Effect of river regulation and rainfall variation on functional streamflow patterns
Abstract
Operation of dams has severely affected floodplains and wetlands worldwide by large scale alteration of streamflow patterns. Anthropocentric Environmental flow, which is widely applied to protect affected river reaches, does not consider floodplains requirement of variable streamflow pulses. This study aimed to assess long-term impact of river regulation and rainfall variation on functional streamflow patterns of Goulburn river in South East Australia. In this study, minimum water requirement of floodplains has been identified as 'functional streamflow' which maintains river-floodplain connectivity through unpredictable flood pulses and drives key functional processes in the floodplains. Long-term trends of annual streamflow and rainfall were analysed using Mann-Kendall nonparametric test and Sen's slope method, Pettit's test was used to determine change point in the rainfall and streamflow time series, and double mass curve technique was used to determine contribution of river regulation and rainfall variation in change in streamflow of Goulburn river. Flow duration curves for mean daily discharge were also developed to determine percent exceedance of functional streamflow during post-regulation period. Results showed significant (at 95% confidence) decline in trends of streamflow during 1884-2018. Overall streamflow of the Goulburn river decreased by 59.82% in post-regulation (1957-2018) as compared to pre-regulation period (1884-1956). Rainfall variation contributed less than 14% and river regulation contributed over 86% to this decrease. As a result, patterns of functional streamflow have changed significantly from upstream to downstream of the river. Functional streamflow in the Goulburn river in post-regulation period exceeded less than 15% however, flows of smaller magnitude exceeded more than 85%. This increased the time span between occurrence of two consecutive flood events of magnitude equal to or higher than functional streamflow. This has very severe implications for health of the Goulburn floodplains and biodiversity of the region.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H33Q2263P
- Keywords:
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- 1804 Catchment;
- HYDROLOGY;
- 1808 Dams;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY;
- 1880 Water management;
- HYDROLOGY