Nonstationarity of low flows and their timing in the eastern United States
The analysis of the spatial and temporal patterns of low flows as well as their generation mechanisms over large geographic regions can provide valuable insights and understanding for climate change impacts, regional frequency analysis, risk assessment of extreme events, and decision-making regardin...
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doaj-3141da416a1341e1976fc213f8834d062020-11-24T22:41:53ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382016-02-0120263364910.5194/hess-20-633-2016Nonstationarity of low flows and their timing in the eastern United StatesS. Sadri0J. Kam1J. Sheffield2Princeton University, Princeton, NJ, USAPrinceton University, Princeton, NJ, USAPrinceton University, Princeton, NJ, USAThe analysis of the spatial and temporal patterns of low flows as well as their generation mechanisms over large geographic regions can provide valuable insights and understanding for climate change impacts, regional frequency analysis, risk assessment of extreme events, and decision-making regarding allowable withdrawals. The goal of this paper is to examine nonstationarity in low flow generation across the eastern US and explore the potential anthropogenic influences or climate drivers. We use nonparametric tests to identify abrupt and gradual changes in time series of low flows and their timing for 508 USGS streamflow gauging sites in the eastern US with more than 50 years of daily data, to systematically distinguish the effects of human intervention from those of climate variability. A time series decomposition algorithm was applied to 1-day, 7-day, 30-day, and 90-day annual low flow time series that combines the Box–Ljung test for detection of autocorrelation, the Pettitt test for abrupt step changes and the Mann–Kendall test for monotonic trends. Examination of the USGS notes for each site showed that many of the sites with step changes and around half of the sites with an increasing trend have been documented as having some kind of regulation. Sites with decreasing or no trend are less likely to have documented influences on flows. Overall, a general pattern of increasing low flows in the northeast and decreasing low flows in the southeast is evident over a common time period (1951–2005), even when discarding sites with significant autocorrelation, documented regulation or other human impacts. The north–south pattern of trends is consistent with changes in antecedent precipitation. The main exception is along the mid-Atlantic coastal aquifer system from eastern Virginia northwards, where low flows have decreased despite increasing precipitation, and suggests that declining groundwater levels due to pumping may have contributed to decreased low flows. For most sites, the majority of low flows occur in one season in the late summer to fall, as driven by the lower precipitation and higher evaporative demand in this season, but this is complicated in many regions because of the presence of a secondary low flow season in the winter for sites in the extreme northeast and in the spring for sites in Florida. Trends in low flow timing are generally undetectable, although abrupt step changes appear to be associated with regulation.http://www.hydrol-earth-syst-sci.net/20/633/2016/hess-20-633-2016.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
S. Sadri J. Kam J. Sheffield |
spellingShingle |
S. Sadri J. Kam J. Sheffield Nonstationarity of low flows and their timing in the eastern United States Hydrology and Earth System Sciences |
author_facet |
S. Sadri J. Kam J. Sheffield |
author_sort |
S. Sadri |
title |
Nonstationarity of low flows and their timing in the eastern United States |
title_short |
Nonstationarity of low flows and their timing in the eastern United States |
title_full |
Nonstationarity of low flows and their timing in the eastern United States |
title_fullStr |
Nonstationarity of low flows and their timing in the eastern United States |
title_full_unstemmed |
Nonstationarity of low flows and their timing in the eastern United States |
title_sort |
nonstationarity of low flows and their timing in the eastern united states |
publisher |
Copernicus Publications |
series |
Hydrology and Earth System Sciences |
issn |
1027-5606 1607-7938 |
publishDate |
2016-02-01 |
description |
The analysis of the spatial and temporal patterns of low flows as well as
their generation mechanisms over large geographic regions can provide
valuable insights and understanding for climate change impacts, regional
frequency analysis, risk assessment of extreme events, and decision-making
regarding allowable withdrawals. The goal of this paper is to examine
nonstationarity in low flow generation across the eastern US and explore the
potential anthropogenic influences or climate drivers. We use nonparametric
tests to identify abrupt and gradual changes in time series of low flows and
their timing for 508 USGS streamflow gauging sites in the eastern US with
more than 50 years of daily data, to systematically distinguish the effects
of human intervention from those of climate variability. A time series
decomposition algorithm was applied to 1-day, 7-day, 30-day, and 90-day
annual low flow time series that combines the Box–Ljung test for detection
of autocorrelation, the Pettitt test for abrupt step changes and the
Mann–Kendall test for monotonic trends. Examination of the USGS notes for
each site showed that many of the sites with step changes and around half of
the sites with an increasing trend have been documented as having some kind
of regulation. Sites with decreasing or no trend are less likely to have
documented influences on flows. Overall, a general pattern of increasing low
flows in the northeast and decreasing low flows in the southeast is evident
over a common time period (1951–2005), even when discarding sites with
significant autocorrelation, documented regulation or other human impacts.
The north–south pattern of trends is consistent with changes in antecedent
precipitation. The main exception is along the mid-Atlantic coastal aquifer
system from eastern Virginia northwards, where low flows have decreased
despite increasing precipitation, and suggests that declining groundwater
levels due to pumping may have contributed to decreased low flows. For most
sites, the majority of low flows occur in one season in the late summer to
fall, as driven by the lower precipitation and higher evaporative demand in
this season, but this is complicated in many regions because of the presence
of a secondary low flow season in the winter for sites in the extreme
northeast and in the spring for sites in Florida. Trends in low flow timing
are generally undetectable, although abrupt step changes appear to be
associated with regulation. |
url |
http://www.hydrol-earth-syst-sci.net/20/633/2016/hess-20-633-2016.pdf |
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