in Walawe River basin, Sri Lanka has been conducted based on the available groundwater quality and quantity data. This study focuses on providing an approach to initiate the institutional framework for the future studies proposed in Walawe Basin by committing resources to develop and maintain long-term research activities in the basin. Groundwater data and references were collected from a large number of sources and the collected data were combined to produce a single groundwater data inventory for the Walawe basin. The geostatistical analysis of groundwater quality was carried out in the study area and it shows that the water quality is not so spatially varied. The critical zone maps for Fluoride, Iron and Total Hardness show that these chemical parameters are found in some places beyond their permissible limits for domestic use. Three well-known methods for measuring groundwater vulnerability were applied to determine the groundwater vulnerability of the area with respect to groundwater quality and quantity; DRASTIC, CAER and susceptibility for groundwater level decline. A mapping evaluation of all methods using GIS environment, concluded that all methods appear applicable for the study area. Finally, a monitoring network design is provided based an nine alternative networks. Minimization of cost of construction and reduction of mean kriging standard deviation were considered as major criteria for selection of the best network system among the alternative networks by using multi-criteria decision making.