Water Journal : Water Journal June 2015
June 2015 water 33 Feature article • A process to convert all data into a common and convenient format for producing hydrographs easily; • The means of storing data to allow easy access when required; • How to generate reports, either in an on-screen version or in pdf format, in a convenient way; • Information about the bores, aquifers they intersect, and relationships to each other; • The means to have all hydrograph and bore information readily accessible for analysis to enable better decision making; • The way to identify vertical aquifer interaction, i.e . between overlying and underlying aquifers in a stacked hydrogeological sequence. This last challenge of identifying aquifer interaction was another important aspect of interpreting regional behaviour. There are nested state observation bores located throughout Victoria, i.e. closely spaced bores that monitor different depth intervals within the lithological profile. By examining hydrograph behaviour at these nested sites, hydrogeologists can make determinations regarding inter- and intra-aquifer leakage, and how this may be influenced or modified over time. Identifying the nested sites and displaying characteristic hydrographs for the different aquifers was a key outcome of the project. approach To make the complex groundwater monitoring analysis process simple and efficient, by considering the problems and challenges described previously a robust methodology was adopted for construction and reviewing of groundwater level hydrographs. The methodology is divided into two components: Back-End Analysis and Front-End Interface. bacK-end analYSIS In the Back-End Analysis, a range of data such as bore water level data, water level suites, water extraction data, rainfall data and SOBN (State Observation Bore Network) database (comprising the bore information) were analysed and integrated into a single database to feed the tools for reporting ground trend dynamically and seamlessly. As shown in Figure 1, all processed data that are the results of a number of analysis (conducted using MATLAB, MS Access, ArcGIS and Python) were stored in an MS Access Database (point 2) to give easy access to the tools developed (points 3, 4 and 5) for hydrograph report generation. The Back-End Analysis can be split into a number of sections, which are described in the following sections. Making Same Scale and Remove Gaps To solve the issue of different ranges of water level, normalisation analysis was conducted to fit them into the same scale. MATLAB was used for this analysis and data was presented on a negative 30m to positive 30m ordinate axis (water elevation) scale range. MATLAB was also used to conduct linear interpolation analysis for removing data gaps and making data continuous. Figure 2 shows the process of normalisation and removing data gap process. Zonal Hydrograph To enable regional mapping and classification of groundwater level behaviour, a statistical analysis was conducted to create an average or characteristic hydrograph for an area that represents multiple hydrographs within that particular area – i.e. many ‘like’ hydrographs were converted into a single representative hydrograph. DELWP has grouped all of the monitoring bores into 258 categories of hydrographs exhibiting a like behaviour, which have been referred to as hydrograph suites. Statistical analysis was subsequently undertaken using MATLAB to generate an average hydrograph for each suite. The study also conducted a digitisation process to delineate the spatial extent of the suite across Victoria and across all aquifers, which enables users to see the smaller groundwater regions defined by their similar bore hydrograph. A set of rules was defined to support the digitisation process. Figure 1 Framework of hydrograph trend reporting. Figure 2. normalisation and removing gaps in the data.
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