Numerical simulations of river discharges, nutrient flux and nutrient dispersal in Jakarta Bay, Indonesia

• Full overview of river discharges, nutrient flux and nutrient levels in Jakarta Bay
• Important overview of nutrient flux from individual rivers
• Simulations identify the principal drivers of water circulation and nutrient gradient.
• Nutrient dispersion model includes the local effects of the Java Sea current system.

The present application of numerical modelling techniques provides an overview of river discharges, nutrient flux and nutrient dispersal in Jakarta Bay. A hydrological model simulated river discharges with a total of 90 to 377 m3 s− 1 entering Jakarta Bay. Daily total nitrogen and total phosphorus loads ranged from 40 to 174 tons and 14 to 60 tons, respectively. Flow model results indicate that nutrient gradients are subject to turbulent mixing by tides and advective transport through circulation driven by wind, barotropic and baroclinic pressure gradients. The bulk of nutrient loads originate from the Citarum and Cisadane rivers flowing through predominantly rural areas. Despite lower nutrient loads, river discharges from the urban area of Jakarta exhibit the highest impact of nutrient concentrations in the near shore area of Jakarta Bay and show that nutrient concentrations were not only regulated by nutrient loads but were strongly regulated by initial river concentrations and local flow characteristics.