Drought Resilient Pasture Landscapes - Water Quality Drought Resilient Pasture Landscapes - Water Quality

A core element of the Drought Resilient Pasture Landscapes project (2022-2024) was a coaching program to develop producers’ skills and knowledge in: pasture assessment, setting herbage mass targets to maximise pasture productivity and the health of agricultural ecosystems, feed budgeting, and using climate forecasts in the feed budgeting process. These practices have impact at the regional scale of pasture landscapes and complement other considerations such as soil type, waterway buffer width, vegetation, and design that operate at the local scale.

This study was conducted to assess water quality in a number of upland river systems, with catchments dependent on regionally practiced pasture and grazing management. The aim was to improve the knowledge of land managers of waterway health and to understand the connections between pasture management and waterway health. This study was a part of the Drought Resilient Pasture Landscapes (DRPL) project, that received funding from the Australian Government’s Future Drought Fund.

Overall, sites were enriched in total nitrogen and total phosphorus, low in sediment load, and experienced periods of high water temperature and low oxygen saturation. While the amount of bioavailable nutrients was generally low at most sites, the pool of potential nutrient availability was high, suggesting a legacy of lingering nutrient addition. Careful management of phosphatic and nitrogenous fertiliser applications also remains an important component for the health of waterways so as to not further add to the existing nutrient load. With the exception of a few outlier points (and the upstream Apsley River site (APSR2) with a known source of upstream nutrient input), sites were similar to each other. Current land use practices will have an impact on water quality and nutrient loads, but historic land use has a long-lasting legacy effect. For example, the periods of high water temperature and low oxygen saturation are likely a legacy from the large-scale removal of vegetation that has removed overstory plant communities from providing shade to water surfaces. The low level of sediment load observed at all sites is suggestive of good ground cover and adequate level of herbage mass, which combine to reduce rainfall runoff and soil erosion and loss.

Restoring and protecting riparian vegetation and good management of pasture landscapes improves river health, and increases river resilience. Riparian vegetation and pastures with good ground cover and adequate herbage mass reduce erosion, and minimise and trap sediment and nutrients from land run-off, limiting the amount of new pollutants entering the river. Riparian vegetation also significantly reduces summer water temperatures compared to streams that have no shading. The most important step in restoring riparian vegetation is preventing further vegetation loss or damage to restoration efforts by controlling stock access as appropriate.