US EPA

1841056 

Journal Article 

The Development of an Integrated Modelling Framework for Assessing the Impacts of Land Use Change on Corner Inlet 

Adams, R; Western, AW; Law, S; Andersen, S 

2009 

18TH WORLD IMACS CONGRESS AND MODSIM09 INTERNATIONAL CONGRESS ON MODELLING AND SIMULATION: INTERFACING MODELLING AND SIMULATION WITH MATHEMATICAL AND COMPUTATIONAL SCIENCES 

3449-3455 

WOS:000290045003071 

The E2 modelling system is a powerful software tool developed to enable catchment managers and planners to investigate the interactions of land use, climate, water quality and water quantity. E2 forms the basis of a Decision Support System (DSS) developed for the Corner Inlet catchment in South Gippsland, Victoria. The purpose of the DSS is to inform catchment management, via modelling of the terrestrial and estuarine impacts of scenarios of land use or land management change. This is achieved by linking together an E2 model of sediment and nutrient delivery from the catchment with a model of estuarine water quality impacts derived from detailed 3-D hydrodynamic simulation of the estuarine transport. The model can be used to run scenarios of land use or land management change in the terrestrial catchment (e.g. reforestation) with the results being examined for impacts on the estuary or on the modelled streams. The underlying hydrodynamic model was developed using MIKE21, and calibrated against gauged tidal records at 5 different locations throughout Corner Inlet and Nooramunga. Model parameters were calibrated in an effort to minimise differences between the measured and modelled water surface elevations and tidal constituents (amplitude and phase angle). The calibrated and measured tidal constituents were also verified against the Australian National Tide Tables and those reported in the literature. The IOS (Institute of Ocean Sciences) method was applied for the decomposition of tidal constituents. The advection-dispersion simulations of the estuary were analysed to develop a statistical link between constituent inflows and transport to important seagrass beds. This transport was treated as conservative due to limited data on nutrient transformations within Corner Inlet. For similar reasons, the State Environment Protection Policy was used to define critical water quality thresholds in Corner Inlet. The hydrological and water quality models within E2 have been used in this particular E2 application. The SimHyd model was used to simulate the rainfall-runoff response, with calibration against existing stream flow stations and fitting of separate parameter sets for forested and non-forested landuses. Existing monitoring data from various sources were used to parameterize and calibrate "constituent" models within E2 for nitrogen (Total Kjeldahl Nitrogen, NO(x)), phosphorus (Total Phosphorus, Dissolved Reactive Phosphorus) and suspended sediment generation. The choice of constituents for this study came about partly over concerns that elevated concentrations of nitrogen in the estuary were causing a decrease in the seagrass population in Corner Inlet. Concern has also been raised for several decades that high levels of phosphorus in coastal waterways in south-eastern Australia may contribute to the development of algal blooms and coastal eutrophication. A review of the existing data sources found that although the database of weekly and monthly water quality samples was reasonably extensive spatially (especially for Phosphorus) and covered a period of at least ten years of monitoring, the monitoring data lacked sufficient samples taken at high flow periods, classified as runoff events. Evidence from the samples taken during events was that the loads of nutrients and sediments transported during high runoff periods contributed over 90% of the total monitored load. Also, there was a paucity of nitrogen (including nitrate and ammonia) measurements in this particular catchment. Therefore, a monitoring program was devised to collect water quality samples from six streams and rivers at eight locations using automatic samplers. The data collected have been used to improve the calibration of the E2 model, especially for high-flow periods. 

Eutrophication; Decision Support Systems; Nutrient Modelling; Hydrodynamic Modelling 

Newham, LTH