Quantifying Urban Groundwater in Environmental Field Observatories: A Missing Link in Understanding How the Built Environment Affects the Hydrologic Cycle

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0610009WeltyDespite the growing footprint of urban landscapes and their impacts onhydrologic and biogeochemical cycles, comprehensive field studies of urban water budgets are few.The cumulative effects of urban infrastructure (buildings, roads, culverts, storm drains, detentionponds, leaking water supply and wastewater pipe networks) on temporal and spatial patterns ofgroundwater stores, fluxes, and flowpaths are poorly understood. Any environmental observatorynetwork must include efforts to understand critical processes in urban landscapes, and urbangroundwater can fairly be characterized as a missing link in our understanding of the integratedfunctioning of the natural and built environment. The goal of this project is to develop expertise andanalytical tools for urban groundwater systems that will inform future environmental observatoryplanning and that can be shared with research teams working in urban environments elsewhere.Our work plan draws on a robust set of information resources in Maryland provided by ongoingmonitoring efforts of the Baltimore Ecosystem Study (BES), USGS, and the U.S. Forest Serviceworking together with university scientists and engineers from multiple institutions. Consent decrees,signed by both Baltimore City and Baltimore County with U.S. EPA to mitigate failures in the sanitarysewer network, are leading to increased deployment of rainfall, groundwater and wastewater flowsensors including wireless telemetry for real-time data collection. The proposed project will leveragethese resources with strategic investments in monitoring, modeling and database development toestablish protocols for quantifying groundwater systems in urban areas.A key concern is to bridge the gap between small-scale intensive field studies and larger-scale andlonger-term hydrologic patterns using synoptic field surveys, remote sensing, numerical modeling,data mining and visualization tools. Using the urban water budget as a unifying theme, we proposeto estimate the various elements of the budget in order to quantify the influence of urbaninfrastructure on groundwater. Proposed efforts include: (1) comparison of base flow behavior fromstream gauges in a nested set of watersheds at four different spatial scales from 0.8 to 171 km2, withdiverse patterns of impervious cover and urban infrastructure; (2) synoptic survey of well waterlevels to characterize the regional water table; (3) use of airborne thermal infrared imagery to identifylocations of groundwater seepage into streams across a range of urban development patterns; (4)use of seepage transects and tracer tests to quantify the spatial pattern of groundwater fluxes to thedrainage network in selected subwatersheds; (5) development of a mass balance for precipitationover a 170 km2 area on a 1x1 km2 grid using recording rain gages for bias correction of weatherradar products; (5) calculation of urban evapotranspiration using the Penman-Monteith methodcompared with results from an eddy correlation station; (7) use of numerical groundwater model in ascreening mode to estimate depth of groundwater contributing surface water flow; (8) data mining ofpublic agency records of potable water and wastewater flows to estimate leakage rates andflowpaths in relation to streamflow and groundwater fluxes; and (9) evaluation of the CUAHSIHydrologic Information Systems data modeling tools for application to urban environments.Broader Impacts. The project will provide guidance for development of environmentalobservatories, which are envisioned as providing critical information not only for basic science but formanagement of vital resources affecting the future health and well-being of both human populationsand ecosystems. The project also will contribute to the education of graduate and undergraduatestudents. Graduate students will participate as research assistants during the summer field season,as coordinated through UMBC's Center for Urban Environmental Research and Education. We willemphasize recruitment of undergraduate student assistants from UMBC's Meyerhoff Scholarsprogram, which has a national reputation for training of talented minority students committed tograduate education in science and engineering. Through the Baltimore Ecosystem Study LTER, anextensive outreach educational program managed by the BES education coordinator is already inplace with inner city Baltimore schools and with suburban Baltimore County schools, which includesa hydrologic science module within the environmental science curriculum. Results from theproposed work can contribute to/enhance this ongoing curriculum development effort.