Freshwater is a scarce resource, and maintaining water quality is of great importance in dryland Australia. How water quality is affected by the dry climate and socio-economic influences in Australia remains widely unknown. Here, we find that agriculture activity dominates reactive nitrogen (Nr) emissions to water bodies. Such emissions not only contribute to deteriorating water quality in Southeastern Australia but also harm marine ecosystems, including the Great Barrier Reef, a World Natural Heritage site. A dry and warm climate reduces the share of Nr emitted directly to water bodies; however, it increases the Nr concentration in surface water due to reduced water volume, leading to a 3-fold higher water Nr concentration compared to major rivers globally, e.g., in the US or China. Business-as-usual socioeconomic development would increase the total Nr emitted to surface water by at least 43% by 2050, while effective mitigation measures could reduce N runoff by about 27%. Advanced agricultural management strategies should be considered to reduce future environmental pressures due to N runoff in Australia.
Keywords: climate effects; nitrogen cycle; policy; scenario prediction; surface water pollution.