Groundwater modelling report – Lower Murrumbidgee. CSIRO: Water for a Healthy Country National Research Flagship

[摘要] A numerical groundwater model was used to assess the long-term impact of preliminary extraction limits for groundwater pumping from the Lower Murrumbidgee aquifers. Predictive models were developed and run for eight different fifty-year scenarios and the results assessed against four criteria aimed at determining the sustainability of the particular scenario. These criteria are:•Criterion 1. Stabilisation of groundwater levels (productive base and key environmental outcome requirement).To meet this sustainability criterion groundwater levels must have stabilised or be rising at the completion of the scenario model run (i.e. after 43 years of extraction at the defined preliminary extraction limit) at the RCI (Resource Condition Indicator) sites.•Criterion 2. Ability to maintain volume of extraction (productive base requirement).The groundwater extraction rates are automatically reduced in groundwater models if a model cell from which groundwater is being extracted dries out due to excessive drawdown.To meet this criteria the model must maintain pumping at the required rate for the duration of the scenario model run. •Criterion 3. Prevention of dewatering of confined aquifers (productive base and key environmental outcome requirement).To meet this criterion the predicted groundwater levels at all RCI sites must remain above the top of a confined aquifer.•Criterion 4. Impact on surface-water streamflows (key environmental assets and key ecosystem functions requirement).This criterion mandates that the sustainable extraction limit must be equal to or less than the current level of groundwater extraction.In this regard the current level of groundwater extraction is defined as the average of the last five years of groundwater extraction.Current levels of groundwater extraction (318 GL/year) are being reduced to meet the New South Wales Water Sharing Plan target of 294.5 GL/year – including an allowance for stock and domestic water supplies. Model results indicate that scenarios that include annual extraction of 294.5, 280 and 327 GL/year from 2017 appear to be sustainable when assessed against the four sustainability criteria used in this study. On this basis a preliminary extraction limit of 327 GL/year is proposed factored down to 295 GL/year to account for model uncertainty.

[发布机构] CSIRO

[学科分类] 地球科学(综合)