Human-dominated land uses can increase transport of major ions in streams due to the combination of human-accelerated weathering and anthropogenic salts. Calcium, magnesium, sodium, alkalinity, and hardness significantly increased in the drinking water supply for Baltimore, Maryland over almost 50 years (p<0.05) coinciding with regional urbanization. Across a nearby land use gradient at the Baltimore Long-Term Ecological Research (LTER) site, there were significant increases in concentrations of dissolved inorganic carbon (DIC), Ca2+, Mg2+, Na+, and Si and pH with increasing impervious surfaces in 9 streams monitored bi-weekly over a 3-4 year period (p<0.05). Base cations in urban streams were up to 60 times greater than forest and agricultural streams, and elemental ratios suggested road salt and carbonate weathering from impervious surfaces as potential sources. Laboratory weathering experiments with concrete also indicated that impervious surfaces increased pH and DIC with potential to alkalinize urban waters. Ratios of Na+ and Cl- suggested that there was enhanced ion exchange in the watersheds from road salts, which could mobilize other base cations from soils to streams. There were significant relationships between Ca2+, Mg2+, Na+, and K+ concentrations and Cl-, SO42-, NO3- and DIC across land use (p<0.05), which suggested tight coupling of geochemical cycles. Finally, concentrations of Na+, Ca2+, Mg2+, and pH significantly increased with distance downstream (p<0.05) along a stream network draining 170 km2 of the Baltimore LTER site contributing to river alkalinization. Our results suggest that urbanization may dramatically increase major ions, ionic strength, and pH over decades from headwaters to coastal zones, which can impact integrity of aquatic life, infrastructure, drinking water, and coastal ocean alkalinization.

We discuss the results of sampling baseflow and stormwater runoff in Watershed 263, an ultraurban catchment in west Baltimore City that is undergoing restoration aimed at both improving water quality as well as the quality of life in its neighborhoods. We focus on urban hydrology and describe the high baseflow and stormwater nutrient, metal, bacterial and other pollutant concentrations and loads seen in two 15 ha headwater storm drain catchments within WS263 that were sampled from 2004 to 2010. These data revealed several potentially important implications for watershed restoration efforts. First, the underground, or “buried stream” baseflow loads can be substantial, even relative to the surface urban runoff loads in highly impervious urban catchments. Second, the large pollutant load exports from these residential catchments suggest that older, highly urban landscapes may be important hotspots, as these small headwater catchments are numerous in the urban landscape. Third, the complex nature of the pollutant export patterns at the Baltimore and Lanvale catchments, both spatially and temporally, suggest that there may be complex drivers involved. Since this complexity may involve one or more systems of urban water networks, conceptualization in terms of the Urban Watershed Continuum (Kaushal and Belt, 2012) may be a useful tool to use both in their characterization and in designing interventions. Lastly, if these small headwater catchments truly represent a larger typology in terms of being hotspots, the characterization and mapping of older ultra-urban catchments may well be worthwhile given the large numbers of potential analogues in the urban landscape and the likely increasing role of aging infrastructure in creating more and larger “unseen” pollutant loads.

Older, economically troubled urban neighborhoods present multiple challenges to environmental quality. Here, we present results from an initiative in Baltimore, Maryland, where water-quality improvements were rooted in a socioecological framework that highlighted the interactions between biogeophysical dynamics and social actors and institutions. This framework led to implementation of best management practices followed by assessment of changes in human perception, behavior, and education programs. Results suggest that such an initiative can improve both water quality (eg reductions in nitrogen and phosphorus runoff) and quality of life (eg increased involvement in outdoor recreation by residents and improvements in student environmental literacy and performance) in urban neighborhoods. However, proposed solutions to the water-quality problems in such neighborhoods have (1) typically emphasized the need for stormwater facilities that are difficult to build and maintain and (2) comprehensively addressed neither the issues related to aging infrastructure and hydrologic complexity nor the benefits derived from linkages between resident perception of environmental improvements and behavior and water-quality outcomes.

Urban development remains an important agent of environmental change in the United States. The U.S. population grew by 17 percent from 1982 to 1997, while urbanized land area grew by 47 percent, suggesting that urban land consumption far outpaced population growth (Fulton and others, 2001; Sierra Club, 2003; American Farmland Trust, 2009). Eighty percent of Americans now live in metropolitan areas. Each American effectively occupies about 20 percent more developed land (for housing, schools, shopping, roads, and other related services) than 20 years ago (Markham and Steinzor, 2006). Passel and Cohn (2008) predict a dramatic 48 percent increase in the population of the United States from 2005 to 2050. The advantages and challenges of living in these developed areas—convenience, congestion, employment, pollution—are part of the day-to-day realities of most Americans. Nowhere are the environmental changes associated with urban development more evident than in urban streams. The U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program investigation of the effects of urban development on stream ecosystems (EUSE) during 1999–2004 provides the most spatially comprehensive analysis of stream impacts of urban development that has been completed in the United States. A nationally consistent study design was used in nine metropolitan areas of the United States—Portland, Oregon; Salt Lake City, Utah; Birmingham, Alabama; Atlanta, Georgia; Raleigh, North Carolina; Boston, Massachusetts; Denver, Colorado; Dallas, Texas; and Milwaukee, Wisconsin. A summary report published as part of the EUSE study describes several of these impacts on urban streams (Coles and others, 2012).

Urban development is an important agent of environmental change in the United States. The urban footprint on the American landscape has expanded during a century and a half of almost continuous development. Eighty percent of Americans now live in metropolitan areas, and the advantages and challenges of living in these developed areas—convenience, congestion, employment, pollution—are part of the day-to-day realities of most Americans. Nowhere are the environmental changes associated with urban development more evident than in urban streams. Contaminants, habitat destruction, and increasing streamflow flashiness resulting from urban development have been associated with the disruption of biological communities, particularly the loss of sensitive aquatic species. Every stream is connected downstream to larger water bodies, including rivers, reservoirs, and ultimately coastal waters. Inputs of chemical contaminants or sediments at any point along the stream can cause degradation downstream with adverse effects on biological communities and on economically valuable resources, such as fisheries and tourism. In response to general concerns about the degradation of urban streams, the U.S. Geological Survey (USGS) conducted a national-scale, scientific investigation of the effects of urban development on stream ecosystems. Nine metropolitan study areas of the United States were selected—Portland, Oregon; Salt Lake City, Utah; Birmingham, Alabama; Atlanta, Georgia; Raleigh, North Carolina; Boston, Massachusetts; Denver, Colorado; Dallas, Texas; and Milwaukee, Wisconsin. The studies were conducted in Salt Lake City, Birmingham, and Boston in 1999–2000; in Atlanta, Raleigh, and Denver in 2002–2003; and in Portland, Dallas, and Milwaukee in 2003–2004. The comprehensive investigation of all nine studies focused on three broad questions of interest to decision makers: What are the primary effects of urban development on stream ecosystems? How do the effects of urban development on stream ecosystems vary regionally across the country? Which urban-related stressors are most closely linked to biological community degradation, and how can multiple stressors be managed to protect stream health as a watershed becomes increasingly urbanized?

Conservation in urban areas typically focuses on biodiversity and large green spaces. However, opportunities exist throughout urban areas to enhance ecological functions. An important function of urban landscapes is retaining nitrogen thereby reducing nitrate pollution to streams and coastal waters. Control of nonpoint nitrate pollution in urban areas was originally based on the documented importance of riparian zones in agricultural and forested ecosystems. The watershed and boundary frameworks have been used to guide stream research and a riparian conservation strategy to reduce nitrate pollution in urban streams. But is stream restoration and riparian-zone conservation enough? Data from the Baltimore Ecosystem Study and other urban stream research indicate that urban riparian zones do not necessarily prevent nitrate from entering, nor remove nitrate from, streams. Based on this insight, policy makers in Baltimore extended the conservation strategy throughout larger watersheds, attempting to restore functions that no longer took place in riparian boundaries. Two urban revitalization projects are presented as examples aimed at reducing nitrate pollution to stormwater, streams, and the Chesapeake Bay. An adaptive cycle of ecological urban design synthesizes the insights from the watershed and boundary frameworks, from new data, and from the conservation concerns of agencies and local communities. This urban example of conservation based on ameliorating nitrate water pollution extends the initial watershed-boundary approach along three dimensions: 1) from riparian to urban land-water-scapes; 2) from discrete engineering solutions to ecological design approaches; and 3) from structural solutions to inclusion of individual, household, and institutional behavior.

The Water and Watersheds program has made significant and lasting contributions to the basic understanding of the complex ecological system of Baltimore, MD. Funded at roughly the same time as the urban Long- Term Ecological Research (LTER) project in Baltimore, the Water and Watersheds grant and the LTER grant together established the Baltimore Ecosystem Study (BES) in 1997. This joint project took advantage of three conspicuous stream catchments and the direct harbor drainage in metropolitan Baltimore. Not only the watersheds themselves, but the community and political interest in those watersheds were crucial to the success and application of our project.

Chloride concentrations are increasing at a rate that threatens the availability of fresh water in the northeastern United States. Increases in roadways and deicer use are now salinizing fresh waters, degrading habitat for aquatic organisms, and impacting large supplies of drinking water for humans throughout the region. We observed chloride concentrations of up to 25% of the concentration of seawater in streams of Maryland, New York, and New Hampshire during winters, and chloride concentrations remaining up to 100 times greater than unimpacted forest streams during summers. Mean annual chloride concentration increased as a function of impervious surface and exceeded tolerance for freshwater life in suburban and urban watersheds. Our analysis shows that if salinity were to continue to increase at its present rate due to changes in impervious surface coverage and current management practices, many surface waters in the northeastern United States would not be potable for human consumption and would become toxic to freshwater life within the next century.

The City of Baltimore received a National Pollutant Discharge Elimination System (NPDES) municipal storm water permit in January 1994. A major effort under the permit was to develop a program to identify and eliminate illicit entries into the municipal storm water system. Approximately one third of the storm drain outfalls have been targeted under this program. The outfalls correspond to sections of the storm drain system inspected for the development of a storm drain infra-structure data base. During the infra-structure inspections, samples were collected and flow measurements were taken at storm water outfalls. Any suspended illicit discharges were sent to the laboratory where they were analyzed for a suite of toxicants and other pollutants include: surfactants, phenols, ammonia, copper, lead, zinc, residual chlorine and total petroleum hydrocarbons. The laboratory data provided the basis for ranking the subwatersheds from least to most polluted. These rankings were then used to design a dry weather sampling program so that the most polluted watersheds are sampled more frequently (e.g., monthly) than the least polluted (annually). Repeated high pollution levels initiate an investigation at sequential sampling points upstream until the pipe segment receiving the discharge is identified. A geographical information system is used to assistmore » in identifying potential sources of contamination (e.g., industries) in the suspected drain segment.« less

ABSTRACT Measurement of pollutant loadings is important in any lake management program. The flow interval method is among the most widely used today for this purpose. However, the Baltimore City Water Quality Management Office found this methodology to be extremely sensitive to the unit of flow (e.g. daily average, 15 minute discrete records) used in the computation. In three tributaries monitored, errors attributable to the flow unit used in phosphorus and sediment loading computations were found to be as high as 44 percent and 71 percent, respectively. Potential errors are greatest for streams with flashy hydrographs and a strongly positive flow/concentration relationship. The degree to which phosphorus and sediment loads are underestimated by using daily averaged flows varies with watershed, hydrologic year, and flow-concentration dynamics.