Characterizing streamflow variability: distributions, trends, and ecological impacts
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 ... read morestreamflow 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
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