Oral Presentation Australasian Groundwater Conference 2017

Sustainable management of the Gascoyne River alluvial aquifer through a period of climate variability (#30)

Lazarus Leonhard 1 , Troy Sinclair 1 , Craig Bowman 1
  1. Department of Water Western Australia, Perth, WA, Australia

The sustainable management of the Gascoyne River alluvial aquifer is essential to maintain horticultural production from Carnarvon, Western Australian. Carnarvon is a major horticultural area with a mild climate and a supply of fresh water within the alluvial aquifer. The average Carnarvon rainfall is about 200 mm/yr with horticulture reliant upon irrigated water obtained from the Gascoyne River alluvial aquifer. The Gascoyne River is an ephemeral river that is predominately dry with an extensive fresh water alluvial aquifer recharged during sporadic and infrequent river flow events. Irrigation demand from the alluvial aquifer is about 12 GL/year with requirement for high quality water of less than 455 mg/L of total dissolved solids [TDS]. It is estimated that the banana crop suffers a 30 % decline in production as groundwater salinity increases from 455 to 770 mg/L TDS. Government intervention to limit abstraction and reduce groundwater salinisation occurred in the 1960’s as a consequence of significant degradation in groundwater quality. Current groundwater management is based upon the measurement of groundwater salinity and level that is used to estimate aquifer storage and restrict the production of groundwater with salinity greater than 1000 mg/L TDS. This process utilises a range of tools that include a groundwater storage volume calculator, groundwater salinity contouring and groundwater models. The sustainable management of the alluvial aquifer has become more complex with changes in river flow cycles that have coincided with increased climate variability since the mid – 1970’s. The groundwater model has been revised on a regular basis to provide groundwater storage and quality predictions. Groundwater management issues are an increasing priority due to expansion of the horticultural area with increasing demand, changes in crops and land tenure and increasing climatic variability combined with State provisions to recoup unused groundwater licences and implementation of groundwater entitlement trading.

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