Modelling the effects of climate and land cover change on groundwater recharge in south-west Western Australia

Abstract

The groundwater resource contained within the sandy aquifers of the Swan Coastal Plain, south-west Western Australia, provides approximately 60 percent of the drinking water for the metropolitan population of Perth. Rainfall decline over the past three decades coupled with increasing water demand from a growing population has resulted in falling dam storage and groundwater levels. Projected future changes in climate across south-west Western Australia consistently show a decline in annual rainfall of between 5 and 15 percent. There is expected to be a reduction of diffuse recharge across the Swan Coastal Plain. This study aims to quantify the change in groundwater recharge in response to a range of future climate and land cover patterns across south-west Western Australia. <br><br> Modelling the impact on the groundwater resource of potential climate change was achieved with a dynamically linked unsaturated/saturated groundwater model. A vertical flux manager was used in the unsaturated zone to estimate groundwater recharge using a variety of simple and complex models based on climate, land cover type (e.g. native trees, plantation, cropping, urban, wetland), soil type, and taking into account the groundwater depth. <br><br> In the area centred on the city of Perth, Western Australia, the patterns of recharge change and groundwater level change are not consistent spatially, or consistently downward. In areas with land-use change, recharge rates have increased. Where rainfall has declined sufficiently, recharge rates are decreasing, and where compensating factors combine, there is little change to recharge. In the southwestern part of the study area, the patterns of groundwater recharge are dictated primarily by soil, geology and land cover. In the sand-dominated areas, there is little response to future climate change, because groundwater levels are shallow and much rainfall is rejected recharge. Where the combination of native vegetation and clayey surface soils restricts possible infiltration, recharge rates are very sensitive to reductions in rainfall. In the northern part of the study area, both climate and land cover strongly influence recharge rates. Recharge under native vegetation is minimal and is relatively higher where grazing and pasture systems have been introduced after clearing of native vegetation. In some areas, the recharge values can be reduced to almost zero, even under dryland agriculture, if the future climate becomes very dry

Potential climate change impacts on the water balance of regional unconfined aquifer systems in south-western Australia

“…In addition to rainfall the sensitivity of recharge and storage to climate change also depends, on land cover, soil types, water table depth as reported by Crosbie et al (2010), McCallum et al (2010) and Dawes et al (2012) for Australia and by Jyrkama and Sykes (2007), Liu (2011) and Green et al (2011) for other regions. Due to clearing in the north-east areas of the Central Perth Basin water tables are projected to rise substantially while they are projected to decline in most other areas.…”

Impact of lateral flow and spatial scaling on the simulation of semi‐arid urban land surfaces in an integrated hydrologic and land surface model

“…The influence of land cover/land use on the surface energy budget (SEB), runoff, and recharge rate is a significant topic of interest and has been shown to be especially influential given urban land cover/land use (Peters et al ., ; Dawes et al ., ; Barron et al ., ; Marciotto, ). The creation of urban canopy models (UCMs) within LSMs, largely to improve the lower boundary condition of regional and urban scale atmospheric models (Masson, ; Kusaka and Kimura, ; Wang et al ., ), has resulted in improvements in the representation and partitioning of evapotranspiration (ET) rates (Loridan et al ., ; Ramamurthy and Bou‐Zeid, ), land surface temperatures (Arnfield, ), and other variables of interest in cities.…”

A Practical, Robust Methodology for Acquiring New Observation Data Using Computationally Expensive Groundwater Models

“…The delineation of the mapped faults that may impact groundwater flow are depicted in Figure . Recharge, evapotranspiration, and other surface water processes are simulated using the Vertical Flux Manager (VFM) developed by CSIRO, which employs a number of various recharge and unsaturated‐zone flow models (Barr et al, ; Dawes et al, ). Discharge of groundwater in wetland environments is simulated as simple drainage (i.e., via the DRN package of MODFLOW).…”

“…Zonation is used as the primary parameterization device for the model. Parameters associated with the VFM were set to values based on both expert knowledge and the analysis of experimental data obtained in the field (CyMod Systems, ; Dawes et al, ; Silberstein et al, ), and were not estimated during this study. The resulting parameterization consisted of 417 individual parameters.…”