Event-scale hydrologic connectivity of the Murray-Darling Basin

[摘要] This report presents the findings of a modelling study examining event scale hydrologic connectivity across the Murray Darling Basin.River flow in the Murray-Darling Basin is heavily influenced by hydrologic "losses'' such as infiltration of river flow to groundwater, or evapotranspiration from river channels, floodplains and wetlands, such that only some proportion of upstream flow reaches downstream locations. Hydrologic connectivity here is examined using a modelling strategy that examines the proportion of upstream flood pulse volume that reaches selected downstream locations, with this proportion referred to as "flow efficiency''. The study utilises the Integrated River System Modelling Framework which links a series of regional river system models into a single model for the Murray-Darling Basin.For a selection of headwater reaches of the Basin, flood pulses with recurrence intervals of 1, 2, 5, 10, 20, 50, and 100 years have been examined.This focus on event-scale responses represents and advance on previous assessments that utilised mean annual values.Consistent with previous research, rivers of the northern Basin (ie. those rivers flowing to the Barwon-Darling River) have in general relatively low flow efficiency values (with regards to flow to the lower Murray River).Typically only 20 to 40% of flood pulse volume from this region reaches the lower Murray River.This is roughly half the proportion from the headwater reaches of the "southern connected system'' (Murrumbidgee, Upper Murray, Goulburn Rivers).However there is often considerable inter-annual variability in flow efficiency values arising from the interaction of tributary flows with the loss characteristics represented in the various river system models.The methodology adopted here has allowed for statistical models that represent the inter-annual variability of flow efficiency values to be developed.These models serve two purposes.Firstly the models can highlight "emergent properties'' concerning the relationships between river flow and flow efficiency values which otherwise remain hidden within the regional river system models.Secondly, the fitted models allow for prediction of flow efficiency values, given a prevailing set of hydrologic conditions, if so desired.Consequently the models may be of value in planning environmental watering actions where rapid assessment of downstream volumetric transfer of upstream flood pulses is desired.

[发布日期] 2012-07-04 [发布机构] CSIRO

[学科分类] 地球科学(综合)