Department of Civil and Environmental Engineering, University of Maine, Orono, ME 04469-5711, USA.
Environ Monit Assess. 2010 Dec;171(1-4):47-58. doi: 10.1007/s10661-010-1525-1. Epub 2010 Jun 25.
Seasonal variations in streamflow and the associated hydrologic extremes impart significant temporal structure to watershed-scale chemical fluxes. Consequently, a careful characterization of the episodic-to-seasonal and longer-term streamflow variations is a first step toward developing a comprehensive view of the temporal dynamics of watershed processes in a changing climate. Here we analyze a nearly two-decade-long streamflow record for the East Bear subwatershed within the Bear Brook Watershed in Maine (BBWM) (USA) to understand the envelope of streamflow variability by season, with a particular focus on the high flow events that have a disproportionately large impact on the biogeochemical processes and fluxes. Interannual and longer-term variations in a number of derived statistical metrics of hydrologic variability are examined. Our analysis shows substantial interannual and longer-term variability in seasonal flow volumes and peak flows. Furthermore, a long, unimpaired streamflow record for the Narraguagus River (a proximate watershed to the BBWM) is examined with a view to understand the relative coherence in hydrologic variability, as well as quantifying the decadal and longer-term hydrologic variations in this region. We find that the streamflow variability in the two watersheds shows similarity in all seasons. A moving window analysis to assess the changing flood potential over time indicates upward trends in the recent decades. Spring season (March-May) flood estimates show a near-monotonic trend over the 1949-2008 record. Finally, empirical relationships between streamflow and large-scale atmospheric circulation patterns highlight the regional and global climatic drivers of hydrologic extremes in this region, including impacts from remnants of Atlantic hurricanes.
季节性的河川流量变化以及相关的水文极端事件，为流域尺度的化学物质通量赋予了显著的时间结构。因此，仔细描述间歇性到季节性和更长时间尺度的河川流量变化，是了解气候变化下流域过程时间动态的第一步。本研究以美国缅因州 Bear Brook 流域（BBWM）中的 East Bear 次流域近 20 年的河川流量记录为分析对象，了解河川流量变化的季节性范围，特别关注对生物地球化学过程和通量有不成比例影响的高流量事件。本研究还研究了一些水文变异性派生统计指标的多年际和长期变化。研究结果表明，季节性流量和峰值流量存在显著的多年际和长期变化。此外，还对 Narraguagus 河（BBWM 的临近流域）的长期、未受干扰的河川流量记录进行了分析，以了解水文变异性的相对一致性，并量化该地区的年代际和长期水文变化。研究发现，两个流域的河川流量变化在所有季节都具有相似性。移动窗口分析评估随时间变化的洪水潜在变化表明，近几十年来有上升趋势。春季（三月至五月）洪水估计在 1949-2008 年的记录中呈现出近单调的趋势。最后，河川流量与大尺度大气环流模式之间的经验关系强调了该地区水文极端事件的区域和全球气候驱动因素，包括大西洋飓风残留的影响。
