GC41D-0595 Low Flows over the Eastern United States (1962-2011): Variability, Trends, and Attributions Background: Low Flow Hydrology

• Main Authors: Jonghun Kam, [e-mail] Justin Sheffield
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Pacific; North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1046.1925; http://hydrology.princeton.edu/%7Ejkam/index.files/AGU_2014_KamJ.pdf

Abstract We examined trends and variability in low flows over the eastern U.S. (S. Carolina to Maine) and their attribution in a changing climate. We selected 149 out of 4878 USGS stations over the eastern U.S., taking into account data availability and minimal direct management. Annual 7-day low flows (Q7) were computed from the series of daily stream flow records for 1962-2011 and compared to an antecedent precipitation (AP) index calculated over the corresponding basin for each station. A north-south increasing-decreasing pattern in low flow trends was found that is associated with trends in AP. The exception is in the southern part of the domain where increasing trends in AP may have been offset by water withdrawals and increasing potential evapotranspiration (PET) as driven by increasing temperature and vapor pressure deficit. Teleconnections between detrended Q7 and nine atmospheric and oceanic climate indices indicate that the North Atlantic Oscillation (NAO) and Pacific North America (PNA) pattern show statistically significant correlations for Q7 at one and two month lead time, respectively. Our findings suggest that the risk of future hydrological droughts is increased during a strong negative phase of the NAO and positive phase of the PNA during the summer, and may be further enhanced with temperature driven increases in PET. Conclusions 1) A dipole pattern of increasing and decreasing (north-south) trends in Q7 low flows exists. 2) Decreasing trends in Q7 over the Mid-ATL region and the southern part of the SE region including North and South Carolina and Virginia. 3) The decreasing trends are possibly linked to increasing trends in PET driven by warming temperature. 4) NAO (-) and PNA (+) : A favorable condition for drought over the Mid-ATL and SE regions.