Impacts of climate change on water resource-related sectors
Session chair: Tom Huntington, USGS
Session abstracts:
Conserving Freshwater and Coastal Resources in a Changing Climate
Elizabeth Grubin (student), Abigail Hardy (student), Regina Lyons (student), Amelia Schmale (student), Takeo Sugii (student)
Urban and Environmental Policy and Planning, Tufts University
The effects of climate change have already been seen, including changes in global average air and ocean temperatures, a rise in sea levels, an increase in precipitation in some areas and droughts in others, and an increase in the occurrence of intense weather events. These impacts are projected to continue into the future, and will dramatically impact aquatic ecosystems. This project was produced for The Nature Conservancy (TNC) and examines the vulnerability to climate change of three types of aquatic ecosystems: freshwater, wetland, and coastal regions, which occur in the eastern region of the United States. This report identifies technological tools, such as mapping and modeling techniques, and adaptation measures, such as land use regulation and ecosystem restoration methods, that are available for analyzing and adapting to impacts of climate change. We make a series of recommendations to TNC that will promote understanding and conservation of aquatic ecosystems including: specific areas where more research is needed, investment in modeling and mapping technologies to promote more accurate analysis of ecosystems to inform conservation decisions, the use of conservation oriented land-use policies, and collaboration with regional agencies to promote regional planning that integrates climate change concerns.
Internal Phosphorus Cycling in Maine Lakes: Implications due to global warming
Bjorn Lake1, Aria Amirbahman1, and Stephen Norton2
1 Dept. of Civil and Environmental Engineering, University of Maine, Orono, ME
2 Dept. of Earth Sciences, University of Maine, Orono, ME
Global warming will affect the water quality of Maine lakes. Processes within lakes that supply the water column with nutrients during the summer months will be altered by enhanced thermal stratification, solar irradiation, and microbial activity. Our current research has focused on understanding the mechanisms which lead to internal loading of phosphorus (P) in Maine lakes. We have utilized a combination of water column data and chemical characterization of sediments to delineate the parameters that lead to internal P loading in a diverse set of lakes. These characteristics are the degree of anoxia during the summer months, the iron and aluminum content of the sediment, and the microbial mineralization of organic P compounds. With this knowledge, we can surmise the effect warmer temperatures will have on P availability in Maine lakes.
The geologic variables that affect saltwater intrusion in coastal wells in fractured bedrock
Robert G. Gerber
Sebago Technics, Inc., Westbrook, ME
Localized saltwater intrusion into coastal fractured bedrock aquifers has already been documented through a number of coastal town-wide studies the author has conducted over the past 30 years. With the expected rise in sea level due to global warming more wells will be at risk. Given the difficulty, energy, and expense required to remove salt from water, it is important for land use planners to know which geologic factors increase the chances of saltwater intrusion. Using the USGS density-dependent groundwater model SEAWAT2000 in several environments, the author will describe geologic conditions that enhance the chances of saltwater intrusion. The extent of inland saltwater intrusion is inversely proportional to the distance to the groundwater divide and to the precipitation recharge rate between the ocean and the divide. It is also inversely related to the thickness of sediments covering the intertidal and subtidal area but directly related to the vertical permeability of these sediments. The greater the ratio of the distance to the groundwater divide divided by the width of an estuarine channel, the less the chance of saltwater intrusion. Fracture anisotropy and single high-transmissivity fracture orientations also affect the likelihood of saltwater capture. Other evaluations are in progress and will be reported at the conference. One could use these factors to develop guidelines for allowable coastal residential development densities where the water supply relies on drilled wells.
Evidence for Changing Flood Risk in New England since the Late 20th Century
Mathias J. Collins
NOAA Restoration Center, Gloucester, MA
Long-term flow records for watersheds with minimal human influence have shown trends in recent decades toward increasing streamflow at regional and national scales, especially for the lower flow quantiles like the annual minimum and annual median flows. Trends for higher flow quantiles are less clear, despite recent research showing increased precipitation in the coterminous United States over the last century that has been brought about primarily by an increased frequency and intensity of events in the upper 10th percentile of the daily precipitation distribution— particularly in the Northeast. This study investigates trends in 28 long-term annual flood series for New England watersheds with dominantly natural streamflow. The flood series are an average of 75 years in length and are continuous through 2006. Twenty-five series show upward trends via the non-parametric Mann-Kendall test, forty percent (10) of which are statistically significant (p<0.1). Moreover, an average standardized departures series for 23 of the study gages indicates that increasing flood magnitudes in New England occurred as a step change around 1970. The timing of this is broadly synchronous with a phase change in the low frequency variability of the North Atlantic Oscillation (NAO), a prominent upper atmospheric circulation pattern that is known to effect climate variability along the United States east coast. Identifiable hydroclimatic shifts should be considered when the affected flow records are used for flood frequency analyses. Special treatment of the flood series can improve the analyses and provide better estimates of flood magnitudes and frequencies under the prevailing hydroclimatic condition.
