3.1 Chesapeake Bay Program Watershed Model
The spatial units of analysis for this ICPRB project are the watershed-based “river
segments” (Fig. 2) developed for the Chesapeake Bay Program (CBP) Watershed
Model [20, 21]. The CBP Watershed Model, an open-source modeling tool based
on the Hydrologic Simulation Program—FORTRAN (HSPF), simulates flows and
concentrations of nutrients and sediment in streams flowing within the Bay watershed, which includes the Potomac River Basin. Several organizations, including
ICPRB, have adopted the CBP Watershed Model as a water supply planning tool
[13, 18]. The CBP Watershed Model’s streamflow and pollutant concentration
estimates are provided by river segment, and some model inputs, including water
supply withdrawals and wastewater treatment plant discharges, are also aggregated
by river segment. The delineation of the river segments is based primarily on
considerations of data availability. The choice of the river segments as spatial
units of analysis for our project provides a convenient interface with the CBP
Watershed Model.
3.2 Water Balance Conveyance Model
To compute consumptive use for a given spatial unit, a Water Balance Conveyance
Model was constructed to route water flow from raw water withdrawal points to
wastewater discharge points and to track consumptive losses and return flows along
the way. This model was developed specifically to address the complexities often
present in public water supply and wastewater treatment systems and the interactions of public systems with self-supplied facilities or with other public systems.
The tool for consumptive use relies on withdrawal data provided by each state
within the Potomac Basin. However, the states’ data differ in the time period of data
availability, collection methods, and categorization of water uses. One benefit of
this effort is the compilation of state data into a single location that allows Potomac
water use to be understood as a whole.
The developed tool incorporates three features to facilitate a collaborative
planning process: transparency, flexibility, and accessibility. The interactive mapping component of the tool will promote transparency by allowing stakeholders to
view and access basin-wide water use data. The underlying database incorporates a
flexible design that allows the addition of site-specific water consumption data as it
becomes available, and in the absence of site-specific data, relies on regional and
national data. Finally, the tool is being developed using open-source database and
mapping software, making it widely accessible to all stakeholders. Section 3.6
provides details of the ICPRB Water Balance Conveyance Model configuration.
Interactive Geospatial Analysis Tool for Estimating Watershed-Scale. . .
147
The spatial units of analysis for this ICPRB project are the watershed-based “river
segments” (Fig. 2) developed for the Chesapeake Bay Program (CBP) Watershed
Model [20, 21]. The CBP Watershed Model, an open-source modeling tool based
on the Hydrologic Simulation Program—FORTRAN (HSPF), simulates flows and
concentrations of nutrients and sediment in streams flowing within the Bay watershed, which includes the Potomac River Basin. Several organizations, including
ICPRB, have adopted the CBP Watershed Model as a water supply planning tool
[13, 18]. The CBP Watershed Model’s streamflow and pollutant concentration
estimates are provided by river segment, and some model inputs, including water
supply withdrawals and wastewater treatment plant discharges, are also aggregated
by river segment. The delineation of the river segments is based primarily on
considerations of data availability. The choice of the river segments as spatial
units of analysis for our project provides a convenient interface with the CBP
Watershed Model.
3.2 Water Balance Conveyance Model
To compute consumptive use for a given spatial unit, a Water Balance Conveyance
Model was constructed to route water flow from raw water withdrawal points to
wastewater discharge points and to track consumptive losses and return flows along
the way. This model was developed specifically to address the complexities often
present in public water supply and wastewater treatment systems and the interactions of public systems with self-supplied facilities or with other public systems.
The tool for consumptive use relies on withdrawal data provided by each state
within the Potomac Basin. However, the states’ data differ in the time period of data
availability, collection methods, and categorization of water uses. One benefit of
this effort is the compilation of state data into a single location that allows Potomac
water use to be understood as a whole.
The developed tool incorporates three features to facilitate a collaborative
planning process: transparency, flexibility, and accessibility. The interactive mapping component of the tool will promote transparency by allowing stakeholders to
view and access basin-wide water use data. The underlying database incorporates a
flexible design that allows the addition of site-specific water consumption data as it
becomes available, and in the absence of site-specific data, relies on regional and
national data. Finally, the tool is being developed using open-source database and
mapping software, making it widely accessible to all stakeholders. Section 3.6
provides details of the ICPRB Water Balance Conveyance Model configuration.
Interactive Geospatial Analysis Tool for Estimating Watershed-Scale. . .
147