HYDROLOGIC VARIABLITY AND CHANGE IN THE NEW ENGLAND REGION, USA

Traditional water resources management aims to ensure the steady and reliable
water supply for human uses and maximize the economic benefits by dampening natural
flow variability. However, such management practices essentially changes the flow
regime in many ways and ecological degradation is one of the obvious consequences of
that. Natural functioning and productivity of the native species require enough water in
the streams and lakes with sufficient quality. Thus, to protect the natural ecosystem
diversity, sustainable water allocation policies have been developed and employed by
many societies around the world. “Chapter 587: In-stream Flow and Lake and Pond
Water Levels” is an excellent example of proactive management and planning within a
water allocation framework in achieving long-term sustainability of water resources in
Maine. Success of this water policy largely depends on using a reasonable guide of
ranges of hydrologic variability that may occur in the future, as well as updating the
policy to reflect changes and trends in water resources from human activities. A primary
context for this work is Maine’s newly established water allocation framework, Chapter
587. The focus of this study is twofold: (a) to analyze a multi-century tree-ring based
record of droughts in Maine and a framework to estimate watershed-specific drought risk
and (b) to understand the recent changes in the streamflow variability across the New
England region, with a particular focus on the nature of surface runoff and baseflow
relationships. We use the multi-century reconstructed PDSI record to understand the
natural envelop of drought occurrence (severity and duration) in the state of Maine. A
new approach is developed to determine increasing or decreasing trend considering the
significance level in daily streamflow, baseflow and surface runoff and applied to the
abovementioned stations. In addition, clustering analyses is performed based on seasonal
baseflow Index and streams are classified into six groups. This work is a potential tool to
support the water managers in decision-making in different water sensitive sectors. An
improved understanding of sensitivity and severity of changes in surface runoff and
baseflow is certainly important to human and ecosystem use of streamflow. Future
changes, if examined in this framework, are likely to allow a reassessment of policy, a
great challenge in changing climate.