Identifying spatial and temporal patterns in the hydrological character of the Condamine-Ballone River, Australia, using multivariate statistics

Many environmental flow approaches calculate hydrological indicators on an annual or daily basis and do not consider the multiple scales of a rivers' hydrological character. However, hydrologic processes operate within a temporal and spatial dimension, in accordance with multidimensional and hierarchical views of river systems. This study investigates spatial and temporal patterns of the hydrological character of a large river system, and examines the impact of water-resource development on these patterns. Over 300 regime, history and pulse-scale flow variables have been calculated from simulated discharge data representing ‘reference’ and ‘current’ water-resource development scenarios. Multivariate statistical analyses are used to identify measurement nodes with similar hydrological character and to determine the association between different temporal scale flow variables and groups of nodes. Six spatial hydrological zones are identified in the Condamine–Balonne River, Australia. These hydrological zones are found to have become homogenized with water-resource development. Different temporal scales of flow variables are related to the different hydrological zones, and to water-resource development scenarios. Thus, the temporal dimension of hydrological character is embedded within a spatial dimension of river zonation. Both dimensions should be considered in a hierarchical context, and environmental flow restoration targets may need to be set for each dimension of a river system