Large shifts in the magnitude of maximum annual streamflows have also been documented in many stream and river basins in New England. In addition, a shift toward higher winter flows and lower spring flows has been documented for the Connecticut River Basin as well as just to the north in New Hampshire at the Hubbard Brook Long Term Ecological Research Station using climate-driven streamflow simulations. Winter-spring peak flows occur approximately 6 days earlier compared to a century ago in Massachusetts and this trend is projected to continue during the 21st century. Because of this, the timing and magnitude of spring flows is shifting, which affects fish and other aquatic or wetland species that depend on flows and aquatic corridors for migration, spawning, development of early life stages, or other vital life cycle transitions. Warmer winter and early spring temperatures are leading to earlier snowmelt, more rain-on-snow episodes, and the breakup of winter ice on regional water bodies. Precipitation increases due to climate change do not appear to be changing low flows consistently across all seasons for example, there is evidence that more precipitation during late summer/early fall has increased low flows later in the fall. What constitutes a low or minimum flow varies by study, location, and season, but is generally the lowest flow for that site (excluding zero level flows or no water) over a defined time period (e.g., a week). “Low flows” play a crucial role in maintaining aquatic ecosystems as they provide a base level of flow (i.e., sustained flows composed of normal inputs from groundwater and precipitation) and help control stream water temperatures, particularly during summer. However, impacts will vary among basins based on:Īnnual average river and stream flow rates have increased during the last part of the 20th century throughout the Northeast region, even though peak flow rates have remained constant. Human structures that intersect with aquatic systems, such as dams, culverts, and road crossings, are potential barriers to fish and wildlife movement.Ĭlimate change directly impacts stream and river flows through changes in precipitation, temperature, and evapotranspiration ? (the sum of evaporation and the movement and exchange of water among plants, land, waterbodies, and the atmosphere). Hydrological conditions and the ability of aquatic species to travel from stream to stream (i.e., aquatic connectivity) are important for aquatic fish and wildlife survival. This has important implications for food-web structure and ecosystem function, such as making poor water quality events (e.g., excessive nutrient loading) and the incidence of waterborne disease more likely. Intensification of the hydrologic cycle (evaporation, condensation, precipitation, etc.) due to climate change and extreme precipitation events can increase the delivery of nutrients and pollutants to downstream and coastal habitats. Land use practices, water withdrawals for human use, and development are also influencing hydrological conditions of water bodies and aquifers. Climate-induced changes in precipitation, winter conditions, and extreme storm events have increased base and average stream and river flows in many parts of New England.
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