The Gnangara Mound is an important source of water for public water supply, irrigated agriculture, parks and gardens, industry and groundwater dependent ecosystems.
Groundwater levels across the Gnangara Mound have generally been in decline for the last thirty years. This coincides with a general trend of declining annual rainfall across the south west of Western Australia. Groundwater level measurements have been recorded and averaged to produce a single average figure per month. Groundwater levels depicted on the graph are based on data taken from over 50 bores located across the mound's superficial aquifer. These bores were selected from the existing monitoring network on the Gnangara Mound, located between the Swan River in the south and Gingin Brook in the north with a minimum of ten years of data.
To achieve the single monthly average figure, monthly water levels are offset against the highest historically recorded groundwater level for each bore. These offset monthly water levels are then averaged across all the selected 50 bores to produce a single number. This single number represents relative groundwater level change across the Gnangara Mound compared to the average highest recorded groundwater level.