U.S. Department of Energy - Energy Efficiency and Renewable Energy
Federal Energy Management Program
Guidance for Developing Baseline and Annual Water Use
Potable water use intensity is defined as annual potable water use divided by total gross square footage of facility space (gal/ft2). The facility gross square footage is the same value used for energy use intensity reduction goals.
Executive Order (E.O.) 13423 requires Federal agencies to develop a potable water use intensity baseline for fiscal year (FY) 2007. Agencies must report total potable water consumption and gross facility square footage against that baseline.
To avoid additional reporting requirements, E.O. 13423 does not require agencies to report square footage of irrigated turf or landscape. Potable water used for landscape irrigation must be reported in total potable water use, but the amount of turf or landscape area is not included in the gross square footage reporting. This elevates the water use intensity of facilities with irrigated grounds while still accurately reflecting water consumption.
E.O. 13514 mandates a new baseline in addition to FY 2007 potable water use intensity. Federal agencies must develop a baseline for industrial, landscaping, and agricultural water use in FY 2010. This new baseline is a total volumetric summation of industrial, landscaping, and agricultural water consumed. Federal agencies are required to report water used in these categories that are not currently reported in the potable water use intensity baseline and subsequent reporting. The intent is to expand the water reduction of Federal agencies to include other areas of freshwater consumption beyond potable water.
FEMP released voluntary Guidelines for Estimating Unmetered Landscaping Water Use (PDF 632 KB) to help Federal agencies determine landscaping water use in unmetered situations per Executive Order 13514. Download Adobe Reader.
Federal Site Baseline and Annual Water Use Development
A Federal agency's reported total water use is only as good as the data collected from the individual sites. The following information is intended to help Federal sites develop a sound water use baseline and subsequent annual water use intensity.
Federal sites can calculate water use from a variety of sources:
- Water utility metered data
- Facility sub-metered data
- On-site water production metered data
- Unmetered facility or equipment based on engineering estimates
Water Utility Metered Data
Many Federal sites purchase water from a local water utility and can determine the total potable water use from the "master" utility meter. If there are multiple utility meters, such as irrigation and facility meters, or more than one utility providing water, make sure you include all metered water use.
Facility Sub-Metered Data
Some sites may have meters/sub-meters on individual buildings, equipment, or processes (e.g., cooling towers or irrigation). The data from meters can be used to reconcile the total water use reported by the utility and creating a water balance on your facility.
On-Site Water Production Data
Some large Federal sites produce their own water from local wells or surface water, such as lakes or streams. The best way to determine water use of these sources is to have production meters installed.
In the absence of water meters, well production can be estimated using pump flow rates at the given well depth multiplied by known run-time. Pump flow rate data is typically specified at design. Runtime can be monitored easily and inexpensively for representative intervals and then applied to annual calculations. Federal sites producing their own water are requested to report water use data consistent with their agency's respective measuring methods (i.e., the use of daily logs, metered data, or flow estimates). The intent is to account for and record the amount of water the agency is currently using relative to its established baseline consumption.
Unmetered Facility or Equipment
Federal facilities that do not have water metering must estimate their water use. Unmetered facilities should have priority for a water auditing facility and support the installation of metering to the extent that it enables both baseline development and annual water use reduction. Until this can be accomplished, some estimates may be required to calculate water use in these unmetered areas. The following useful techniques can be used to estimate water use:
Federal water use indices: Helps agencies estimate water use by facility type. Water use indices provide typical ranges of water consumed in a specific facility type based on the number of occupants in the facility. Using water use indices can provide a quick way of determining an estimate of water used in your facilities, but these indices do not take into account regional variances.
Batch procedure: Estimates water use for a process or application that uses a given amount of water in each batch. For example, water used in dust suppression on a construction site can be estimated by multiplying the total volume of water held in a dust suppression truck or tank by the total numbers of truck loads that is used per day.
Discharge procedure: Estimates water use based on the flow rate and the run-time of the equipment. For example, to determine the total water used for irrigation, the sprinkler head flow rate (in gallons per minute) can be multiplied by the weekly run-time (in minutes) to estimate the total water use for each week (in gallons).
Ensure consistent units are used when estimating annual water use. If you purchase water from a local water utility, make sure you understand the units that are reported. For example, some utilities use thousand gallons (Kgal) or cubic feet of water. Some utilities have their own special units. If you have different water sources with different units, make sure to use appropriate conversion factors to sum the total water use.
Document the assumptions and estimating techniques used so that they can be repeated in coming years to measure progress towards reduction goals. Documenting the adjustment made to baseline consumption data is equally important, once efforts are implemented to account for unmetered facilities either through metering or estimating techniques. All baseline adjustments must be documented and submitted with annual data reports.