Evaluation of AWRA recharge: Comparison to field recharge estimates across Australia

[摘要] This report describes three field based groundwater recharge estimate datasets including: 1) a long-term mean annual recharge dataset for 2282 0.05o AWRA grids (grid average estimated as the geometric mean of all available estimates within the grid) derived from 6343 individual point field estimates across Australia (majority of the data points have recharge estimates based on saturated and unsaturated zone chloride measurements), 2) annual recharge time series from 1970 to 2012 for 438 bores in South Australia and Victoria, and 3) monthly recharge time series from 2000 to 2002 for six sites in Tomago sand beds, New South Wales, as well as the modelled recharge dataset from the Landscape component of the Australian Water Resources Assessment (AWRA-L) model. The report evaluates the performance of AWRA-L in estimating groundwater recharge at 0.05o grids across Australia by comparing the estimates with point scale field estimates from the three reference datasets. The agreement in groundwater recharge estimates between the long-term mean annual dataset averaged at 0.05o grids and AWRA are reasonably good. The AWRA outputs are able to reproduce the spatial patterns and magnitudes similar to the averaged long-term mean annual recharge for all the combinations of rainfall, soil types and vegetation cover. For the annual recharge time series dataset, a few sites showed a reasonably good agreement between AWRA recharge estimates and the field estimates in South Australia and Victoria. However, the comparisons of monthly recharge time series in the six Tomago sites show that there is a large difference between the 0.05o spatially averaged recharge estimates from AWRA and the point field estimates. This is to be expected as for all the six Tomago sites, the groundwater table is within the top two meters and AWRA estimated recharge is defined as the quantity of water leaving at the bottom of the 6 m soil profile. In addition, the spatial variability in point recharge estimates within a 0.05° grid cell for the field recharge estimates can partly account for the differences in the recharge values. Overall, the groundwater recharge assessment undertaken in this study provides confidence in the spatial and temporal trends of the AWRA recharge estimates at 0.05o grids across the continent when compared to the major drivers (e.g., rainfall, land use and soil type) of recharge.

[发布日期] 2015-09-30 [发布机构] CSIRO

[学科分类] 地球科学(综合)