This data summarises the results of a spatial analysis to identify significant tributary junctions in rivers, across the NSW Murray-Darling Basin, where inflows from unregulated or less regulated tributaries join heavily regulated rivers. Tributary junctions were characterized in terms of the relative change in the ‘Degree of Regulation’ (DoR) at individual tributary junctions. DoR was calculated as the ratio of the storage capacity of all upstream reservoirs relative to the mean annual runoff. Furthermore, This spatial analysis identifies potential tributary hotspots across the NSW Murray-Darling Basin (MBD).

Rivers often experience major discontinuities in ecological function due to dams, whereby the timing and volume of flow and water chemistry can be significantly altered from upstream to downstream of the dam, impacting ecosystem productivity and aquatic food webs. Tributary inflows from such unregulated catchments can play an important role in mitigating changes in water chemistry below large dams, thereby overcoming the so-called serial discontinuity effect, which describes the impacts of large dams on longitudinal gradients in water chemistry. Because tributary inflows can be rich in nutrients and dissolved carbon, they can lead to ‘priming’ effects, in which biogeochemical processes and ecosystem productivity are enhanced below confluences with more heavily regulated rivers. Yet, there have been few attempts to identify potential priority tributaries that may play a larger role in driving biochemistry and ecosystem function below dams. This spatial analysis identifies significant tributary junctions in rivers, across the NSW Murray-Darling Basin, where inflows from unregulated or less regulated tributaries join heavily regulated rivers.

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