metropolitan area suppliers and by the suppliers upstream of the metropolitan area.
The graph also shows the consumptive use of the upstream suppliers.
4.2 Significance of Inter-Watershed Transfers
The significance of inter-watershed transfers in some parts of the Potomac Basin is
illustrated in Fig. 8, which shows consumptive use in the Monocacy sub-basin
computed by two different methods. The Monocacy sub-basin includes portions of
Frederick and Carroll counties in Maryland and Adams County in Pennsylvania.
Figure 8a shows consumptive use in August 2012 estimated assuming onsite return
flow, i.e., assuming that any discharge of wastewater occurs in the same watershed
as the associated withdrawal. Figure 8b shows consumptive use for the same month,
computed using the Water Balance Conveyance Model described in Sect. 3.6. The
results capture the significant transfers of water that occurs in this sub-basin.
Municipalities and other users in Frederick County, who formerly relied upon the
Monocacy River, are increasingly turning to the Potomac River as a more reliable
water supply. However, most municipal WWTPs in the county still discharge to the
Monocacy River and its tributaries.
Fig. 8 Consumptive use in the Monocacy sub-basin by river segment, calculated assuming onsite
return flow for all withdrawals (a) and by the Water Balance Conveyance Model (b). A negative
consumptive use value indicates a net importation of water into the area (Source: River segments
from CBP)
Interactive Geospatial Analysis Tool for Estimating Watershed-Scale. . .
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