Climatic influences on dryland salinity in central west New South Wales, Australia

Climate influences the incidence of dryland salinity through variations in moisture, as indicated by rainfall, evapotranspiration and drought affecting salinity extent. Climatic influences were examined in relation to dryland salinity in a farming district in central west New South Wales, Australia. Salinity extent was measured at twelve sites using aerial photographs taken at 14 intervals between 1958 and 2004. Results showed that the area of salinity increased over the study period, and increased substantially after 1991. Cumulative patterns of rainfall and moisture surplus influenced salinity more than actual rainfall and surplus amounts over various preceding timeframes. Rainfall was correlated to total saline area over the whole study period (1958-2004) whereas soil moisture surplus and deficit were not. However, moisture surplus was more consistently linked with salinity than was moisture deficit over specific time periods, indicating that an oversupply of water had a stronger influence on salinity than a lack of water. Nevertheless, the severe drought of the early 1980s probably resulted in the rapid expansion of salinity between 1991 and 1996. The time lag between the drought and a salinity response was probably due to preceding and subsequent climate conditions as well as conditions during the drought.