Abstract
Water scarce situations are a critical issue in water resource management. Water scarcity can be exacerbated by drier than usual conditions (such as drought), and separating the effects of water scarcity and drought can be difficult. This study investigates the relative importance of water scarcity and drought on the availability of water in the Lindis River (Central Otago, New Zealand). The Lindis catchment is a tributary of the Clutha River and frequently becomes disconnected in the summer months. To determine the extent to which these extreme low flows are driven by abstractions versus the naturally dry conditions that occur in summer, a two-step hydrological modelling procedure was employed. First, the HBV-Light hydrological model was developed for the upper Lindis. This model is then applied to the lower Lindis, to provide an indication of what ‘natural’ flow should be in the lower catchment. Comparison of the modelled (natural) river flow record with the observed (anthropogenic + natural) river flow record suggested that summer river flow in the lower Lindis is substantially lower than it would be in the absence of human abstraction. Anomaly analysis indicates that the ‘natural’ Lindis River would not disconnect from the Clutha River from January-March, and would only have rare short disconnection events in December and April, in comparison to their frequent occurrence in reality. As such, the results of this study have the potential to provide vital information for the on-going management of flow in this catchment.