SEMINAR: �Eddy covariance fluxes and cosmic rays for soil moisture and recharge monitoring on Gnangara Mound � a novel approach to establishing water and carbon balances in a groundwater recharge area�

An atmospheric flux station has been established 70 km north of Perth, with funding from the Commonwealth Govt through the Terrestrial Ecoscience Research Network (TERN) and CSIRO. The site has been selected for its importance as representative of the recharge area and its ecological value. South-west WA is Australia’s only recognised global biodiversity hotspot, and also the region with the most significant impact of climate change on water resources in the country. These measurements will enable a better calculation of recharge to the groundwater under this ecosystem than previously available, and will monitor how the vegetation is responding to changes in climate and other influences.

The instruments record atmospheric fluxes and exchanges between the surface and atmosphere of water vapour, carbon dioxide, energy and momentum, along with soil moisture and groundwater dynamics. The water vapour flux measurement represents total surface evapotranspiration and is analogous to a stream gauging station measuring river flows from a catchment, integrating all processes that result in evaporation away from the groundwater recharge area. The site is part of the Australia-wide OzFlux network of atmospheric flux stations. It also has a COSMOS (Cosmic ray derived neutrons) soil moisture monitoring system as part of a national network of 11 sites. The COSMOS system provides hourly measurements of inferred soil moisture storage within the shallow soil (to about 80cm at this site). These data will provide the first large scale estimate of the recharge under the woodland; the measurements have a footprint with about 1 km diameter. Coupled with the carbon flux measurements it will enable improved understanding of ecosystem function and water relations under current climate trends of reducing rainfall, increasing temperatures and declining groundwater levels.