CFE agenda 091117 - Laserfiche WebLink

Browse Search

Climate Change Assessment for Water Resources Region 03 South Atlantic -Gulf Trends in the frequency and severity of droughts in the Southeast U.S. were the subject of studies by Chen et al. (2012) and Cook et al. (2014). In the first study, historical data (1895 — 2007) for the southern USA, including the South Atlantic -Gulf Region, were used to identify trends in drought, as defined by the standard precipitation index (SPI). The SPI is a metric of precipitation only and neglects the impacts of ET on droughts (Chen et al., 2012). The authors were not able to identify significant trends in either the frequency or intensity of droughts in the study region. The second set of authors used tree ring data to assess the frequency and severity of droughts over the past millennium (1000 — 2005), across the U.S. For the southeast region, which includes the South Atlantic -Gulf Region, the authors identified a statistically significant decline in drought frequency (droughts per century) over the past 1,000 years and a general increase in soil moisture, as defined by the Palmer Drought Severity Index (PDSI), over the same period (Figure 2.12). ;, ,R SIN C NW Nw sr Meet* POSI 09,, OR r CAOIN qID Vft yW)q 0OW ,WO f"ft 1,V46 Iroft 11901p 0X% 11i1W u61111N Weir fM" 00h, O 11"K irk rr1010m HIO'i , Figure 2.12. Drought frequency and severity for southeast USA (light green), based on Palmer Drought Severity Index (PDSI), 1000s — 1900s. (Cook et al., 2014). Ivey point: A Indd upward trend in precipitation in the study region, in ter lns of both annual totals and occurrence of stor In events, hers been identified by multiple authors but a clear consensus is lacking. evidence hers also been presented indicating an increase in the year -to- year variability in precipitation. 2.3. Hydrology Studies of trends and non- stationarity in streamflow data collected over the past century have been performed throughout the continental U.S., some of which include the South Atlantic -Gulf Region. In 2013, Xu et al. investigated trends for multiple stream gages in the South Atlantic - Gulf Region. This study used the Model Parameter Estimation Experiment ( MOPEX) data set for the period 1950 — 2000. Additional information on the MOPEX can be found in Duan et al. (2006). Statistically significant negative trends in both annual streamflow and baseflow were identified for two stations in Florida. The vast majority of stations, distributed throughout the HUC, show no significant trend in streamflow in either direction. In contrast to the findings described above, Kalra et al. (2008) found statistically significant negative trends in annual and seasonal streamflow for a large number of stream gages in the South Atlantic -Gulf Region, analyzed in aggregate, for the historical period 1952 — 2001. This study also identified a statistically significant stepwise change occurring in the mid- 1970s, USACE Institute for Water Resources 18 January 9, 2015