Where Puerto Rico's Freshwater Comes From and Where It Goes, 2010

The municipios of Puerto Rico. USGS.

Why track water use

Water diverted from streams and pumped from wells supplies Puerto Rico's 78 municipios. Farms, households, industry, commerce and mining all draw on reservoirs, streams and aquifers, and managers need accurate figures to protect them.

• From 2000 to 2010, the population fell 2.6 percent, from 3.8 to 3.7 million, easing demand.
• Rising water rates, low-flow fixtures and conservation programs cut household use per person.
• Almost 99 percent of residents were on public supply in 2010, from the Puerto Rico Aqueduct and Sewer Authority (PRASA) or smaller community-run (non-PRASA) systems.

Sources

The figures cover offstream use — water withdrawn from a river or aquifer and carried to where it is used. In 2010 Puerto Rico withdrew 733.16 million gallons a day (Mgal/d) of freshwater.

Uses

Domestic — drinking, cooking, bathing, laundry, dishes, toilets, cars, lawns and gardens:

• PRASA delivered 198.31 Mgal/d to 3.7 million people (15.25 from groundwater, 183.06 from surface water) — about 55 gallons a day per person.
• Non-PRASA systems delivered 7.04 Mgal/d to 101,627 people — about 69 gallons a day per person.
• 37,997 people drew their own groundwater, about 2.41 Mgal/d.

Agriculture (irrigation and livestock): 45.96 Mgal/d. Groundwater, mostly from the South Coastal Alluvial Plain aquifers, supplied 27.99 (22.42 irrigation, 5.57 livestock); surface water 17.97 (15.73 and 2.24), all from public irrigation districts run by the Puerto Rico Electric Power Authority on the south and northwest coasts. This water served 6.88 million animals, including poultry.

Industry, commerce and mining — manufacturing, hotels, restaurants, offices, civilian and military installations, sand and gravel: 56.20 Mgal/d (5.91 self-supplied, 50.29 from public supply).

Thermoelectric power (fossil fuels): 3.44 Mgal/d of freshwater (1.67 self-supplied, 1.77 public supply). Most of the water power plants use is seawater, not counted here.

Other PRASA uses — public housing, nonprofits, filter backwashing, water sold to cruise ships: 152.76 Mgal/d.

Unaccounted use — firefighting, street washing, parks, plus leaks, evaporation, unmetered deliveries, accounting errors and unauthorized use: 267.04 Mgal/d, mostly from public supply.

Source, use and disposition of freshwater in Puerto Rico, 2010, in million gallons per day. USGS.

Where the water ended up

A consumptive-use coefficient is the share of water used up — evaporated, transpired by plants, built into crops or consumed by people or animals — out of what was withdrawn or delivered. A return-flow coefficient is the share returned to the environment.

• Domestic, PRASA: 45 percent consumed, higher than non-PRASA and self-supplied domestic water (35 percent each), because PRASA deliveries include more outdoor use.
• Agriculture: 100 percent consumed. Puerto Rico has one of the highest evapotranspiration rates in the United States, about 45 inches a year.
• Thermoelectric: 25 percent, the lowest.
• There are no published local data on these coefficients, but the values fall within ranges found for the Great Lakes Basin and climatically similar areas.

Totals for 2010

Domestic use made up 30 percent of public-supply deliveries, and 61 percent of agricultural water came from aquifers.

Sources

Based on "Source, Use, and Disposition of Freshwater in Puerto Rico, 2010," U.S. Geological Survey fact sheet, summarizing W.L. Molina-Rivera, Estimated Water Use in Puerto Rico, 2010 (USGS Open-File Report); a work of the United States government in the public domain. The map and flow diagram are taken from the fact sheet's PDF.