Mapping and predicting salinity using a geographic information system

This project studies a portion of the Lake Wellington catchment, between the La Trobe and Avon rivers, to the northwest of Lake Wellington. The aim of the study is to investigate the use of a Geographic Information System, in this case ArcView, to map existing and predict possible future occurrence of dryland salinity. In order to achieve the aims of the study four models were developed. The first model involved an assessment of the groundwater table levels to determine recharge and discharge areas within the catchment. The second model evaluated evaporation and rainfall to also help determine their influence on the recharge and discharge processes in the catchment. The third model assessed the physical characteristics of the landscape, specifically, elevation and soil types particularly clay content. The fourth and last model was salinity prediction, which was carried out based on rainfall, evaporation, clay content and the slope as well as existing water tables to determine the areas at risk of salinity. Results obtained show that the eastern part of the catchment has relatively shallow tables as compared to the west, irrespective of the season. This means that the eastern part of the catchment is mainly a discharge area , hence suffers from salinity. The the west on the other hand is predominantly a recharge area, evidenced by deeper water tables. The study also indicates that the east of the catchment, which is also relatively shallow experiences increased amounts of moisture loss through evaporation, and low rainfall levels. The west on the other hand is deeper, experiences lower evaporation and high levels of precipitation. Another finding was that the east and south east is relatively flat compared to the north, and recharge areas have soils with higher clay content compared to the discharge zones. Prediction results however portray a different picture. On average, the entire study area is prone to salinity, with the north and north western parts at medium level salinity risk. The south and south east on the other hand is at a higher risk level as evidenced by slightly shallow tables as compared to the north. Right in the centre of the study area is a high level discharge area with relatively shallower water tables, and at high risk of salinity. There are also pockets of high level recharge areas in the centre of the study area. These are not likely to suffer from salinity as they are comparatively deep