3.2.1 Data Identification
The data used include monthly time series of consumptive use estimates for 1985–
2012 by water use type (e.g., public water supply, commercial, industrial). This
captures the seasonal variation of water use in the basin and long-term trends and
allows for comparisons of water use in drought and non-drought years. Streamflow
from the upper basin is measured at the USGS gauge on the Potomac River at Little
Falls.
3.3 Definition of Consumptive Use
For this effort, consumptive water use is defined as the amount of water associated
with a withdrawal for water supplies (domestic, industrial, and agricultural uses)
from a given resource that is not returned to the same resource and is thus
unavailable to other users or aquatic communities [10, 22–26]. Return flows may
be less than withdrawals for a variety of reasons: losses due to evaporation or
transpiration, incorporation of water into products or crops, or consumption by
humans or livestock [22]. This definition of consumptive water use includes all
types of “blue” water (water present in aquifers, lakes, reservoirs, and streams) but
excludes “green” water (water stored in the soil or within vegetation that is
ultimately evaporated and transpired) [27, 28]. The definition is limited to blue
water since its use in the Potomac Basin is subject to influence by management
strategies. Consumptive use from blue water sources used for irrigation is also
considered in this study. By the above definition of consumptive use, a withdrawal
may also be consumptive if it occurs from a given resource and its associated return
flow is discharged to a different resource (often referred to as an inter-basin
transfer). Thus, the specification of spatial scale is integral to the concept of
consumptive use.
For an individual facility, for example, a commercial or industrial facility that
withdraws, uses, and discharges (return flow) water at the same location, consumptive use can be expressed by a simple water balance equation:
CU ¼ W À R
ð1aÞ
where
CU ¼ consumptive use
W ¼ water withdrawn
R ¼ water returned
Equation (1a) can be used to compute the facility’s consumptive use when
withdrawal and discharge data are available and under the assumption that inflows
and outflows due to leakage are not significant. Consumptive use results computed
148
J. Ducnuigeen et al.
The data used include monthly time series of consumptive use estimates for 1985–
2012 by water use type (e.g., public water supply, commercial, industrial). This
captures the seasonal variation of water use in the basin and long-term trends and
allows for comparisons of water use in drought and non-drought years. Streamflow
from the upper basin is measured at the USGS gauge on the Potomac River at Little
Falls.
3.3 Definition of Consumptive Use
For this effort, consumptive water use is defined as the amount of water associated
with a withdrawal for water supplies (domestic, industrial, and agricultural uses)
from a given resource that is not returned to the same resource and is thus
unavailable to other users or aquatic communities [10, 22–26]. Return flows may
be less than withdrawals for a variety of reasons: losses due to evaporation or
transpiration, incorporation of water into products or crops, or consumption by
humans or livestock [22]. This definition of consumptive water use includes all
types of “blue” water (water present in aquifers, lakes, reservoirs, and streams) but
excludes “green” water (water stored in the soil or within vegetation that is
ultimately evaporated and transpired) [27, 28]. The definition is limited to blue
water since its use in the Potomac Basin is subject to influence by management
strategies. Consumptive use from blue water sources used for irrigation is also
considered in this study. By the above definition of consumptive use, a withdrawal
may also be consumptive if it occurs from a given resource and its associated return
flow is discharged to a different resource (often referred to as an inter-basin
transfer). Thus, the specification of spatial scale is integral to the concept of
consumptive use.
For an individual facility, for example, a commercial or industrial facility that
withdraws, uses, and discharges (return flow) water at the same location, consumptive use can be expressed by a simple water balance equation:
CU ¼ W À R
ð1aÞ
where
CU ¼ consumptive use
W ¼ water withdrawn
R ¼ water returned
Equation (1a) can be used to compute the facility’s consumptive use when
withdrawal and discharge data are available and under the assumption that inflows
and outflows due to leakage are not significant. Consumptive use results computed
148
J. Ducnuigeen et al.