Evaluation of the effect of climate variability on long term trends in groundwater tables in south-western agricultural areas in WA.

Project Aims

The aim of this undergraduate research project is to evaluate surface water and groundwater interactions and determine the impacts of climate variability on groundwater systems in the agricultural areas of the south west of WA. The project will examine long-term groundwater trends utilising, bore, rainfall and runoff data for three catchments in the WA agricultural region. These catchments will be compared to other sites within the region to determine any correlations between site characteristics, climate variations and trends in surface water and groundwater interactions. In addition, the role of land management practices for these catchments will be examined to identify any causal relationships between groundwater rise, secondary salinity and land management practices.

The primary sites for the project are catchments in Perenjori, Wallitin Creek and Cuballing, located in the Northern, Central and South-Western Agricultural regions, respectively. These sites have been monitored by the Department of Agriculture for twenty years for groundwater levels and continuous rainfall data. This information will be evaluated using hydrological time series analysis through the data archive program Hydstra. It is expected that the underlying geology at the sites will be identified using geological logs from bores installed at the sites to determine the attributes of the aquifers identified (i.e. semi-confined, confined) and their geology on groundwater trends.

Hydrogeology

This project will attempt to quantify the impacts of climate variability on groundwater systems in semi-arid and ephemeral environments. Specifically the relationships between what percentage of rainfall contributes to surface water runoff and aquifer recharge. This is particularly important in WA, where the water supply is highly dependent on groundwater resources and resource condition in low lying areas in the wheatbelt is impacted by secondary salinity caused by rising groundwater tables.

Previous research has shown that groundwater tables are rising (Nulsen, 1998; Lewis & McConnell 1998; Hatton & Ruprecht 2001;) with significant impacts on agricultural productivity forecast for the future. Recent work has suggested that these trends are being reversed (George et al 2004; Bennett and George 2008). It is expected that this proposed research will provide hydrogeologists and resource managers with an improved understanding of the functionality of regional and localised aquifers, and their impact on waterlogging in valley floors that influence secondary salinity development in the wheatbelt.

References

Bennet D and George R 2008 ‘Long term monitoring of groundwater levels at 24 sites in Western Australia shows that integrated farm forestry systems have little impact on salinity’ in International Salinity Forum 2008.

George R, Clarke J and English P 2008, ‘Modern and palaeogeographic trends in the salinisation of the Western Australian wheatbelt: a review,’ Australian Journal of Soil Research, vol.46, pp. 751-767.

Hatton T and Ruprecht J 2001, ‘Watching the Rivers Flow: Hydrology of the Wheatbelt,’ in Dealing with Salinity in Wheatbelt Valleys: Processes, Prospects and Practical Options.

Lewis MF and McConnell CE 1998, Observations on Groundwater Recharge in the Westdale Catchment, Resource Management Technical Report 180.

Nulsen, B (ed.) 1998, Groundwater Trends in the Agricultural Area of Western Australia, Resource Management Technical Report 173.