Abstract This study evaluated the suitability of Storm Water Management Model (SWMM) for continuous rainfall-runoff modelling and investigated the Event Mean Concentration (EMC) approach in quantifying total nitrogen (TN) and total phosphorus (TP) wash off to the Maribyrnong river in Australia. The model demonstrated satisfactory performance for stream flow simulation during calibration (R 2 = 0.551, NSE = 0.522, KGE = 0.724, PBIAS = 3.96%) and validation (R 2 = 0.6695, NSE = 0.603, KGE = 0.503, PBIAS = 19.03%). For water quality, only TN concentrations in streamflow were satisfactorily validated (R 2 > 0.30 and PBIAS < ± 70%). Further, correlation analysis revealed the intricate role of land use in nutrient dynamics, highlighting the multi factor interdependency on runoff volume, wash off concentration and land use characteristics. Results suggest that SWMM can be effectively used for large scale, spatially heterogenous catchments, provided careful parametrization and calibration are undertaken. While correlation analysis supports the validity of EMC transferability, validation of TN concentration show less sensitivity to temporal pattern, highlighting the need for development of dynamic EMCs.

Abstract Saltwater intrusion (SI) increasingly jeopardizes coastal aquifers, causing soil and groundwater salinization. Subsurface dams are commonly installed at the aquifer base to counteract SI. They have proven to be highly effective mitigation measures, albeit costly. However, such concrete dams often imply inherent construction defects in addition to cracks that are highly likely due to chemical interaction with dissolved ions. An appraisal of the efficiency of fractured subsurface dams is therefore essential for a comprehensive impact assessment and the planning of proposed countermeasures. Accordingly, the SEAWAT code was applied to simulate the abilities of variant configurations of dam heights and locations with different aperture dimensions to control SI. Application in the Henry problem and the Biscayne Aquifer, USA, permitted a consistent appraisal for benchmark and field-scale groundwater systems. Alteration in invasion length at the aquifer base was the key parameter for assessing the performance drop attributed to fractures. The loss of effectiveness was higher in short, defective dams, which permit the flow of dense saltwater through fractures. Similarly, the closer a dam was located to the shoreline, the higher the loss of efficiency observed. The loss of dual-fractured dam efficiency ranged from 4.70 to 75.96%, and the loss is highly sensitive to the dam location, fracture length, and lower fracture height, while fracture aperture indicated moderate sensitivity, and the upper fracture height indicated a lower sensitivity. Considering the study findings is imperative for the robust management of coastal aquifers. Exploring advanced materials and construction techniques to enhance the durability and reliability of subsurface dams is recommended.