Researchers' Working Meeting on Climate Change Impacts
in the Mid-Atlantic Region
Penn State--June 8-9, 1998

FRESHWATER RESOURCES

(Summary prepared by Heejun Chang and Rob Neff)

Panel:

Chair - Brent Yarnal, Penn State
Ana Barros, Penn State
James Lynch, Penn State
Lee Mulkey, U.S. EPA, National Risk Management Research Lab
Gary Peterson, Penn State

The Water Working Group of the Mid-Atlantic Regional Assessment has three main emphases: 1) geographical, 2) climate, and 3) water resources. The geographical emphasis is on fresh water in river basins. Study objects are rivers, streams, lakes, groundwater, and soil moisture. Anything that has salt water such as estuaries will be left to the Coastal Working Group. The emphasis on climate centers on two key climatic variables: precipitation and temperature. It is important to understand how their short-term variation affects water resources, as well as how water resources are affected by long-term changes in their average values. Short-term variation and long-term changes in precipitation affect the occurrence of "moisture" droughts (such as the droughts experienced in the 1960s and, more recently, in the summer of 1995), floods, and severe storms. Variations and changes in average temperature are also important in terms of severe droughts related to intense heat. This type of drought, during which precipitation is often near "normal," is the most common and occurred most recently during the summer of 1988. The emphasis on water resources embraces various issues, including demand, supply, quality, emergency management and land use. Supply includes potential (natural control) and actual water supply (institutional control). It is important to compare both the potential and actual water supply to demand, which will depend on population and economic changes. Emergency management related to floods and droughts will also be studied. While there is scattered expertise on water quality and land use at Penn State, the group feels these are topics for which it needs the most outside help.

The group hopes to answer two broad questions: (1) How do climate variation, droughts, floods, and severe storms affect water supply, demand, and quality? and (2) How will climate change affect droughts, floods, water supply, demand, and quality?

The nature of water resources planning and management in the US has changed over time. Economic efficiency was the main goal of most water-related policy in the early twentieth century. The 1950-60 period focused on intragenerational equity issues such as regional income redistribution. In the 70s and 80s, decision making on water-resources management reflected growing environmental concern. Health and protection and restoration of good water quality became major issues. More recently, general social well-being has emerged as a important issue in water-resources planning.

Prediction of climate variability, which entails uncertainty and requires long-term historical data, is a major challenge in water-resources management. In the case of data gaps, relationships can be drawn between the study area and similar regions for which data are more plentiful. For example, water resources planners in the early twentieth century used Nile River data on precipitation and flow to find a relationship between big floods and precipitation for the Mississippi River. Recent work attempts to demonstrate a link between occurrences of big floods and ENSO indices. While such a relationship cannot be demonstrated clearly using correlation, graphic analysis does show a relationship between strong ENSO events and Mississippi River flow.

Uncovering spatial-temporal relations in climate variability is another crucial task in water resources planning. Previous studies on the Susquehanna River Basin (SRB) suggest a relationship between the spatial variability of rainfall, the spatial and temporal variability of floods, and sediment production and how it is controlled by a dam. These findings are important in reevaluating the traditional role of a dam and designing a new dam.

Relating changes in precipitation resulting from climate change to changes in river flow will be difficult due to the uncertainty in GCM predictions. Present GCMs are not able to predict specific precipitation intensities at specific locations. However, Barros believes the prediction of changes in overall variability could be used with past-processing techniques to infer runoff and streamflow. She suggests that the Water Group’s analysis should focus on climate variation and risk, which have been neglected in recent water-management decisions.

Cumulative watershed effects should be considered in analyzing watersheds with various sizes and locations. Because individual streams may respond differently to climate change depending on their surrounding environment and incremental impacts, understanding these effects is a first step to predicting future changes in different watersheds. In headwaters such as forested first-order basins, surface land characteristics may be more critical than groundwater components. Farther downstream, groundwater components and characteristics of surrounding areas may be more important than site characteristics.

Water quality also depends on location. The rate of sediment deposition and the effects of land-use change, which affect the water quality of a stream, differ upstream and downstream. Non-point source pollution may be minimal in headwaters, while both point and non-point sources may be important downstream. Different parameters produce different impacts, and we should take this into account in analyzing the climate change impacts in different watersheds. It is also important to consider the different effects of temporal scales and time lag on stream water quality. Climate is just one of many components that affect water quality.

Modeling atmospheric deposition of contaminants is complex, and low spatial resolution of the required data is a big problem in predicting effects on water quality. Interfacing precipitation data with maps of atmospheric concentrations of these contaminants can improve spatial resolution, but requires assumptions about the relationship between these variables and the resulting atmospheric deposition. In general, changes in atmospheric deposition are related to changes in anthropogenic emissions of pollutants. While emissions of sulfur dioxide are declining, there are still concerns over nitrous oxides and eutrophication. Atmospheric deposition of ammonia is a growing problem, especially in the eastern US. Other issues that warrant study are the impacts of atmospheric concentrations of atrazine and triazines on the food web and the effects of trace metals. Amphibians are good indicators of the effects of changes in water chemistry, water volume and solar radiation on ecosystems.

Analysis of these effects will be complicated by long-term influences from nature and past land uses. The "signal" of climate change-related impacts of water quality may be easier to identify in headwaters, where anthropogenic influences have a less confounding impact.

Air and water quality are vulnerable to climate change, largely to the extent that the pollution control infrastructure processes the climate "signal." This observation is also true for water resources (e.g. water supply, flood control).

It is important to calculate sensitivity functions in assessing regional impacts of climate change. A sensitivity function identifies relationships between changes in climate variables and relevant consequence variables. Which sensitivity functions are the most appropriate in addressing regional impacts of climate change? If there is a "threshold" effect, that needs to be identified and, if possible, quantified. One focus should be on human health (for instance, pathogen survival as it relates to climate variability is important). However, we must be careful to not be so selective as to bias the results of our analysis, especially because there could be positive as well as negative impacts. "Red flags" may attract attention, but it is important to pose testable hypotheses about the relationship between climate variability and potential impacts. This also can be considered in the context of whether or not more (or less) infrastructure investment will be needed as a result of climate change, in order to maintain air and water quality.

The regional impacts of changing human activities on water quality can be examined by assessing nutrient loads using Geographic Information System (GIS)-based empirical models. Variables include different types of land use, changes in land use (for example, the trend towards factory farms and urbanization), runoff, septic systems, fertilizer usage, and atmospheric deposition. There have been and continue to be significant changes from agricultural to urban land use, and this has proved to be a critical factor in degrading water quality. Changes in soil organic matter and soil nutrient concentrations are also important. It is difficult to judge to what extent climate change will affect soils, and hence, water quality – some factors that are not be directly climate-related may be the most important for water quality in this region. It is important to identify these factors to understand how anthropogenic influences affect water quality now before predicting the influence climate change may have. It is also important to consider second order impacts of climatic effects on agriculture in other regions such as the Midwest, since a substantial amount of animal feed is imported from outside the Mid-Atlantic Region.

A wealth of data is available for Pennsylvania through PAMAGIC and PASDA (http://www.pasda.psu.edu). Some of these data sets may be available for other states in the region at lower spatial resolutions. Dr. Yarnal suggested that data used in the analyses will have to be determined using a "lowest common denominator" approach, with the spatial resolution determined by data availability for the entire region.

Barros pointed out an example of climate impact on soils: the deposition of large amounts of sand on productive land in the Mississippi during 1993. Also, changes in rainfall intensity affect the mobility of upper soil layers, which in turn affects water quality.