The Influence of Water Scarcity and Drought on the Lindis River, Central Otago.

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

The Influence of Water Scarcity and Drought on the Lindis River, Central Otago.

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

Streamflow droughts aggravated by human activities despite management

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems

Streamflow droughts aggravated by human activities despite management

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems

Streamflow droughts aggravated by human activities despite management

Human activities both aggravate and alleviate streamflow drought. Here we show that aggravation is dominant in contrasting cases around the world analysed with a consistent methodology. Our 28 cases included different combinations of human-water interactions. We found that water abstraction aggravated all drought characteristics, with increases of 20%-305% in total time in drought found across the case studies, and increases in total deficit of up to almost 3000%. Water transfers reduced drought time and deficit by up to 97%. In cases with both abstraction and water transfers into the catchment or augmenting streamflow from groundwater, the water inputs could not compensate for the aggravation of droughts due to abstraction and only shift the effects in space or time. Reservoir releases for downstream water use alleviated droughts in the dry season, but also led to deficits in the wet season by changing flow seasonality. This led to minor changes in average drought duration (-26 to +38%) and moderate changes in average drought deficit (-86 to +369%). Land use showed a smaller impact on streamflow drought, also with both increases and decreases observed (-48 to +98%). Sewage return flows and pipe leakage possibly counteracted the effects of increased imperviousness in urban areas; however, untangling the effects of land use change on streamflow drought is challenging. This synthesis of diverse global cases highlights the complexity of the human influence on streamflow drought and the added value of empirical comparative studies. Results indicate both intended and unintended consequences of water management and infrastructure on downstream society and ecosystems