Development of a 3D Geological Mapping and Database Interface to Support Interconnected Groundwater and Surface Water Management

This project demonstrates an approach for coordinating hydrogeological data to improve the management of water in a catchment. Developed for this project are a series of Mathematica applications that help with the improved visualisation and interpretation of catchment water data, in particular advancing the way we spatially analyse standing water level information and driller logs. The new visual methods help with conceptualising the catchment hydrogeology, and guide the construction of catchment water balance models. Data available from the Bureau of Meteorology (BOM), Geoscience Australia (GA), various state water departments, Catchment Management Authorities and new data collected as part of this project have been coordinated into two databases; one for continuous data, point information and bore details, and a GIS database for all 2D information. Information is extracted from the databases for examining trends in borehole and stream hydrographs, generating 2D and 3D graphical representations of the data and trends, and for constructing a 3D geological conceptual model of a catchment. These 3D models and hydrograph data are then passed to any surface water and groundwater modelling environment. FEFLOW was used for this project. The NSW State Government distributes historic water information on the “Historic data CD Pinneena for Groundwater Works”. Mathematica notebooks have been written to provide a graphical representation of the data. Detailed in the notebooks are methods for plotting individual bore hydrographs, automatically plotting all hydrographs within a geographical area, performing time-series analysis, examining the correlation between two hydrographs (for example, a post processing FEFLOW model output, comparing the modelled versus the measured groundwater hydrograph), plotting in 3D the change in the recovered standing groundwater level for all monitoring points in a catchment, examining in 3D the impact of groundwater extraction in any pumping season, and plotting an interpretation of the driller log descriptions in 3D (a facies model of the unconsolidated sedimentary valley-fill). A major outcome of this project has been the development of a new approach for constructing 3D geological models of catchments. New scripts have been written in the Mathematica scripting language that enables the construction of 3D geological structural and property models. The structural model provides the boundary surfaces for the groundwater flow model (the ground surface and the palaeovalley surface) and the property model provides the permeability distribution for the groundwater flow model. The 3D geological models can be used to determine the volume between any surfaces, or to present the most likely lithology to be encountered when drilling a new bore. The Mathematica notebooks will be marketed under the name Crystallize. The Crystallize notebooks take advantage of the extensive library of functions in Mathematica and add new algorithms needed for hydrogeological investigation. Mathematica notebooks are interactive documents. Each notebook consists of text, links to databases, algorithms, plots, 2D and 3D graphics. Pages in the notebook look like normal text. The scripts that form part of the document can be run from within the document, and the plots and 3D graphics that are generated in the document can be manipulated and edited within the notebook. All 3D objects within the documents can be rotated, allowing the 3D geological models to be viewed from any position in space. Consolidating the base hydrogeological data into MS Access and ArcGIS is a well documented standard practice. However, there is still much development required on how to construct 3D geological conceptual site models, and how to transfer the detail captured in the high resolution 3D geological model into the relatively coarse scale coupled surface water and groundwater flow models. Worldwide there are no standardised approaches on how to construct a 3D geological framework for coupled surface and sub-surface water flow modelling. There are many new 3D geological and water balance modelling environments available, evolving and emerging. An advantage of the approach presented in this project is that the Crystallize notebooks can be easily modified or new scripts added by any individual. FEFLOW is one promising application for examining aspects of the catchment water balance. This project explored the capacity of FEFLOW for evaluating the catchment water balance. The adopted approach incorporated more hydrogeological complexity and details about plant water use than many models presently used throughout the Murray-Darling Basin. A goal of this project was to have more layers in the FEFLOW model to capture the facies variability in the unconsolidated sediments (ideally a layer for the typical thickness of the lithological layers, in the order of 5 m within the Maules Creek Catchment). This is important for the objective of modelling the migration pathway of groundwater where there is substantial variability in the water chemistry. However, if FEFLOW calculations within the order of hours are required then the aquifer geometry needs to be simplified. The final FEFLOW model had layers set to represent the deep drainage surface, a vertosol layer, and then approximately every 20 m throughout the deepest portion of the aquifer system. Further research is required about how to best represent an aquifer in a groundwater model for fast calculations. More hydrogeological complexity could be incorporated into future models by either using a more powerful computer than used for this project or by allowing the calculations to run for a day or more. The data analysis methodologies developed as part of this project have already been used in student projects at The University of New South Wales (UNSW), for Cotton Catchment Communities CRC projects, and by the Water Research Laboratory (WRL) at the University of New South Wales for baseline assessment of groundwater conditions for the Namoi Catchment Management Authority. The methods developed as part of this project make 3D geological modelling and hydrograph analysis accessible to all government agencies, contractors, and research institutions. In particular, students now have access to 3D geological modelling and hydrograph analysis software that they can use at home and throughout their careers in groundwater management. This project has considerably advanced our conceptualisation of river and aquifer connectivity in the Maules Creek region and demonstrated the impact of the groundwater irrigation extractions. Presentations of the results at cotton industry forums and trade shows and at community meetings have all been well received, often giving irrigators a new understanding of surface water and groundwater processes.