U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3080

September 2009

Prepared in cooperation with the Puerto Rico Aqueducts and Sewers Authority, Puerto Rico Department of Natural and Environmental 

Resources, and Puerto Rico Environmental Quality Board 

Source, Use, and Disposition of Freshwater

in Puerto Rico, 2005

Printed on recycled paper

Introduction

Water diverted from streams and pumped from wells 

constitutes the main sources of water for the 78 municipios 

of the Commonwealth of Puerto Rico (fig. 1). A better 

understanding is needed about water-use patterns, particularly 

about the amount of water used, where and how this water 

is used and disposed, and how human activities impact 

water resources. Irrigation practices, indoor and outdoor 

household uses, industrial uses, and commercial and mining 

withdrawals affect reservoirs, streams, and aquifers. Accurate 

and accessible water information for Puerto Rico is critical 

to ensure that water managers have the ability to protect and 

conserve this natural resource. 

The population of Puerto Rico increased 15 percent, from 

3.4 million in 1985 to 3.9 million people 2005 and resulted 

in an increased demand for freshwater, mostly for the publicsupply water use category. Almost 99 percent of the residents 

in Puerto Rico were served by public-supply water systems 

in 2005. One of the major challenges that water managers 

confront is the need to provide sufficient freshwater availability 

in the densely populated areas. Public-supply water is provided 

by the Puerto Rico Aqueducts and Sewers Authority (PRASA) 

and by non-PRASA systems. Non-PRASA systems refer to 

community-operated water systems (water systems that serve 

a rural or suburban housing area). 

Sources of Water

Water-use data and concepts presented in this factsheet 

refer only to offstream uses. Offstream use is the freshwater 

diverted or withdrawn from a surface -water or groundwater 

source and conveyed to the place of use. Offstream use is 

sometimes referred to as withdrawal use. Instream use refers 

to water that is used, but not withdrawn, from ground or 

surface- water sources for such purposes as thermoelectricsaline withdrawals and hydroelectric power.

In 2005, a total of 722 million gallons per day (Mgal/d) 

of freshwater was processed in Puerto Rico to satisfy the 

demand of approximately 3.9 million of people (U.S. Census 

Bureau, 2006). Puerto Rico has only three main natural 

sources of freshwater: groundwater, surface water, and 

desalinated water. Because desalinated water represents less 

than 1 percent of the total freshwater withdrawals, it is not 

considered in this analysis. For the purpose of this factsheet, 

public-supply water is a freshwater source. 

Figure 1. Location of municipios and the South Coastal Alluvial Plain aquifer system in Puerto Rico.
Figure 2. Source, use, and disposition of freshwater in Puerto Rico, in million gallons per day, 2005.
Groundwater sources provided about 146.9 Mgal/d (GW 

in box A, fig. 2) or 20 percent of the total freshwater withdrawn 

in Puerto Rico during 2005. About 96.2 Mgal/d (PS subtotal in 

box A1, fig. 2) or 65 percent were produced by public-supply 

water wells and 50.7 Mgal/d or 35 percent were obtained from 

self-supplied withdrawals. 

Surface-water sources provided about 575.1 Mgal/d (SW 

in box B, fig. 2) or 80 percent of the total freshwater withdrawn 

in Puerto Rico during 2005. About 556.3 Mgal/d (PS subtotal 

in box B1, fig. 2) or 97 percent were produced by public-supply 

water facilities; the remaining 18.8 Mgal/d or 3 percent were 

self-supplied withdrawals. 

Use of Water

Offstream use accounted for four major water-use 

categories: (1) domestic use (self-supplied withdrawals, nonPRASA and PRASA public-supply deliveries) represented as 

DOM-SS, DOM-NPR, DOM-PR in figure 2; (2) agriculture 

use (irrigation and livestock) represented as AIL in figure 2, (3) 

industrial use (commercial and mining) represented as ICM in 

figure 2, and (4) thermoelectric power use represented as T in 

figure 2. Public uses and conveyance losses were considered to 

be an unaccounted use and are represented as UNACC in 

figure 2.

Domestic Use (Self-Supplied Withdrawals and Non-PRASA and 

PRASA Public-Supply Deliveries)

Domestic use includes water used for indoor and outdoor 

household purposes, such as drinking, preparing food, 

bathing, washing clothes and dishes, flushing toilets, cleaning 

vehicles, and maintaining lawns and gardens. The domestic 

use combines the amount of water that is withdrawn by selfsupplied systems, in addition to the water that is delivered from 

public-supply water systems (non-PRASA and PRASA).

During 2005, the domestic self-supplied withdrawals 

were estimated at 2.10 Mgal/d (DOM-SS in box 13, fig. 2) 

to serve a population of 30,722 people, where groundwater 

was the only source of domestic self-supplied withdrawals. 

In addition the PRASA delivered 346.8 Mgal/d (DOM-PR 

in box 14, fig. 2) for domestic use to serve a population of 

3.79 million inhabitants. Groundwater sources delivered 69.4 

Mgal/d (DOM-PR in box 2, fig. 2) and surface-water sources 

delivered 277.4 Mgal/d (DOM-PR in box 8, fig. 2). On this 

basis, domestic per capita use was estimated at 92 gallons per 

day per person (gal/d-p). The non-PRASA systems provided 

5.9 Mgal/d (DOM-NPR in box 14, fig. 2) to serve a population 

of about 86,492 people, thus estimating a domestic per capita 

use of 68 gal/d-p. Groundwater sources were estimated at 3.2 

Mgal/d (DOM-NPR in box 2, fig. 2) and surface-water sources 

were estimated at 2.7 Mgal/d (DOM-NPR in box 8, fig. 2). 

Agricultural Use (Irrigation and Livestock)

Agricultural use includes the water applied for irrigation 

purposes and for livestock practices. The quantity of water 

withdrawn for agricultural use (irrigation and livestock) during 

2005 was estimated at 52.9 Mgal/d (AIL in box 13, fig. 2), 

whereas 35.7 Mgal/d (AIL in box 1, fig. 2) were withdrawn for 

irrigation and livestock activities from groundwater sources. 

Surface water provided 17.2 Mgal/d (AIL in box 7, fig. 2) 

for these activities. Groundwater and surface water from 

self-supplied sources satisfied the water requirements of 11.6 

million animals (including poultry) in Puerto Rico during 2005 

(U.S. Department of Agriculture, 2003). 

Groundwater sources provided 30.01 Mgal/d for irrigation 

and 5.71 Mgal/d for livestock to total 35.7 Mgal/d (AIL in box 

1, fig. 2), or 67 percent of the total freshwater withdrawn for 

agricultural use, mostly from the South Coastal Alluvial Plain 

aquifer system (fig. 1). Surface-water sources provided 15.15 

Mgal/d for irrigation and 2.08 Mgal/d for livestock to total 17.2 

Mgal/d (AIL in box 7, fig. 2), or 32 percent of the total water 

withdrawn. All of the surface-water withdrawn was provided 

by public irrigation districts, which are irrigation systems 

operated by the Puerto Rico Electric and Power Authority 

(PREPA), located in the southern and northwestern coasts of 

Puerto Rico. All reported irrigation withdrawals are identified 

as self-supplied although they were diverted from a public 

irrigation district. 

Industrial Use (Commercial and Mining)

The combined industrial use category included the 

withdrawals for industries, commercial businesses, and mining 

facilities. Industrial use includes water used for manufacturing 

processes, such as fabrication, processing, washing, and 

cooling. Commercial use includes water used by hotels, 

restaurants, office buildings, commercial facilities, and civilian 

and military institutions. Mining use includes water used for 

the extraction of sand and gravel. 

Total combined industrial use during 2005 was estimated 

at 111.6 Mgal/d (ICM in box 15, fig. 2). Self-supplied 

withdrawals accounted for 11.7 Mgal/d (ICM in box 13, fig. 

2) or 10 percent of the total water withdrawn and delivered 

for the combined industrial use. The main source of the selfsupplied withdrawals for industrial use was groundwater. The 

remaining 99.9 Mgal/d (ICM in box 14, fig. 2) or 90 percent of 

the water used for industrial, commercial, and mining activities 

was from public-supply deliveries.

Thermoelectric Power Water Use

The thermoelectric power category includes water 

used in the generation of electric power with fossil-fuel 

energy. Although the largest amount of water used by the 

thermoelectric power facilities was from seawater sources, this 

amount was not considered in this factsheet because the salinewater withdrawal is considered an instream use. Freshwater 

withdrawals accounted for 5.1 Mgal/d (T in box 15, fig. 2), of 

which self-supplied withdrawals accounted for 2.8 Mgal/d (T in 

box 13, fig. 2), and the remaining 2.3 Mgal/d (T in box 14, fig. 

2) was from public-supply deliveries.

Unaccounted Use (Public Water Use and Conveyance Losses)

The unaccounted water use combines the public-water 

use and the conveyance losses. Public-water use includes 

water used for non-individual consumption activities such 

as firefighting, street washing, and recreational activities at 

municipal parks. A conveyance loss is the term used for water 

that is lost while in transit from a pipe or canal system due to 
leakage or evaporation. Water that is lost due to groundwater 

leakage and/or percolates to an aquifer can become available 

and can be considered a return flow. This fact sheet includes 

the conveyance losses where water was lost while in transit 

from a pipe or canal system. An apparent loss is the term used 

for water that is delivered to customers but is not metered. 

This loss can occur due to unmetered systems, errors in water 

accounting, and unauthorized use of water. 

Public-water use and conveyance losses accounted 

for 197.5 Mgal/d (UNACC in box 15, fig. 2) during 2005. 

Groundwater was the source for 11.6 Mgal/d (UNACC in box 

3, fig. 2) delivered by public-water supply systems and 185.9 

Mgal/d (UNACC in box 9, fig. 2) was delivered from surface 

water systems. Forty-five percent or 88.9 Mgal/d (UNACC 

in box 16, fig. 2) of the total unaccounted use was consumed. 

About 6 percent or 11.8 Mgal/d (UNACC in box 17, fig. 2) was 

returned to the environment through underground leakage and/

or percolation into an aquifer. The remaining 49 percent or 96.8 

Mgal/d (UNACC in box 18, fig. 2) was lost or removed from 

the environment and is unavailable for further use. 

Disposition of Water

The disposition columns in figure 2 show the proportion 

of water consumed (consumptive use) and the water that 

is returned to the environment (return flows). A specific 

consumptive use was estimated for each category by applying a 

coefficient. Table 1 contains the estimated consumptive use for 

Puerto Rico by source and category during 2005. 

The consumptive use for each category was calculated 

applying the following equation:

Consumptive Use in Mgal/d= (Withdrawals + Deliveries) 

x Consumptive-Use Coefficient 

Consumptive-use coefficients were applied based on 

previous water-use compilations (Solley and others, 1998). For 

example, consumptive use for domestic public-supply water 

PRASA (Domestic PRASA in table 1) was estimated as 45 

percent, 10 percent more than in domestic public-supply water 

non-PRASA and domestic self-supplied that was estimated at 

35 percent. This difference exists because the people that are 

served from domestic public-supply water systems have an 

elevated per capita use (92 gal/d-p) and consequently, a higher 

consumptive use rate (45 percent of total withdrawals and 

deliveries). 

The consumptive-use coefficient for agricultural use 

(irrigation and livestock) was 100 percent (table 1). Puerto 

Rico has the highest estimated mean evapotranspiration in the 

United States (45 inches per year) (Hanson, 1991); therefore, 

all of the water withdrawn for agricultural activities in Puerto 

Rico was considered to be consumed and return flows were not 

accounted for in this category.

Water returned to the environment was calculated applying 

a return flow coefficient. The following equation was applied 

to calculate the water return to the environment:

Water returned to environment in Mgal/d = 

(Withdrawals + Deliveries) x Return Flow Coefficient 

The total freshwater withdrawn and delivered during 

2005 was 341.4 Mgal/d or 47 percent for consumptive use. 

An estimated 283.8 Mgal/d or 39 percent was returned to the 

environment, mainly through wastewater treatment plants. The 

remaining 96.8 Mgal/d or 13 percent was unaccounted use that 

was lost and not returned to the environment for further use 

(fig. 2). 

Reference Cited

Hanson, R.L., 1991, Evapotranspiration and droughts, in 

Paulson, R.W., Chase, E.B., Roberts, R.S., and Moody, D.W., 

Compilers, National Water Summary 1988-89—Hydrologic 

Events and Floods and Droughts: U.S. Geological Survey 

Water-Supply Paper 2375, p. 99-104: accessed June 2009 at 

http://geochange.er.usgs.gov/sw/change/natural/et

Molina-Rivera, W.L., and Gómez-Gómez, F., 2008, Estimated 

water use in Puerto Rico, 2005: U.S. Geological Survey 

Open-file report 2008-1286, 37 p.: accessed August 2009 at 

http://pubs.usgs.gov/of/2008/1286/

Solley, W.B., Pierce, R.R., and Perlman, H.A., 1998, Estimated 

use of water in the United States in 1995: U.S. Geological 

Survey Circular 1200, 71 p.

U.S. Census Bureau, 2006, Population Division, Annual 

Estimates of the population for municipios of Puerto Rico: 

April, 2000 to July 1, 2005 (PRM-EST 2005-01).

U.S. Department of Agriculture, 2003, 2002 Census of 

Agriculture, Puerto Rico municipio profiles: accessed 

August 2004 at www.nass.usda.gov/census/census02/ 

puertorico/profiles/index.htm

Water-use categories Consumptive-use coefficient by source of water (in percent)

Groundwater Surface water

Domestic (self-supplied and non-PRASA) 35 35

Domestic (PRASA) 45 45

Agriculture (irrigation and livestock) 100 100

Industrial (commercial and mining) 29 37

Thermoelectric 25 25

[PRASA, Puerto Rico Aqueducts and Sewers Authority]

Table 1. Estimated consumptive use coefficient for Puerto Rico, 2005.
Puerto Rico 2005 Water – Use Facts

• Offstream uses totaled 722 million gallons per day.

• Surface water provided 575 million gallons per day, or 80 percent, and groundwater provided 147 million gallons per day, or 20 

percent, of the total offstream water used in Puerto Rico.

• The average amount of domestic water used per person per day was 92 gallons.

• A total of 45 percent of the water produced for domestic use by public-supply water systems was consumed. 

• Irrigation water use was estimated as 45 million gallons per day with 66 percent obtained from aquifers.

• The mean annual evapotranspiration rate for Puerto Rico was estimated as 45 inches per year. This is the highest evapotranspiration 

rate in the United States.

• All of the water (100 percent) used for agricultural purposes (irrigation and livestock) was consumed.

Question or request for additional data related to water 

use in Puerto Rico can be directed to the author:

Wanda L. Molina-Rivera

U.S. Geological Survey

GSA Center, bldg 651 Federal Drive, Suite 400-15

Guaynabo, P.R. 00965-5703

(787) 749-4346 ext. 259

wlmolina@usgs.gov

Additional information is available in 

the publication “Estimated Water Use in 

Puerto Rico, 2005” at http://pubs.usgs.gov/

of/2008/1286/

U.S. Department of the Interior

KEN SALAZAR, SECRETARY 

U.S. Geological Survey

Suzette M. Kimball, Acting Director