Characterizing streamflow variability: distributions, trends, and ecological impacts
Blum, Annalise.
2017
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Abstract: To manage water resources and prepare for extreme hydrologic events, an understanding of streamflow variability is necessary. Globally, the majority of river basins are ungaged, a challenge which is compounded by on-going anthropogenic interference with the natural flow regime of nearly all rivers. Statistical models are a powerful tool for capitalizing on available data to predict strea... read moremflow at gaged and ungaged sites and to determine the ecological implications of streamflow variability. To improve understanding of daily streamflow across the United States (US), the first chapter of this dissertation identifies probability distributions which can approximate daily streamflow at nearly 400 minimally-impacted stream gages. Differences in distributional fit across physiographic regions were identified. Across the majority of the US, the four-parameter kappa distribution was found to provide a very good representation of the distribution of daily streamflow. The second chapter focuses on better accounting for streamflow variability over time. In the context of possible trends, simple data selection methods are compared to update estimators of the most common low streamflow statistic, 7Q10, the annual minimum seven-day streamflow which is exceeded in nine out of ten years on average. Selecting only the most recent thirty years of flow records from a longer record was found to generally to improve accuracy of 7Q10 estimators, particularly for large magnitude trends. Finally, predictions of future streamflow at ungaged locations are needed to anticipate and mitigate the ecological impacts of changes in streamflow extremes. Using predicted streamflow, the third chapter identifies the effect of seasonal streamflow extremes on brook trout young-of-the-year (YOY) abundance in Shenandoah National Park. High peak winter streamflow and insufficient fall streamflow were strongly associated with reduced next summer YOY abundance. Forecasted increases in winter streamflow, as well as temperature year-round, are expected to have a negative effect on future brook trout populations in this region.
Thesis (Ph.D.)--Tufts University, 2017.
Submitted to the Dept. of Civil Engineering.
Advisor: Richard Vogel.
Committee: Stacey Archfield, Benjamin Letcher, and Charles Kroll.
Keywords: Hydrologic sciences, and Ecology.read less - ID:
- 7m01bz11n
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