Groundwater drawdown from mine dewatering in the Pilbara has the potential to impact on coolibah (Eucalyptus victrix) woodlands within and off mining leases. Astron conducted a monitoring program on behalf of a client for coolibah woodland off-lease in a conservation estate adjacent to a mine pit. The program combined traditional survey methods with instrumentation designed to automatically log tree growth and water use.
Growth of coolibah and mulga (Acacia aneura) was automatically recorded using logging dendrometers. These instruments measure fine-scale fluctuations in stem diameter.
Tree water use was measured from “sap flow” in the stem using the Heat Ratio method. Sap flow requires the installation of solar powered, automated logging equipment as well as probes and sensors. Astron’s Dr Tim Bleby, an internationally recognised expert in the sap flow method, oversaw the installation and analysis of sap flow data.
Quarterly monitoring surveys were conducted to maintain and download instruments as well as record additional data. Tree water status at predawn and midday was measured using the pressure chamber technique, projected foliar cover was measured using digital canopy photography and rapid assessments of a large sample of trees were made by experienced observers using visual methods.
Data analysis using control charts and standard statistical tests indicated no impacts to the woodland from dewatering.
The project demonstrated Astron’s technical expertise and capacity to conduct monitoring programs safely and sensitively in high value conservation areas.