US Geological Survey Charleston, WV

1. US Geological SurveyCharleston, WV Water quantity assessments and trends in low flow October 29, 2004

2. Definition Climatic year

3. Definition Hydrologic-based frequency (7Q10)

4. Definition Biologic-based frequency (4B3)

5. Definition Harmonic daily-mean flow (harmonic mean)

6. Selected Annual Flow Statisticsfor the Greenbrier River at Alderson (station number 03183500) for the entire period of record 1B3..���46.8 cfs 1Q10��..47.8 cfs 4B3..���49.5 cfs 7Q10��..52.4 cfs 30Q5���85.7 cfs Harmonic mean��..394 cfs

7. Lins, H.F., and Slack, J.R., 1999, Streamflow trends in the United States; Geophysical Research Letters, v. 26, pp. 227-230. Abstract. Secular trends in streamflow are evaluated for 395 climate-sensitive streamgaging stations in the conterminous United States using the non-parametric Mann-Kendall test. Trends are calculated for selected quantiles of discharge, from the 0th to the 100th percentile, to evaluate differences between low-, medium-, and high-flow regimes during the twentieth century. Two general patterns emerge; trends are most prevalent in the annual minimum (Q0) to median (Q50) flow categories and least prevalent in the annual maximum (Q100) category; and, at all but the highest quantiles, streamflow has increased across broad sections of the United States. Decreases appear only in parts of the Pacific Northwest and the Southeast. Systematic patterns are less apparent in the Q100 flow. Hydrologically, these results indicate that the conterminous U.S. is getting wetter, but less extreme. Lins, H.F., and Slack, J.R., 1999, Streamflow trends in the United States; Geophysical Research Letters, v. 26, pp. 227-230. Abstract. Secular trends in streamflow are evaluated for 395 climate-sensitive streamgaging stations in the conterminous United States using the non-parametric Mann-Kendall test. Trends are calculated for selected quantiles of discharge, from the 0th to the 100th percentile, to evaluate differences between low-, medium-, and high-flow regimes during the twentieth century. Two general patterns emerge; trends are most prevalent in the annual minimum (Q0) to median (Q50) flow categories and least prevalent in the annual maximum (Q100) category; and, at all but the highest quantiles, streamflow has increased across broad sections of the United States. Decreases appear only in parts of the Pacific Northwest and the Southeast. Systematic patterns are less apparent in the Q100 flow. Hydrologically, these results indicate that the conterminous U.S. is getting wetter, but less extreme.

8. Definition Standardized departure (normalize data)

9. McCabe, G.J. and Wolock, D.M., 2002, A step increase in streamflow in the conterminous United States; Geophysical Research Letters, v. 29, no. 24, 2185, doi:1029/200GL015999. Annual minimum, median, and maximum daily streamflow for 400 sites in the conterminous United States (U.S.), measured during 1941 � 1999, were examined to identify the temporal and spatial character of changes in streamflow statistics. Results indicate a noticeable increase in annual minimum and median daily streamflow around 1970, and a less significant mixed pattern of increases and decreases in annual maximum daily streamflow. These changes in annual streamflow statistics primarily occurred in the eastern U.S. In addition, the streamflow increases appear as a step change rather than as a gradual trend and coincide with an increase in precipitation. McCabe, G.J. and Wolock, D.M., 2002, A step increase in streamflow in the conterminous United States; Geophysical Research Letters, v. 29, no. 24, 2185, doi:1029/200GL015999. Annual minimum, median, and maximum daily streamflow for 400 sites in the conterminous United States (U.S.), measured during 1941 � 1999, were examined to identify the temporal and spatial character of changes in streamflow statistics. Results indicate a noticeable increase in annual minimum and median daily streamflow around 1970, and a less significant mixed pattern of increases and decreases in annual maximum daily streamflow. These changes in annual streamflow statistics primarily occurred in the eastern U.S. In addition, the streamflow increases appear as a step change rather than as a gradual trend and coincide with an increase in precipitation.

10. USGS in cooperation with WVDEP Evaluate low-flow trends in WV Quantify variability of selected low-flow statistics Develop a procedure to manage periods of gaging-station records and trends in low flow for estimating low-flows on ungaged streams Compute selected station statistics

15. Regional analysis of standardized departures

17. Summary The value of low-flow statistics are sensitive to the period of record at a station and the climatic changes over that period The sensitivity of low flow statistics to climate change decreases with increasing streamflow Climatic changes affecting low flows have regional characteristics

18. Questions Jeffrey B. Wiley U.S. Geological Survey 11 Dunbar Street Charleston, WV 5301 (304)347-5130 X234 jbwiley@usgs.gov