A groundwater flow model was developed for the Maules Creek alluvial aquifer, in the Namoi Valley (NSW, Australia). The objectives were to provide a better understanding of the dynamics of the aquifer and to provide integrated modelling of the catchment water resources, including an assessment of groundwater abstraction. The model was developed using FEFLOW 5.4. The hydrogeological system is represented by 9 layers bounded by impermeable bedrock. The hydraulic conductivity distribution in the model was based on a 3D geologic model built with EarthVision® and Mathematica™ using bore logs from the area. Hydrologic stresses include diffuse recharge, irrigation recharge, stream-aquifer interaction, lateral groundwater inflow/outflow and groundwater pumping. The hydraulic head distribution for 1978, obtained from a steady state model, was used as the initial condition for the transient model which was run from January 1978 to April 2007. Model calibration was performed by a trial-and-error method based on matching modelled bore hydrographs with measured hydrographs. Overall the model performance is good with the model correctly capturing the recovered water levels after each irrigation season, as well as the long-term trends. However, in areas with large groundwater abstraction-induced drawdowns (up to 8-10 m) the seasonal dynamics are not captured well by the model. For assessing the effect of groundwater abstraction on stream-aquifer interactions, two scenarios were run: without groundwater pumping and with a 2-fold increase in the pumping rate. The baseflow fluxes to the river and water budgets were computed for each scenario and compared with the calibration scenario. The groundwater model has provided a better understanding of the alluvial aquifer system and its dynamics. The results show the impact of irrigation on the hydraulic head distribution and baseflow to the river. Limitations and possible methods of resolving model uncertainties and improving calibration performance were also investigated.
Using groundwater modelling to enhance the understanding of the Maules Creek alluvial aquifer, Upper Namoi, NSW.
GIAMBASTIANI, Beatrice Maria Sole;
2010
Abstract
A groundwater flow model was developed for the Maules Creek alluvial aquifer, in the Namoi Valley (NSW, Australia). The objectives were to provide a better understanding of the dynamics of the aquifer and to provide integrated modelling of the catchment water resources, including an assessment of groundwater abstraction. The model was developed using FEFLOW 5.4. The hydrogeological system is represented by 9 layers bounded by impermeable bedrock. The hydraulic conductivity distribution in the model was based on a 3D geologic model built with EarthVision® and Mathematica™ using bore logs from the area. Hydrologic stresses include diffuse recharge, irrigation recharge, stream-aquifer interaction, lateral groundwater inflow/outflow and groundwater pumping. The hydraulic head distribution for 1978, obtained from a steady state model, was used as the initial condition for the transient model which was run from January 1978 to April 2007. Model calibration was performed by a trial-and-error method based on matching modelled bore hydrographs with measured hydrographs. Overall the model performance is good with the model correctly capturing the recovered water levels after each irrigation season, as well as the long-term trends. However, in areas with large groundwater abstraction-induced drawdowns (up to 8-10 m) the seasonal dynamics are not captured well by the model. For assessing the effect of groundwater abstraction on stream-aquifer interactions, two scenarios were run: without groundwater pumping and with a 2-fold increase in the pumping rate. The baseflow fluxes to the river and water budgets were computed for each scenario and compared with the calibration scenario. The groundwater model has provided a better understanding of the alluvial aquifer system and its dynamics. The results show the impact of irrigation on the hydraulic head distribution and baseflow to the river. Limitations and possible methods of resolving model uncertainties and improving calibration performance were also investigated.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
