New Hampshire and Vermont Water Use Estimates for 2005 and Projections for 2020
Background Information and Terms
Water is removed from surface water or groundwater to meet a need or demand of a water user. Withdrawals of groundwater or surface water go either directly to users (for example, via a well) to meet their demand or indirectly to users through a community water-system treatment and distribution system. A community water system (CWS) is a public water system that supplies water to the same population (at least 25 people or a minimum of 15 connections) year round. Public suppliers provide water for a variety of uses, such as domestic, commercial, industrial, thermoelectric power, and public water use. [More on public water systems from the U.S. Environmental Protection Agency.]
Water is provided to users to meet specific water-use needs or demands, such as, for domestic (household), commercial, or industrial purposes. Water demand can be estimated based on the type and size of water-use activity. For example, in estimating water demand for a hotel, the number of guest and conference rooms, restaurants, pools (swimming, Jacuzzi, sauna), and amount of lawn irrigation, fountains, and central air-conditioning are taken into account. The demand is met through a combination of self-supplied withdrawals and deliveries from community water systems. Current demand is the basis for projecting future withdrawals that need to meet the future demand. Data were collected or estimated for these categories of water use.
Consumptive use of water occurs primarily through evaporation or transpiration, or through incorporation of water into products or crops. How the water is used determines the rate of consumptive use. For example, bottling, an industrial process, has a high rate of consumptive use (up to 100 percent) because a high percentage of the withdrawn water is incorporated in the water, beer, soda, or other product being bottled. Apparel manufacturing has a low rate of consumptive use (less than 5 percent) because water is not an integral part of the production. The NH Seacoast study, using statistical techniques, developed a project-area average of 16 percent consumptive use for domestic demand. Knowledge of consumptive use is becoming increasingly important, because it represents water that is “lost” to water users in the immediate area.
Water is returned to surface-water or groundwater resources after use or wastewater treatment and, thus, becomes available for reuse. Community wastewater treatments systems (also known as Publicly Owned Treatment Works (POTW) in the National Pollutant Discharge Elimination System (NPDES) Program) include wastewater collection through sewers which convey wastewater to the treatment plant. Stormwater may also be conveyed to the treatment plant. After treatment, water is usually discharged to a stream, but can also be discharged to groundwater, or reclaimed for irrigation or non-potable cooling. Return flow can go directly to surface water, directly to groundwater through an injection well or infiltration bed, or indirectly to groundwater through septic systems. The amount of water returned is dependent on the amount of water “lost” to consumptive use. For example, a domestic withdrawal of 75 gal/d per person would result in an approximate return flow of 63 gal/d per person if the consumptive use rate is 16 percent.
USGS New Hampshire-Vermont Water Science Center web pages:
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