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66°52'30" 66°52'00" 66°51'30"

18°06'30"

18°06'00"

18°05'30"

Lambert conformal conic projection

North American Datum of 1983 

0 0.1 0.2 0.3 0.4 0.5 KILOMETER

EXPLANATION

Reservoir bottom contour—Depth of the reservoir bottom, 

 in meters below spillway elevation of 173.74 meters

 above mean sea level, September 2013–May 2014.

 Contour interval 1 meter. 

Shoreline—Equal to zero depth

0 0.1 0.2 0.3 MILE

Figure 2. Bathymetric map of Lago Luccetti, Puerto Rico, September 2013--May 2014

RíoYauco branch

Rio Naraanjo branch

Quebrada Grande branch

Western branch

5

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3364

Sheet 1 of 1

Prepared in cooperation with the

Puerto Rico Aqueduct and Sewer Authority

Sedimentation Survey of Lago Lucchetti, Yauco, Puerto Rico, September 2013–May 2014

By

Julieta Gómez-Fragoso

2016

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Earth, its natural and living resources, natural hazards, and the environment—

visit http://www.usgs.gov or call 1–888–ASK–USGS.

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publications, visit http://store.usgs.gov/.

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government

Suggested citation: Gómez-Fragoso, Julieta, 2016, Sedimentation survey of Lago 

Lucchetti, Yauco, Puerto Rico, September 2013–May 2014: U.S. Geological Survey 

Scientific Investigations Map 3364, 1 sheet, http://dx.doi.org/10.3133/sim3364.

Abstract

The U.S. Geological Survey conducted a sedimentation survey of Lago Lucchetti, Yauco, Puerto Rico, 

in 2013–14 in cooperation with the Puerto Rico Aqueduct and Sewer Authority. The survey updated a previous 

survey, conducted in 2000, and provided accurate information regarding reservoir storage capacity and sedimentation rate using bathymetric techniques and a global positioning system coupled with a depth sounder device. The 

results of the 2013–14 survey indicated a total storage capacity for Lago Lucchetti of 10.21 million cubic meters 

and a long-term sedimentation rate loss of 0.16 million cubic meters per year based on the original capacity in 

1952. Sediment accumulation was about 10.14 million cubic meters over the life of the reservoir, which represents 

a storage decrease of about 50 percent of the original capacity in 1952. On the basis of a comparison between the 

2013–14 and 2000 surveys, the useful life for Lago Lucchetti is projected to end in 2076. 

Introduction

Lago Lucchetti is located at Yauco, Puerto Rico, and is part of the Southwestern Puerto Rico Project directed 

by the Puerto Rico Electric Power Authority (formerly named Puerto Rico Water Resources Authority). The 

project includes six reservoirs originally constructed for hydroelectric power generation and for irrigation of 

croplands in the southwest part of Puerto Rico. The original (1952) design capacity for Lago Lucchetti at the 

spillway elevation of 173.74 meters (m) above mean sea level (msl) was about 20.35 million cubic meters (Mm3). 

Over time, the actual capacity decreased to 15.84 Mm3 by 1986 and to 11.88 Mm3 by 2000 (Soler-López, 2001). 

The dam is located on the Río Yauco about 7 kilometers (km) north of the town of Yauco and 10 km east of the 

town of Sabana Grande (fig. 1). The dam is a concrete-gravity structure, and the reservoir has a drainage area of 

about 44.81 square kilometers. The outlet structure includes an uncontrolled spillway with a maximum discharge 

capacity of 1,778 cubic meters per second (m3/s) at a design head of 6.10 m above the spillway elevation and 

an intake for a 3,368-m-long and 3.50-m-diameter power tunnel that conveys water to two hydropower units 

(Soler-López, 2001) through a 2.44-m-diameter penstock.

Lago Lucchetti is owned and operated by the Puerto Rico Electric Power Authority for power generation and 

irrigation; however, since the late 1990s the reservoir also has been used as a source for public water supply to 

sustain local and regional water demands. As a result, Lago Lucchetti releases water through inter-basin transfers 

to Lago Loco (fig. 1), which in turn releases water for irrigation and public water supply. 

Between September 2013 and May 2014, the U.S Geological Survey (USGS) conducted a sedimentation 

survey (hereafter referred to as “the 2014 survey”) of Lago Lucchetti in cooperation with the Puerto Rico 

Aqueduct and Sewer Authority (PRASA) to update estimates of the reservoir storage capacity, determine the 

reservoir sedimentation rate, and estimate the amount and location of sediment accumulation. The results of the 

2014 survey were used to create a bathymetric map showing the reservoir bottom referenced to the spillway 

elevation. Results of the 2014 survey were also compared with data obtained during a previous survey in 2000 

(Soler-López, 2001).

Method of Survey and Analysis 

The field techniques and survey data processing methods used for the 2014 bathymetric survey were 

completed following procedures established by the USGS Caribbean-Florida Water Science Center (CFWSC) and 

described in a report by Soler-López (2001). The 2014 survey was conducted using a bathymetric survey system 

manufactured by Teledyne Odom Hydrographics, consisting of a global positioning system (GPS) coupled to a 

digital depth sounder. A total of 111 survey navigation lines were established at approximately 50-m intervals, 

beginning at the dam and continuing upstream along the main pool of the reservoir and its tributaries. Geographic 

position (accuracy of less than 2 m) and water depths (accuracy of 2 centimeters [cm] ±1 percent of the measured 

depth) were acquired simultaneously using the GPS interfaced with the depth sounder. The reservoir pool 

elevation was recorded continuously at USGS lake-level station 50125780 (Lago Lucchetti at Damsite near 

Yauco; fig. 1). The fathometer was calibrated prior to each day of the survey by using a bar check (Wilson and 

Richards, 2006).

The pool elevation of Lago Lucchetti was corrected to represent depths at a spillway elevation of 173.74 m 

above msl. The survey data were transferred into the Esri ArcGIS geographic information system (GIS); final 

analysis and storage volume calculations were made following procedures similar to those used to develop 

the February 2000 bathymetric map of Lago Lucchetti (Soler-López, 2001). Data points collected along each 

established navigation line (fig. 2) from the 2014 survey were used to generate a bathymetric map representing the 

reservoir bottom (fig. 3). Data points were color-coded according to their specific depths, and same-color points 

were connected with a line to draw depth contours (fig. 3). A triangulated irregular network (TIN) surface model 

of Lago Lucchetti was generated from the bathymetric map, and the reservoir volume was calculated using the 

GIS. The 2000 and 2013 –14 TIN surface models were used to compare the 2000 and 2014 sedimentation surveys 

(table 1) and to generate a stage-storage curve for 2014 (fig. 4) and longitudinal profiles along the main pool and 

tributaries of Lago Lucchetti for 2000 and 2013–14 (fig. 5). The storage capacity table and curve were generated 

by calculating the TIN volume at 1.00-m elevation intervals and are shown in table 2 and figure 4, respectively. 

Storage Capacity, Sedimentation Rate, and Useful Life

The Lago Lucchetti was built in 1952 with a storage capacity of 20.35 Mm3. The storage capacity progressively 

decreased from 15.84 Mm3 in 1986, to 11.88 Mm3 in 2000 (Soler-López, 2001), and to 10.21 Mm3 by the 2014 survey.

From the construction of the reservoir in 1952 until the 2014 survey, the storage capacity loss of the reservoir 

has been 10.14 Mm3, which is equivalent to a storage loss of about 50 percent. The long-term sedimentation rate 

(1952–2014) was about 0.16 million cubic meters per year (Mm3/yr), which is slightly less than the rate calculated 

during the 2000 survey (about 0.18 Mm3/yr; Soler-López, 2001). However, the inter-survey (2000–14) annual 

storage capacity loss was about 0.12 Mm3/yr, which is about 57 percent lower than the loss of about 0.28 Mm3/yr 

determined for 1986–2000. This sediment rate reduction could be the result of the decline in urban development and 

associated sediment runoff in the drainage basin of the reservoir. Another contributing factor could be lower rainfall 

and associated runoff from a decreased frequency and intensity of storm systems affecting the island of Puerto Rico 

in the last decade. Similar trends were observed after Hurricane Georges in 1998 at four other surveyed reservoirs 

in Puerto Rico: Lago Patillas, Lago de Cidra, Lago Loíza, and Lago Dos Bocas (Soler-López, 2010a, 2010b; 2012; 

Soler-López and Licha-Soler, 2012). The general results of the 2000 and 2014 surveys are summarized in table 1.

Table 1. Comparison of the 2000 and 2014 sedimentation surveys of Lago Lucchetti, Yauco, Puerto Rico.

[N/A, not applicable]

Data descriptor Year of survey

2000 2014

Total capacity, in million cubic meters 11.88 10.21

Reservoir surface area, in square kilometers 1.12 1.00

Reservoir surface area difference, in square kilometers N/A 0.12

Reservoir surface area loss, in percent N/A 11

Years since construction 48 62

Sediment accumulation since 1952, in million cubic meters 8.47 10.14

Inter-survey (2000 –14) sediment accumulation, in million cubic meters 13.96 1.67

Long-term (since 1952) storage loss, in percent 42 50

Long-term (since 1952) annual loss of capacity, in million cubic meters per year 0.18 0.16

Annual loss of capacity, in percent 0.9 0.8

Inter-survey (2000 –14) loss of capacity, in million cubic meters per year 0.28 0.12

Sediment trapping efficiency, in percent2 96 95

Long-term sediment yield, in cubic meters per square kilometer per year3 1,255 1,175

Inter-survey (2000 –14) sediment yield, in cubic meters per square kilometer per year3 12,013 858

Estimated year the reservoir is expected to fill with sediments4 2066 2076

1

Period between 1986 and 2000 surveys.

2

Using the capacity/inflow ratio described by Brune (1953).

3

Using the combined drainage area of Lago Guayo, Lago Prieto, and Lago Yahuecas and assuming a dry-bulk density of sediments

of 1 gram per cubic centimeter. 

4

Assuming that the reservoir would continue to fill at the average long-term sedimentation rate.

Pool elevation,

in meters 

above mean

sea level

Storage capacity, 

in million cubic 

meters

173.74 10.21

172.74 9.29

171.74 8.44

170.74 7.65

169.74 6.92

168.74 6.23

167.74 5.59

166.74 5.05

Table 2. Storage capacity at 1-meter intervals from spillway elevation for Lago Lucchetti, Yauco, Puerto Rico, 2014.

Pool elevation,

in meters 

above mean

sea level

Storage capacity, 

in million cubic 

meters

165.74 4.55

164.74 4.07

163.74 3.62

162.74 3.19

161.74 2.79

160.74 2.41

159.74 2.05

158.74 1.71

The bottom profiles (fig. 5) along the central part of Lago Lucchetti were generated in an upstream direction 

from the dam to each of the tributaries of the reservoir (Río Yauco, Western, Río Naranjo, and Quebrada Grande). 

The results show that most of the sediment accumulation and associated storage capacity loss of Lago Lucchetti has 

occurred on the Río Yauco and Quebrada Grande tributaries of the reservoir. For Río Yauco, the most noticeable 

sediment accumulation zone is about 1,300 m upstream from the dam; sediment accumulation ranges from 2 to 4 m 

(fig. 5A) and extends to the mouth where it enters the reservoir. The sediment accumulation between 2000 and 2014 

in the Quebrada Grande ranged from 2 to 4 m, and sediment was distributed along the entire reservoir bottom profile 

(fig. 3D). For Río Naranjo and Western tributaries, the sedimentation accumulation is mostly distributed near the 

dam structure and ranges from 0.5 to 2 m. 

Comparison of bottom profiles along Río Yauco, Western, and Río Naranjo indicated that substantial sediment 

deposition occurs in an area about 450 m upstream from the dam structure (fig. 5). As described by Soler-López 

(2001), deposition of sediments, caused by flood events, may have occurred in the confluence of the reservoir and its 

tributaries. The 2014 survey results indicate the sediment accumulation has continued in this area over the years. 

Using the empirical-based curve developed by Brune (1953), the sediment trapping efficiency of Lago Lucchetti

for 2014 was estimated as 95 percent. This method used the ratio of storage capacity to annual water inflow volume, 

in which the annual inflow was estimated at 25.95 Mm3 (Soler-López, 2001) and the updated 2014 water storage 

capacity was about 10.21 Mm3. Updated precipitation depth was incorporated in the 2014 study for the annual 

inflow calculations by using the mean annual precipitation for the period 1981 to 2010 (National Oceanic and 

Atmospheric Administration, 2010).

The long-term drainage area sediment yield rate of Lago Lucchetti was 1,175 cubic meters per square kilometer 

per year ([m3/km2]/yr) in the 2014 survey. This sediment yield rate represents a decrease of 6 percent compared to 

the 2000 survey, which had a sediment yield rate of 1,255 (m3/km2)/yr. Inter-survey drainage area sediment yield in 

turn decreased from 2,013 (m3/km2)/yr in 2000 to 858 (m3/km2)/yr in 2014.

On the basis of the current long-term storage-capacity loss of about 0.16 Mm3/yr estimated for the 1952–2014 

period and assuming a constant sedimentation rate, the projected useful life of Lago Lucchetti is about 62 years, 

ending in 2076. This predicted useful life (also referred as the year of zero storage) of Lago Lucchetti is nearly equal 

to the previous estimate of 66 years of useful life calculated by Soler-López (2001). Data release of spatial data 

associated with the 2014 bathymetric survey is presented in Gómez-Fragoso, 2016.

Conclusions 

A sedimentation survey was conducted at the Lago Lucchetti, Yauco, Puerto Rico, by the U.S. Geological Survey

in cooperation with the Puerto Rico Aqueduct and Sewer Authority during September 2013 and May 2014. The 

objective of the project was to complete a bathymetric study to update the reservoir storage capacity and estimate 

the reservoir sedimentation rate by comparing the new survey data with a previous survey completed in 2000. 

The Lago Lucchetti storage capacity decreased from 11.88 Mm3 in March 2000 to 10.21 Mm3 in May 2014. 

The survey results show a long-term storage capacity loss of about 50 percent, corresponding to a decrease of about 

0.16 Mm3/yr since the reservoir was built in 1952. Comparison of the 2014 results with a previous sedimentation 

survey in 2000 indicated that on a long-term basis, the sedimentation rate remained relatively constant. The intersurvey sediment accumulation was 1.67 Mm3

 between 2000 and 2014; this represents a reservoir sedimentation loss 

of about 0.12 Mm3/yr between 2000 and 2014. 

Most of the sediment accumulation and associated storage capacity loss of Lago Lucchetti has occurred along 

the Río Yauco and Quebrada Grande tributaries of the reservoir. Sediment deposition and scour were observed in 

2014 in the vicinity of the dam compared to the 2000 survey.

The Lago Lucchetti drainage area sediment yield has decreased by about 6 percent, from 1,255 (m3/km2)/yr 

based on 2000 survey to 1,175 (m3/km2)/yr based on 2014 survey. If the long-term sedimentation rate of 0.16 Mm3/yr 

remains constant, loss of storage capacity will most likely end the useful life of Lago Lucchetti by 2076.

Acknowledgments

The author thanks colleagues in the USGS Caribbean-Florida Water Science Center in San Juan, Puerto Rico, 

who provided support for the completion of this study. Special recognition is given to Luis Soler who participated 

during field data collection. The author also thanks Marilyn Santiago who provided assistance during the preparation 

of the data release of spatial data associated with this study. 

References Cited

Brune, G.M., 1953, Trapping efficiency of reservoirs: Transactions of the American Geophysical Union, v. 34,

no. 3, p. 407– 418.

Gómez-Fragoso, Julieta, 2016, Spatial data for the sedimentation survey of Lago Lucchetti, Yauco, Puerto Rico, 

September 2013–May 2014: U.S. Geological Survey data release, accessed August 22, 2016, http://dx.doi.org/

10.5066/F7V122WZ.

National Oceanic and Atmospheric Administration (NOAA), 2010, Mean annual rainfall 1981–2010 for Puerto Rico 

and U.S. Virgin Islands, accessed June 2016 at http://www.srh.noaa.gov/sju/?n=mean_annual_precipitation2. 

Soler-López, L.R., 2001, Sedimentation survey of Lago Lucchetti, Puerto Rico, March 2000: U.S. Geological Survey

Water-Resources Investigations Report 2001–4105.

Soler-López, L.R., 2010a, Sedimentation survey of Lago de Cidra, Puerto Rico, August 2007: U.S. Geological Survey

Scientific Investigations Map 3118, 1 sheet. [Also available at http://pubs.usgs.gov/sim/3118/.]

Soler-López, L.R., 2010b, Sedimentation survey of Lago Patillas, Puerto Rico, March 2007: U.S. Geological Survey 

Scientific Investigations Map 3128, 1 sheet. [Also available at http://pubs.usgs.gov/sim/3128/.]

Soler-López, L.R., 2012, Sedimentation survey of Lago Dos Bocas, Utuado, Puerto Rico, January 2010: U.S. 

Geological Survey Scientific Investigations Map 3217, 1 sheet. [Also available at http://pubs.usgs.gov/sim/3217/.]

Soler-López, L.R., and Licha-Soler, N.A., 2012, Sedimentation survey of Lago Loíza, Puerto Rico, July 2009: U.S. 

Geological Survey Scientific Investigations Map 3219, 1 sheet. [Also available at http://pubs.usgs.gov/sim/3219/.]

Wilson, G.L., and Richards, J.M., 2006, Procedural documentation and accuracy assessment of bathymetric maps 

and area/capacity tables for small reservoirs: U.S. Geological Survey Scientific Investigations Report 2006 –5208, 

24 p. [Also available at http://pubs.usgs.gov/sir/2006/5208.]

Figure 3. Bathymetric map of Lago Luccetti, Puerto Rico, September 2013–May 2014.

66°52'30"

18°06'30"

18°06'00"

18°05'30"

18°05'00"

Image from U.S. Army Corps of Engineers 2010 orphophotos

Figure 3. Location of points where bathymetric data were collected.

66°52'00" 66°51'30"

0 0.25 0.5 0.75 1 KILOMETER

0 0.25 0.5 MILE Point where bathymetric data were collected

EXPLANATION

50125780

Yauco

Sabana

Grande

Guayanilla

Guánica

66°55' 66°50'

18°10'

18°05'

18°00'

17°55'

Río Yauco Basin

Map area

Figure 1. Location of Lago Lucchetti, Yauco, Puerto Rico

PUERTO RICO

Lago 

Lucchetti

Lago

Guayo

Lago

Loco

Lago

Prieto

Lago

Toro

Rio

Yauco

Western

branch 

Quebrada

Grande

branch 

Rio Naranjo branch

Río Yauco

branch

Inter-basin diversion

EXPLANATION

USGS lake station with number

Base modified from U.S. Geological Survey

1:20,000-scale digital data for Puerto Rico

0 2.5 5 KILOMETERS

0 1 2 MILES

Figure 1. Location of Lago Lucchetti, Yauco, Puerto Rico.

Figure 2. Location of points where bathymetric data were collected.

145 

150 

155 

160 

165 

170 

175 

0 2 4 6 8 10 12 

Pool elevation, in meters above mean sea level 

Storage volume in million cubic meters 

2014 

Spillway elevation 173.74 meters

Figure 4. Pool elevation and storage volume for the Lago Lucchetti , Yauco, Puerto Rico (survey 2014).

0 

5 

10 

15 

20 

25 

30 

2000 

2014 

A

B

C

D

0 

5 

10 

15 

20 

25 

30 

Depth, in meters below spillway elevation of 173.74 meters above mean sea level 

0 

5 

10 

15 

20 

25 

30 

0 

5 

10 

15 

20 

25 

30 

0 500 1,000 1,500 2,000 2,500 3,000 3,500 

Distance from dam, in meters 

Figure 5. Longitudinal bottom profiles for 2000 and 2014 along the A, Rio Yauco; B, Western; C, Rio Naranjo; 

and D, Quebrada Grande tributaries of Lago Lucchetti, Yauco, Puerto Rico.

Pool elevation,

in meters 

above mean

sea level

Storage capacity, 

in million cubic 

meters

157.74 1.39

156.74 1.10

155.74 0.84

154.74 0.60

153.74 0.39

152.74 0.20

151.74 0.08

150.74 0.01

149.74 0.00