Scientific Investigations Report 2007–5157

Methods for and estimates of 2003 and projected water use in the Seacoast Region, Southeastern New Hampshire

U.S. Geological Survey, Scientific Investigations Report 2007–5157

By Marilee A. Horn, Richard B. Moore, Laura Hayes, and Sarah M. Flanagan

Prepared in cooperation with the New Hampshire Department of Environmental Services


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New methods were developed to estimate water use in 2003 and future water demand in 2017 and 2025 in the Seacoast region in southeastern New Hampshire, which has experienced a 37-percent population increase during 1980 to 2000. Water-use activities for which estimates were developed include water withdrawal, delivery, demand, consumptive use, release, return flow, and transfer by registered and aggregated unregistered (less than 20,000 gallons per day (gal/d)) users at the census-block and town scales.

Estimates of water use rely on understanding what influences water demand and its associated consumptive use, because changes in demand and consumptive use affect withdrawal and return flow. Domestic water demand was estimated using a per capita water-demand model that related metered deliveries to domestic users with census block and block-group data. The model was used to predict annual, summer, and winter per capita water-demand coefficients for each census block. Significant predictors of domestic water demand include population per housing unit, median value of owner-occupied single family homes, median year of housing construction (with 1900 as the base value), population density, housing unit density, and proportion of housing units that are in urban areas. Mean annual domestic per capita water-demand coefficient in the Seacoast region was 75 gal/d; the coefficient increased to 92 gal/d during the summer and decreased to 63 gal/d during the winter. Domestic consumptive use was estimated as the difference between annual and winter domestic water demand. Estimates of commercial and industrial water demand were based on coefficients derived from reported use and metered deliveries. Projections of water demand in 2017 and 2025 were determined by using the housing and employee projections for those years developed through a Travel Demand Model and applying current domestic and non-domestic coefficients.

Water demand in 2003 was estimated as 26.3 million gallons per day (Mgal/d), 35 percent of which was during the summer months of June, July, and August. Domestic water demand was 19.0 Mgal/d (72 percent), commercial water demand was 3.7 Mgal/d (14 percent), industrial water demand was 2.9 Mgal/d (11 percent), irrigation water demand was 0.4 Mgal/d (1 percent), and thermoelectric, mining, and aquaculture water demand was 0.3 Mgal/d (1 percent). Domestic consumptive use for the Seacoast region was 16 percent of domestic water demand, which translates to a loss of 3 Mgal/d over the entire Seacoast region.

In 2003, water withdrawal was 771.3 Mgal/d, of which 742.2 Mgal/d was instream use for hydroelectric power generation and thermoelectric power cooling. The remaining 29.1 Mgal/d was withdrawn by community water systems (20.3 Mgal/d; 70 percent), domestic users (6.5 Mgal/d; 22 percent), commercial users (1.0 Mgal/d; 3 percent), industrial users (1.0 Mgal/d; 3 percent), irrigation (0.2 Mgal/d; 1 percent) and other users (less than 0.1 Mgal/d).

Return flow for 2003 was 774.0 Mgal/d, of which 742.2 Mgal/d was returned following use for hydroelectric power generation and thermoelectric plant cooling. The remaining 31.8 Mgal/d was returned by community wastewater systems (21.0 Mgal/d; 66 percent), domestic users (8.0 Mgal/d; 25 percent), commercial users (1.2 Mgal/d; 4 percent), industrial users (0.8 Mgal/d; 3 percent), and other users (0.1 Mgal/d).

Domestic water demand is projected to increase by 54 percent to 28.7 Mgal/d from 2003 to 2025 based on projection of future population growth. Non-domestic (commercial, industrial, irrigation, and mining) water demand is projected to increase by 62 percent to 11.8 Mgal/d from 2003 to 2025.

Suggested Citation

Horn, M.A., Moore, R.B., Hayes, Laura, Flanagan, S.M., 2008, Methods for and estimates of 2003 and projected water use in the Seacoast region, southeastern New Hampshire: U.S. Geological Survey Scientific Investigations Report 2007–5157, 87 p., plus 2 appendixes on CD-ROM.

For further information, contact:


U.S. Geological Survey

New Hampshire-Vermont Water Science Center

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Pembroke, NH 03275

(603) 226-7807

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