Australian User Group Clearer water for Bathurst with the help of QGIS and heat mapping Alexander Mackenzie GIS Officer, Bathurst Regional Council, New South Wales 31st August 2017 Introduction: The Bathurst Region is located 200 kilometres west of Sydney, in the Central West region of New South Wales. The Local Government Area (LGA) covers 3821 square kilometres and contains a single urban centre, the city of Bathurst, surrounded by rural land with several outlying villages. The LGA has a population of about 43,000, of which 86% reside in the city of Bathurst. The city of Bathurst is the oldest inland settlement in Australia, established as a town site in 1815 on the banks of the Macquarie River and growing into a city with the discovery of Gold in the nearby villages. Bathurst is probably best known as the home of the iconic Mount Panorama Motor Racing Circuit, which hosts an array of motor racing events through-out the year, including the popular Bathurst 1000 in October. Bathurst Regional Council (BRC) is responsible for services to the community such as water provision, waste and wastewater management, roads and infrastructure, development control and strategic planning. BRC also manages a number of historic sites, museums, community facilities and sporting venues (including Mount Panorama) throughout the city and surrounding region. The project: Bathurst Regional Council is responsible for providing clean and clear drinking water to the city of Bathurst. This water is extracted from the Macquarie River, which is supplied by the nearby Chifley Dam and Fish River; the raw water is then treated by council’s Water Filtration Plant to produce drinking water which complies with the Australian Drinking Water Guidelines. Over the years council had received a high number of calls from residents complaining of discoloured water. The discolouration was found to be caused by the presence of manganese; a naturally occurring compound in the soil of the Chifley Dam and Fish River catchment area. Although safe to drink, the water could have an unpleasant appearance and may cause staining of laundry. There are substantial technical difficulties with removing the manganese from the water. Plus any buildup of manganese within the pipe network could dislodge at times of high demand or when breakages occur, causing inconvenience to customers.

Figure 1 – Discoloured water complaints (anonymised).

Council committed to resolve the problem though the Manganese Removal Project, which would see significant upgrades to the Water Filtration Plant and the identification and removal of manganese that had built-up in the city’s network over its more than 120 years of use. As a part of the project the GIS Section was tasked with identifying potential areas of manganese buildup in the system. This was achieved by first using QGIS to geocode 5 years of discoloured water complaints from council’s CRM system, using a combination of address data and coordinates recorded with the CRM records. This produced a point dataset with about 3,000 points (Figure 1). Displaying the points in QGIS immediately showed that there were definite areas of clustering. However it is easy to miss trends that may be hiding in the mass of vector points, especially when many overlap. So to better understand where the buildups of manganese may be located we installed the Heatmap Plugin for QGIS from the Plugin Manager. The Heatmap Plugin uses a Kernel Density Estimation to generate a raster layer where the cell value is determined by the number of points that are within a given search radius, more points in the search radius will return a higher cell value. The resulting raster Figure 2 – Heatmap of discoloured water complaints. was then displayed within QGIS with a psuedo-colour styling; low density values shown as blue, mid density as yellow and high density shown as red, creating a clear and dramatic representation of discoloured water ‘hotspots’ (Figure 2). Conclusion: As a part of Bathurst Regional Council’s Manganese Removal Project, QGIS was used to quickly map our existing CRM data as vector points and then generate a heat map of the discoloured water complaints that council had received over several years without the need to purchase additional software or expensive add-ons. The resulting heat maps enabled us to better target areas of Bathurst’s water network for further investigation and then assign water crews to exhume pipes in the hot spot areas. More often than not the hot spots on the map correlated with issues of high buildup of manganese in the network. QGIS proved to be an important tool in this project; saving time, cost and effort and ultimately resulting in clearer water for the residents of Bathurst. Bathurst Regional Council has since used the Heatmap Plugin in QGIS to identify areas of ongoing issues in Council’s sewer network, so that they can be better targeted in our maintenance program.

Alexander Mackenzie

31st August 2017