Dynamic Coupling of the Water Cycle with Patterns of Urban Growth

UMBC: C. Welty (PI), Andrew Miller, Bernadette Hanlon, Michael P. McGuire, Aditi Bhaskar, Kwabena Gyimah-Asante
Princeton: James Smith (PI), Mary Lynn Baeck
Shippensburg: Claire Jantz (PI), Scott Drzyzga
LLNL: Reed Maxwell (PI)
USGS: Gary Fisher (PI)


The objective of this project is to link an urban growth model (SLEUTH) with a fully-coupled, physically-based three-dimensional hydrologic model (PARFLOW-CLM) to evaluate the effects of growth on water availability and limits to water supply using the Baltimore metropolitan region as a case study. The urban growth modeling will consist of a rigorous and fully validated implementation of the SLEUTH model coupled with a spatial statistical model of urban suitability and demographic data. This approach will define a suitability map for urban land cover based on the conditions that are associated with current urban land and areas of recent urban land cover change. Landscape variables, such as soil suitability and non-urban land cover (e.g. forest and agriculture) will be used to define appropriate conditions for urbanization. Socio-economic variables, including lands that are protected through regulatory policies or parks, population density, and others, will also be included. In addition to providing a platform where both landscape characteristics and socio-economic variables can be integrated, this model will provide the opportunity to test and quantify the influence of each of these variables in either attracting or resisting development. Because the model will have a better representation of the landscape in terms of where development is more or less likely to occur, we also anticipate an improvement in the model’s performance. Implementation of the hydrologic component of the project will include intensive field studies at the local scale that will focus on a single highly urbanized watershed, Dead Run, which is a tributary to the Gwynns Falls, the primary study watershed of the Baltimore Ecosystem Study NSF-funded long-term ecological research site. Detailed process studies will be carried out in conjunction with application of the EPA SWMM model to achieve an integrated understanding of controls on water stores and fluxes at the subwatershed scale in a highly urbanized area. Subwatershed fine-scale modeling results results will then be used to determine large-scale effective properties as inputs to PARFLOW CLM of the entire metropolitan region. Combining a physically-based regional hydrologic model with an urban growth model will allow an assessment of the coupled feedbacks between growth projections (and the socio-economic variables that affect growth) and surface and subsurface water resources. Changes in stream baseflow and groundwater availability may in turn influence regulatory decisions on development permits in exurban areas.

A long-term goal of hydrologic modeling activities in the Baltimore region is to establish an “end-to-end system” of field-deployed sensors and sensor networks feeding real-time data into hydrologic models to enable prediction of water fluxes in streams and aquifers. One objective is to understand how the urban landscape and infrastructure partitions water in the components of the hydrologic cycle. This understanding is critical to quantifying biogeochemical cycles, a main focus of the BES LTER. This project will advance our objective of tying smaller-scale, process-based studies to a larger scale regional understanding of how the water cycle operates. This project will also advance several long-term goals for urban land cover modeling. Most significantly will be an opportunity to develop the links between urbanization and hydrologic systems in a spatially explicit context. The importance of water resource management to serve the public interest is a topic of growing importance to the State of Maryland precisely because of stresses induced by patterns of growth but with inadequate tools and insufficient data currently available to support decision-making. This work will help to close that gap. This effort is also of interest to the Chesapeake Bay program, in its work toward addressing questions about critical thresholds – e.g., when a critical threshold is reached and why, and what needs to be done to reach a sustainable condition. Interaction with state and local agency personnel will be carried out in order to incorporate their questions and policy concerns into modeling scenarios and to discuss the implications of our findings.