Manning River Saline Dynamic Modelling

Client: Mid Coast Water (MCW)
Year: 2007/2008
Project Reference: 07055
WRL Technical Report: Manning River Saline Dynamic Modelling

The Water Research Laboratory undertook a numerical assessment of the long term impacts of different river flow regimes on the salinity distribution in the Manning River (NSW, Australia) for Mid Coast Water (MCW).

This modelling allowed an early-stage assessment of ecological impacts of extraction of freshwater from the downstream part of the Manning River system by both Mid Coast Water (MCW) and irrigators on the estuarine behaviour and saline profile of the Manning River system. In particular the ecological assessment provided a preliminary indication of whether the saline structure of the Manning River would change as a consequence of changing the extraction rates of water from Mid Coast Water (MCW) or irrigation; and whether environmental flow restrictions in the Manning should take into account ecological issues that arise from the movement of saline waters in the estuary as caused by water extraction.

The change of salinity due to river extraction, as opposed to that naturally occurring, is an important component of the understanding of the environmental impact that water extraction by Mid Coast Water (MCW) has on the Manning River. Hence, to assess the changes in saline dynamics between two scenarios (e.g. different extraction rules), the saline structure of long duration numerical model simulations has been compared. Therefore WRL developed and calibrated a daily inflow 1D hydrodynamics model (RMA-2) and a daily inflow 1D saline dynamics model (RMA-11) of the Manning River estuary.