Linking water quality trends with land use intensification in dairy farming catchments

SummaryAgriculture, particularly pastoral based dairying, has intensified significantly in the past two decades. There are mounting concerns that this intensification could be linked to declining environmental quality. This paper analyses changes in water quality in three catchments in south-west Victoria, Australia, where the dominant land use has been dairying for the past 21 years and where the intensity of milk production has increased, driven by changes in farming systems and imports of nitrogen (N) and phosphorus (P) in various forms. We aimed to investigate if water quality has changed over that period and if such changes were related to the intensity of land use at the catchment scale. Three adjoining catchments were investigated which are different in terms of hydrology, biochemistry and land use proportions. Statistical analysis of continuous datasets showed that concentrations of N and P changed over the 21 year period. There were notable links between the intensification of milk production and increasing concentrations of N and P in streams from 1990 to 2000. The influence varied between catchments possibly due to hydrological differences that in turn influence biogeochemistry. From 2000 to 2011, there is some evidence this link may be starting to become decoupled due to various changes in farming systems, although it is difficult to specify which changes have had the greatest effect. The outcome of the close links between production intensification and water quality is that without fundamental changes to the farming systems, or without physical changes implemented in the catchment such as more effective riparian buffers or treatment wetlands, increases in agricultural intensity may lead to further degradation of water quality. Through this study the importance of investigating multiple water quality parameters and land use datasets to understand catchment functioning has been highlighted.

► Water quality in three catchments used for dairy farming was investigated.
► Land use remained constant but changes were observed in select water quality trends.
► Links between of milk production and N and P concentrations from 1990 to 2000.
► From 2000 to 2010, links may have decoupled to due changes in farming systems.