Science, Technology and Engineering

Environmental Geoscience

Postgraduate Projects

Modeling hydrograph response to climate and land use changes and relating the impacts to groundwater salinisation and lake level/salinity in western Victoria

Yohannes Yihdego

Supervisor: Dr John Webb

This project aims to model the seasonal and decadal fluctuations in water table across the basalt plains in the southern Glenelg Hopkins catchment in terms of climate and land use. Two manifestations of the water table will be studied: lake heights and bore levels. In addition, the salinity fluctuations in lake waters will be modelled. Stream modelling, Lake modelling and Groundwater modelling will be carried out. Using Lake modelling It will be possible to predict the changes in lake level and salinity for any of these lakes for any postulated climatic regime, e.g. the amount of rain needed to restore them to their pre-drought (pre-1997) condition.

The aim is to develop a model that quantifies the relative input of climate and land use change to the fluctuations in water table and lake level through out the basalt plains part of the catchment. The modelling can then be used to predict how much the water tables will change as a result of variation in the amount and distribution of future rainfall, in conjunction with land use changes like revegetation or changing from grazing to cropping, and thus helping to set realistic resources condition targets.

The agricultural productivity, surface water quality and tourism potential of the Glenelg-Hopkins catchment in western Victoria, is threatened by increasing salinity problems.Specifically,productivity of much of the basalt agriculture land is threatened by salinization.Rising water tables have resulted in areas of saline scalding, and caused highly saline groundwater to leak in to the surface streams and lakes. The basalt plains area is a priority area for treatment under the Glenelg Hopkins Salinity plan 2005-2008.

This project will provide a valuable series of models that will provide useful information to the Glenelg-Hopkins CMA, and assist with management of the water resources of the region. This project will provide valuable input to the regional action target for water way health and quality, because setting resource condition targets is dependent on accurate knowledge of the relative influence of climate and land use. Water table and lake levels across much of the Glenelg-Hopkins catchment have been declining for at least the last 10-15 years, and this is attributed to the consistently low rainfall for these years, but over the same period of time there has been substantial change in land use, with grazing land replaced by cropping and tree plantations appearing in some areas. It is important to determine the relative effect the climate and land use factors on the water table changes.

The project is supported by the Glenelg-Hopkins Catchment Management Authority.