COASTAL GROUNDWATER INTAKES: NUMERICAL MODELING OF COASTAL WELLS FOR DESALINATION SOURCE WATER

摘要

A range of groundwater and surface water options were investigated to find an optimal source of saline water for a proposed coastal desalination plant (50 ML/day). Of particular importance in selecting the optimal location was the ability to maintain a constant intake water supply (quantity, temperature and salinity) as well as minimising costs associated with pre-treatment (filtering, intake redundancies, etc). As an alternative solution to ocean intakes, a range of groundwater intake options were investigated along a coastal dune system in New South Wales, on the eastern coast of Australia.To evaluate groundwater sourcing options from the site, a 3-Dimensional finite element model was developed and calibrated. A range of scenarios were undertaken to determine the optimal spacing, angle, length, number and depth of the lateral wells as well as the spacing, location and number of central caissons required. Model results indicated that four central caisson wells each with 5 laterals of 40-80 meters long spaced at 150 and 250 angles could supply the required water quantity. Importantly, by positioning the laterals towards the ocean, preferential flow from the ocean boundary limited drawdown on a sensitive lake boundary and provided optimal water quality outcomes. The natural filtering process through the coastal sands also reduced the amount of pre-treatment required. The application of discrete feature elements to simulate lateral wells has not been previously reported and is a significant improvement over previous analytical solutions.