Analysis of Streamflow Trend in the Susquehanna River Basin, USA - Hydrologic Time Series Analysis: Theory and Practice - page 179

9
Analysis of Streamflow Trend in the
Susquehanna River Basin, USA
9.1 Introduction
Streamflow statistics are extensively employed for the management and
development of water resources. The magnitude and frequency of streamflows
in the Susquehanna River Basin (SRB) are often used by the Susquehanna
River Basin Commission (SRBC) and other agencies for the purposes of
water resources planning and management (SRBC, 2006). For example, a
wide range of streamflow statistics are used for consumptive water use
mitigation, reservoir operation, and minimum release management. Water
resources engineers and managers often implicitly assume that streamflow
series are stationary over time when using streamflow data and statistics
(SRBC, 2006; Zhang and Kroll, 2007a,b; Milly et al., 2008). This assumption
may not be valid if the watershed under consideration is sensitive to human
disturbance and/or climate change. More generally, climate variability, and
change in population, land use and water use are implicated in the non-
stationarity of streamflow series (Koutsoyiannis et al., 2009; Lins and Stakhiv,
1998; Milly et al., 2008). In a review of its consumptive use mitigation strategy,
the SRBC examined the frequency and duration of consumptive use
compensation releases from reservoirs located in the upper reaches of the
SRB. It was evident that the number and frequency of 7-day-10-year low flow
(Q 7,10 ) events had dropped substantially since around 1970. This suggests that
the assumption of stationarity in the basin might be invalid. Therefore, an
investigation of the assumption of streamflow stationarity in the SRB was of
interest.
Invited contribution by Zhenxing Zhang, Robert D. Pody, Andrew D. Dehoff and John
W. Balay - Susquehanna River Basin Commission, 1721 N. Front Street, Harrisburg,
PA, USA.