Simulation of Flow in the Upper North Coast Limestone 

Aquifer, Manatí-Vega Baja Area, Puerto Rico

Water-Resources Investigation Report 00-4266

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the

PUERTO RICO DEPARTMENT OF NATURAL AND ENVIRONMENTAL RESOURCES

and the PUERTO RICO INDUSTRIAL DEVELOPMENT CORPORATION
Cover photograph

Western portion of Laguna Tortuguero looking south. Photograph taken by Gregory S. Cherry, February 22, 2001.
U.S. Department of the Interior

U.S. Geological Survey

Simulation of Flow in the Upper North Coast Limestone 

Aquifer, Manatí-Vega Baja Area, Puerto Rico

By Gregory S. Cherry

Water-Resources Investigations Report 00-4266

In cooperation with the

PUERTO RICO DEPARTMENT OF NATURAL AND ENVIRONMENTAL RESOURCES

and the PUERTO RICO INDUSTRIAL DEVELOPMENT CORPORATION

San Juan, Puerto Rico: 2001
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

Use of trade names in this report is for identification purposes only and does not imply endorsement by the 

U.S. Government.

For additional information write to: Copies of this report can be purchased from:

District Chief

U.S. Geological Survey U.S. Geological Survey

GSA Center, Suite 400-15 Branch of Information Services

651 Federal Drive Box 25286

Guaynabo, Puerto Rico 00965 Denver, CO 80225
Contents III

CONTENTS

Abstract ................................................................................................................................................................ 1

Sumario ................................................................................................................................................................ 2

Introduction.......................................................................................................................................................... 4

Description of the Study Area ....................................................................................................................... 4

History of Water Use ..................................................................................................................................... 7

Acknowledgments ......................................................................................................................................... 9

Hydrogeologic Setting ......................................................................................................................................... 9

Geologic Setting ............................................................................................................................................ 10

Upper North Coast Limestone Aquifer ......................................................................................................... 18

Hydraulic Properties ............................................................................................................................... 18

Direction of Ground-Water Flow ............................................................................................................ 23

Hydraulic Connection with Surface-Water Features............................................................................... 23

Recharge.................................................................................................................................................. 26

Discharge to Springs ............................................................................................................................... 28

Confining Unit within the North Coast Limestone Aquifer System ............................................................. 28

Lower North Coast Limestone Aquifer ......................................................................................................... 28

Simulation of Ground-Water Flow in the Upper Aquifer .................................................................................... 28

Model Assumptions....................................................................................................................................... 30

Grid Design and Boundary Conditions ......................................................................................................... 32

Internal Boundaries........................................................................................................................................ 32

Simulated Recharge and Discharge ............................................................................................................... 34

Model Calibration Process............................................................................................................................. 39

Simulated Change at Laguna Tortuguero 1940 to 1995 ................................................................................ 40

Additional Calibration ................................................................................................................................... 40

Sensitivity Analysis ....................................................................................................................................... 44

Simulated Effects of Development ................................................................................................................ 47

Effect of Ground-Water Withdrawals on Hydrologic System ................................................................ 47

Projected Changes in Ground-Water Withdrawals ................................................................................. 47

Model Limitations and Additional Data Needs ................................................................................................... 49

Summary .............................................................................................................................................................. 49

Selected References ............................................................................................................................................. 52

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer.................................................... 57

Appendix 2a. Summary of sensitivity of ground-water recharge ........................................................................ 79

Appendix 2b. Summary of sensitivity analysis for simulated injection and pumping rates at wells................... 80

Appendix 2c. Summary of sensitivity analysis of aquifer transmissivity ............................................................ 81

Appendix 2d. Summary of sensitivity of riverbed conductance .......................................................................... 82
IV Contents

FIGURES

1.-3. Map showing:

1. Location of the Manatí-Vega Baja study area and important hydrologic features, North Coast 

Province, Puerto Rico........................................................................................................................ 5

 2. Selected land uses in 1977 and 1987 in the Manatí-Vega Baja study area, North Coast Province, 

Puerto Rico........................................................................................................................................ 6

 3. Average annual rainfall distribution and location of stream-gaging and precipitation stations in 

the Manatí-Vega Baja study area, North Coast Province, Puerto Rico ............................................. 8

 4. Graph showing historical and projected future use of ground water in the Manatí-Vega Baja study 

area, North Coast Province, Puerto Rico................................................................................................ 9

 5. Diagram showing stratigraphic nomenclature of the middle Tertiary sequence and hydrogeologic 

units of the North Coast Limestone aquifer system, Puerto Rico .......................................................... 10

6.-14. Map showing:

6. Location of wells, springs, and filtration plant in the Manatí-Vega Baja study area, North 

Coast Province, Puerto Rico.............................................................................................................. 11

7. Generalized surficial geology of the Manatí-Vega Baja study area and location of 

hydrogeologic cross sections, North Coast Province, Puerto Rico .................................................. 16

8. Generalized hydrogeologic cross sections of the North Coast Province, Puerto Rico ......................... 17

 9. Estimated altitude of the base of the upper aquifer in the Manatí-Vega Baja study area, North 

Coast Province, Puerto Rico.............................................................................................................. 19

10. Transmissivity distribution for the upper aquifer as estimated from well specific-capacity 

data, Manatí-Vega Baja study area, North Coast Province, Puerto Rico .......................................... 21

11. Transmissivity distribution for the upper aquifer as estimated using average hydraulic 

conductivity values for freshwater-saturated hydrogeologic units in the Manatí-Vega Baja 

study area, North Coast Province, Puerto Rico................................................................................. 22

12. Potentiometric surface of the upper aquifer during March 1995, Manatí, North Coast 

Province, Puerto Rico........................................................................................................................ 24

13. Location of surficial drainage areas along the southern boundary of the upper aquifer, 

North Coast Province, Puerto Rico ................................................................................................... 27

14. Areas for which digital ground-water flow models have been developed in the North Coast 

Limestone aquifer system, Puerto Rico............................................................................................. 29

15. Hydrograph of ground-water levels at well 105 (Cantito La Luisa), Manatí area, Puerto Rico................... 31

16. Map showing model grid and boundary conditions of the upper aquifer in the Manatí-Vega Baja 

study area, North Coast Province, Puerto Rico ...................................................................................... 33

17. Map showing calibrated recharge distribution used for the digital ground-water flow model 

simulations of the upper aquifer system in the Manatí-Vega Baja study area, North Coast 

Province, Puerto Rico ............................................................................................................................. 35

18. Graph showing ground-water withdrawal rates used for each stress period for the transient 

simulations, Manatí-Vega Baja model area, North Coast Province, Puerto Rico................................... 36
Contents V

19.-21. Map showing:

19. Calibrated transmissivity distribution for the digital ground-water flow model simulations 

of the upper aquifer in the Manatí-Vega Baja area, North Coast Province, Puerto Rico ................... 41

20. Simulated potentiometric surface for March 1995 steady-state conditions in the ManatíVega Baja study area, North Coast Province, Puerto Rico 42

21. Simulated potentiometric surface for 1940 steady-state conditions in the Manatí-Vega Baja 

study area, North Coast Province, Puerto Rico.................................................................................. 43

22. Graph showing comparison of measured and simulated discharge at Laguna Tortuguero 

outflow site .............................................................................................................................................. 44

23. Graph showing sensitivity of model to changes in transmissivity and recharge ........................................... 46

24. Map showing simulated potentiometric surface from transient model runs using 1995 hydrologic 

conditions and predicted conditions for 2010 in the Manatí-Vega Baja study area, North Coast 

Province, Puerto Rico.............................................................................................................................. 48

TABLES

1. Characteristics of well data-collection sites and location within the Manatí-Vega Baja ground-water 

model, North Coast Province, Puerto Rico ............................................................................................. 12

2. Ground-water withdrawal rates used for the Manatí-Vega Baja transient simulation for each stress 

period....................................................................................................................................................... 37

3. Comparison of simulated steady-state ground-water budgets for 1940 and March 1995 hydrologic 

conditions, Manatí-Vega Baja area, North Coast Province, Puerto Rico ................................................ 45
VI Contents

CONVERSION FACTORS, WATER-QUALITY UNIT, ACRONYMS, and TRANSLATIONS

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (°C x 1.8) + 32

Abbreviated water-quality unit used in this report:

mg/L milligrams per liter

Acronyms used in this report

NCCD North Coast Climatic Division

PRASA Puerto Rico Aqueduct and Sewer Authority

PRDNER Puerto Rico Department of Natural and Environmental Resources

USGS U.S. Geological Survey

Translations

Spanish English

caño channel or drainage ditch

de of

grande grand or large

el, los, la, las the

lago lake

laguna lagoon

municipio generally equivalent to county

norte north 

quebrada stream or creek

río river

sur south

Multiply By To obtain

cubic foot (ft3) 0.02832 cubic meter

cubic foot per second (ft3/s) 0.02832 cubic meter per second

foot (ft) 0.3048 meter

foot per day (ft/d) 0.3048 meter per day

foot squared per day (ft2/d) 0.0929 meter squared per day

inch (in.) 25.4 millimeter

mile (mi) 1.609 kilometer

million gallons per day (Mgal/d) 0.04381 cubic meter per second

million gallons per day (Mgal/d) 0.02832 million liters per day

square mile (mi2) 259.0 hectare

square mile (mi2) 2.590 square kilometer
Abstract 1

Abstract 

A two-dimensional computer ground-water 

model was constructed of the Manatí-Vega Baja 

area to improve the understanding of the 

unconfined upper aquifer within the North Coast 

Province of Puerto Rico. The modeled area covers 

approximately 79 square miles within the 

municipios of Manatí and Vega Baja and small 

portions of Vega Alta and Barceloneta. 

Steady-state two-dimensional ground-water 

simulations were correlated to conditions prior to 

construction of the Laguna Tortuguero outlet 

channel in 1940 and calibrated to the observed 

potentiometric surface in March 1995. At the 

regional scale, the unconfined Upper North Coast 

Limestone aquifer is a diffuse ground-water flow 

system through the Aguada and Aymamón 

limestone units. The calibrated model input 

parameters for aquifer recharge varied from 2 

inches per year in coastal areas to 18 inches per 

year in the upland areas south of Manatí and Vega 

Baja. The calibrated transmissivity values ranged 

from less than 500 feet squared per day in the 

upland areas near the southern boundary to 

70,000 feet squared per day in the areas west of 

Vega Baja. Increased ground-water withdrawals 

from 1.0 cubic foot per second for 1940 

conditions to 26.3 cubic feet per second in 1995, 

has reduced the natural ground-water discharge to 

springs and wetland areas, and induced additional 

recharge from the rivers. The most important 

regional drainage feature is Laguna Tortuguero, 

which is the major ground-water discharge body 

for the upper aquifer, and has a drainage area of 

approximately 17 square miles. The discharge to 

the sea from Laguna Tortuguero through the 

outlet channel has been measured on a bi-monthly 

basis since 1974. The outflow represents a 

combination of ground- and surface-water 

discharge over the drainage area.

Hydrologic conditions, prior to 

construction of the Laguna Tortuguero outlet 

channel in 1943, can be considered natural 

conditions with minimal ground-water pumpage 

(1.0 cubic foot per second), and heads in the 

lagoon were 2.4 feet higher. The model was 

calibrated to March 1995 conditions during a dry 

period of minimal aquifer recharge and relatively 

constant water levels in the upper aquifer. For the 

steady-state 1995 model simulation, however, 

ground-water pumpage had been increased to 

26.3 cubic foot per second, due to increased 

demand for public water supply, the heads at 0.9 

feet, and the outflow to the sea at Laguna 

Tortuguero had been lowered considerably. 

Simulated ground-water inflow for 1940 

hydrologic conditions included 35.9 cubic feet per 

second from areal recharge, contributions from 

streamflow along the southern boundary of 1.6 

cubic feet per second, and streamflow infiltration 

to the upper aquifer of 4.2 cubic feet per second. 

Simulated ground-water outflow for 1940 

hydrologic conditions are discharge to springs of 

17.4 cubic feet per second, total ground-water 

withdrawals of 1.0 cubic feet per second, and 

aquifer contribution to streamflow or wetland 

areas of 23.4 cubic feet per second. 

Simulation of Flow in the Upper North Coast Limestone 

Aquifer, Manatí-Vega Baja Area, Puerto Rico

By Gregory S. Cherry
2 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Simulated ground-water inflow for 

hydrologic conditions of March 1995 included 

contributions from streamflow along the southern 

boundary of 1.6 cubic feet per second, areal 

recharge of 35.9 cubic feet per second, and 

streamflow infiltration to the upper aquifer of 

11 cubic feet per second. Simulated ground-water 

outflow for hydrologic conditions of March 1995 

are ground-water withdrawals of 26.3 cubic feet 

per second, discharge from springs of 7.3 cubic 

feet per second, and aquifer contribution to 

streamflow or wetland areas of 14.9 cubic feet per 

second. The overall ground-water budget 

increased from 41.8 cubic feet per second for 

1940 conditions to 48.6 cubic feet per second for 

the hydrologic conditions of March 1995. The 

increase in ground-water budget is a direct result 

of increased ground-water withdrawals, which 

induced greater streamflow infiltration. 

Simulated ground-water flux to Laguna 

Tortuguero for 1940 conditions was 11 cubic feet 

per second, which dropped to 5.2 cubic feet per 

second in March 1995, as the result of extensive 

ground-water pumping. Base flow measurements 

at the outlet of Laguna Tortuguero at station 

number 50038200, from 1995 to the present, 

averaged 6.9 cubic feet per second. Earlier 

measurements, taken from 1974 to 1980, which 

can be considered base flow or flow during 

relatively dry periods, averaged 16.2 cubic feet 

per second.

A transient simulation was conducted for a 

period ending in 1995, using the construction of 

the Laguna Tortuguero outlet in 1943 as a 

reference starting point. The historical pumpage 

was reconstructed from available records for each 

stress period, while recharge rates remained 

relatively constant with slight changes required in 

the river model segment to simulate the water 

level for Laguna Tortuguero. The aquifer heads 

for the 1995 transient simulation were slightly 

higher than the 1995 steady-state simulation, with 

an average absolute deviation of 3.17 feet, 

compared to 3.10 feet.

Sumario

Para entender mejor el sistema 

hidrogeológico del acuífero superior en la 

provincia de la costa norte de Puerto Rico, se 

construyó un modelo digital bidimensional de 

agua subterránea para el área de Manatí-Vega 

Baja. El área que se presenta en este modelo cubre 

unas 79 millas cuadradas dentro de los municipios 

de Manatí y Vega Baja y pequeñas porciones de 

Vega Alta y Barceloneta.

Hay tres ríos principales que fluyen hacia el 

norte y atraviesan el área del modelo de agua 

subterránea: el Río Grande de Manatí, Río Cibuco 

y Río Indio. El acuífero no confinado de la Caliza 

Superior de la Costa Norte se encuentra al norte 

de la latitud 18 grados 25 minutos y se extiende 

hasta áreas de humedales rodeando la Laguna 

Tortuguero, donde el agua subterránea descarga a 

manantiales o directamente a la laguna. En la 

década de 1930, la red de canales y el canal de 

desembocadura a la Laguna Tortuguero fueron 

construidos para drenar las áreas de humedales 

para el control de la malaria y aumentar el área 

cultivable de la caña de azúcar.

Las simulaciones en condición de 

equilibrio del modelo bidimensional de agua 

subterránea se correlacionaron con las 

condiciones que existían antes de la construcción 

del canal de desembocadura de la Laguna 

Tortuguero en 1940, e inclusive fueron calibradas 

según la superficie potenciométrica observada en 

marzo de 1995. En una escala regional, el 

acuífero no confinado de la Caliza Superior de la 

Costa Norte es un sistema difuso de flujo de agua 

subterránea a través de unidades de caliza de 

Aguada y el Aymamón. Los parámetros entrados 

al modelo calibrado de recarga del acuífero 

variaron de 2 pulgadas al año en áreas costeras, 

a 18 pulgadas al año en las áreas elevadas al sur 

de Manatí y Vega Baja. Los valores de 

transmisividad calibrados fluctuaron entre menos 

de 500 pies cuadrados por día en las áreas 

elevadas cercanas a la frontera sureña, y 70,000 

pies cuadrados en las áreas al oeste de Vega Baja. 

El aumento en las extracciones de agua 

subterránea de 1.0 pie cúbico por segundo para las 
Abstract 3

condiciones en 1940, a 26.3 pies cúbicos por 

segundo en 1995, ha reducido la descarga natural 

de agua subterránea a manantiales y áreas de 

humedales, y ha inducido una mayor infiltración 

de los ríos. El drenaje de agua subterránea más 

importante proveniente del acuífero superior es la 

Laguna Tortuguero, con un área de drenaje de 

unas 17 millas cuadradas. La descarga de la 

Laguna Tortuguero hacia el mar por el canal de 

desembocadura ha sido medida cada dos meses 

desde 1974. El efluente representa una 

combinación de descarga de agua subterránea y 

superficial sobre el área de drenaje. 

Las condiciones hidrológicas previas a la 

construcción del canal de desembocadura de la 

Laguna Tortuguero en 1943 pueden considerarse 

como promedio, con un bombeo mínimo de 1.0 

pie cúbico por segundo y niveles hidrostáticos 

más altos, o de 3.3 pies (1.0 metro) sobre el nivel 

medio del mar. El modelo fue calibrado de 

acuerdo con las condiciones de marzo de 1995, 

durante un período de sequía, cuando la recarga al 

acuífero fue mínima. No obstante, para la 

simulación en equilibrio de 1995, el bombeo 

había sido aumentado a 26.3 pies cúbicos por 

segundo, debido a la creciente demanda del 

abasto de agua público y el nivel hidrostático, a 

0.9 pie, y la descarga de agua subterránea al mar y 

a la Laguna Tortuguero había disminuido 

considerablemente.

El flujo simulado que entra al sistema de 

agua subterránea para 1940 consiste en una 

recarga aérea de 35.9 pies cúbicos por segundo, 

contribuciones del caudal a lo largo de la frontera 

sur de 1.6 pies cúbicos por segundo e infiltración 

del caudal al acuífero superior de 4.2 pies cúbicos 

por segundo. El flujo simulado de salida del 

sistema de agua subterránea para 1940 consiste en 

descarga a manantiales de 17.4 pies cúbicos por 

segundo, extracciones de agua subterránea de 1.0 

pie cúbico por segundo y contribución al caudal 

de ríos o áreas de humedales de 23.4 pies cúbicos 

por segundo.

El flujo simulado que entra al sistema de 

agua subterránea para marzo de 1995 consiste 

en contribuciones del caudal a lo largo de la 

frontera sur de 1.6 pies cúbicos por segundo, una 

recarga aérea de 35.9 pies cúbicos por segundo 

e infiltración de caudal al acuífero superior de 

11 pies cúbicos por segundo. El flujo simulado de 

salida del sistema de agua subterránea para marzo 

de 1995 consiste en extracciones de agua 

subterránea de 26.3 pies cúbicos por segundo, 

descarga a manantiales de 7.3 pies cúbicos por 

segundo y contribución al caudal o áreas de 

humedales de 14.9 pies cúbicos por segundo. El 

balance de agua subterránea aumentó de 41.8 pies 

cúbicos por segundo para las condiciones de 1940 

a 48.6 pies cúbicos por segundo para las 

condiciones hidrológicas de marzo de 1995. El 

aumento de agua subterránea es el resultado 

directo de mayores extracciones de agua 

subterránea que indujeron una infiltración mayor 

de caudal.

El flujo de drenaje de agua subterránea 

simulado hacia el drenaje de la Laguna 

Tortuguero para las condiciones de 1940 fue 

de 11 pies cúbicos por segundo, el cual bajó a 

5.2 pies cúbicos por segundo en marzo de 1995 

como resultado de la explotación extensa de agua 

subterránea. Los aforos del caudal de base en la 

desembocadura de la Laguna Tortuguero en la 

estación número 50038200 desde 1995 hasta el 

presente promediaron 6.9 pies cúbicos por 

segundo. Otros aforos realizados desde 1974 

hasta 1980, los cuales pueden considerarse como 

caudal de base o caudal durante períodos de 

relativa sequía, promediaron 16.2 pies cúbicos 

por segundo.

Para el período que finalizó en 1995, se 

realizó una simulación en condición transitoria 

utilizando la construcción de la desembocadura 

de la Laguna Tortuguero en 1943 como punto de 

referencia. El bombeo histórico fue reconstruido 

utilizando documentos disponibles de cada 

periodo, mientras que los índices de recarga 

permanecieron relativamente constantes con 

cambios leves requeridos en la conductancia del 

lecho del río utilizada para regular el flujo hacia la 

Laguna Tortuguero y, de esta forma, calibrar los 

cambios en los niveles hidrostáticos. Los niveles 

hidrostáticos del acuífero para la simulación 

transitoria de 1995 fueron un poco mayores que 

las de la simulación de equilibrio de 1995, con 

una desviación absoluta media de 3.17 pies, 

comparada con 3.10 pies.
4 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

INTRODUCTION

In the Río Grande de Manatí to Río Cibuco area, 

the unconfined upper aquifer provides 80 percent of 

the public water supply to the towns of Manatí and 

Vega Baja (fig. 1). The North Coast Limestone aquifer 

system consists of an upper unconfined aquifer and a 

lower confined aquifer. In 1995, the more productive 

and permeable upper aquifer provided an estimated 

17 million gallons per day (Mgal/d), mostly for public 

water supply, with minor quantities for industrial and 

domestic needs. The lower confined aquifer provides 

substantial quantities of ground water for the watersupply needs of industrial complexes near Barceloneta 

and Manatí (fig. 2). 

The purpose of this study was to enhance 

understanding of the ground-water flow system within 

the Manatí, Puerto Rico 71⁄2-minute quadrangle, by 

developing a two-dimensional ground-water flow 

model to simulate flow in the upper unconfined 

aquifer. This report describes the hydrogeology of the 

Upper North Coast Limestone aquifer, model 

development, and simulation results. The computed 

steady-state model heads were compared to the 

potentiometric surface observed in March 1995, 

during the calibration process. The calibrated flow 

model was then used to (a) assess the historical change 

in the potentiometric surface and aquifer water 

balance resulting from the large-scale dewatering 

works of the early 1940’s, and ground-water 

withdrawals since the early 1960’s; (b) assess the 

regional effects on the upper aquifer from an 

anticipated reduction of ground-water withdrawals for 

public water-supply purposes; and (c) assess the effect 

of changes in land-use patterns, that are expected to 

enhance aquifer recharge.

Description of the Study Area

The Manatí-Vega Baja study area covers 

approximately 79 square miles (mi2

). The area is 

bordered by the Atlantic Ocean on the north and by the 

rugged cone karst topography to the south. The 

western boundary is a north-south line, just west of the 

Río Grande de Manatí, and the eastern boundary is a 

north-south line, just east of the confluence of the Río 

Indio and the Río Cibuco (fig. 1). The area has 

undergone substantial changes in land use (former 

agricultural land developed into urban areas) with 

steady population growth. Like many areas of Puerto 

Rico, much of the arable land in the alluvial valleys 

was planted in sugarcane in the first half of the 1900’s. 

A general decline of sugarcane acreage in the upland 

areas commenced in the 1930’s, when sugarcane 

production areas were converted to fruit crops 

(primarily pineapples). The hydrology of the study 

area has been modified substantially, since the late 

1930’s by reclamation of land for agricultural use and 

malaria control through dewatering of wetlands in 

coastal areas by a system of drainage canals. In 1943, 

construction of an outlet channel connecting Laguna 

Tortuguero to the ocean dewatered additional area by 

lowering the lagoon water-surface elevation. By the 

late 1970’s, sugarcane cultivation had essentially been 

abandoned and land was left fallow or converted to 

pasture for dairy cattle. In the upland plains, the land 

use trend has been from agricultural to urban. Portions 

of the municipios of Vega Baja, Manatí, and 

Barceloneta are within the study area. In these 

municipios, population has increased from 79,271 in 

1950 to 126,662 in 1996 (U.S. Census Bureau, 1998), 

with the highest growth rate occurring within the 

municipio of Vega Baja. Thus, areas formerly utilized 

to grow sugarcane or fruit crops have been rezoned 

for housing (fig. 2). This trend will probably continue 

with the completion of the North Coast 

“Superaqueduct” currently under construction. The 

“Superaqueduct” will increase the availability of 

public water supply from surface-water sources and 

decrease withdrawals from the upper aquifer. An 

increase in housing development is expected to 

enhance aquifer recharge, as storm water runoff 

from developed areas is typically conveyed to the 

sub-surface by construction of injection wells.
Introduction 5

Figure 1. Location of the Manatí-Vega Baja study area and important hydrologic features, North Coast Province, Puerto Rico.
6 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 2. Selected land uses in 1977 and 1987 in the Manatí-Vega Baja study area, North Coast Province, 

Puerto Rico.
Introduction 7

The Manatí quadrangle lies within the North 

Coast Climatic Division (NCCD) of Puerto Rico, as 

classified by the U.S. National Weather Service (U.S. 

Department of Commerce, National Oceanic and 

Atmospheric Administration, 1982). The NCCD is 

characterized by nearly constant trade winds from the 

northeast, that maintain mean monthly temperatures to 

within 3 degrees Celsius (°C) of an annual mean 

temperature of about 25.5 °C. Average annual rainfall 

in the study area ranges from less than 60 inches (in.) 

near the coast to 70 inches in the karst terrain near the 

southern boundary (fig. 3). Long-term records from 

National Weather Service rainfall stations in the study 

area show a relative dry season from December to 

April, and a wet period from May to November, 

associated with the hurricane season. The mean 

monthly rainfall records indicate that May is the 

wettest month, followed closely by November; 

February and March are the driest months. Since 

1899, 72 tropical storms or hurricanes have passed 

within 90 miles of Puerto Rico, with 20 making 

landfall on the island (Gillette and others, 1996). 

These storms produce torrential rains over parts of 

the island; a 10- inch rainfall within a 24-hour period 

has a return frequency of approximately 50 years.

History of Water Use

Ground-water withdrawals in the upper aquifer 

have historically and primarily been for public watersupply purposes. A detailed analysis of Puerto Rico’s 

public water-supply sources in 1959 indicated 

withdrawals from the Puerto Rico Aqueduct and 

Sewer Authority (PRASA) wells located within the 

municipios of Manatí and Vega Baja were about 1.1 

Mgal/d, and that the major springs were important 

contributors to the water-supply system (Arnow and 

Crooks, 1960). Withdrawals from the PRASA wells 

remained essentially unchanged through the year 

1969, when ground-water withdrawals were assessed 

in the Laguna Tortuguero ground-water basin and 

estimated to be 1.95 Mgal/d (3.0 cubic feet per second 

(ft3

/s), Bennett and Giusti, 1972). More detailed data 

on the development of the aquifer as a public watersupply source were compiled from the PRASA yearly 

operations summary reports, which are available by 

region from 1982 to 1995. In addition, the Water 

Franchise Division of the Puerto Rico Department of 

Natural and Environmental Resources (PRDNER) 

maintains detailed records of the withdrawal rates for 

industrial wells in the area since 1974.

Historical ground-water use for the study area is 

summarized in figure 4. In the Manatí 71⁄2-minute 

quadrangle area, ground-water withdrawals from the 

upper aquifer in March 1995 were estimated as 

follows: 14.7 Mgal/d for public water-supply 

purposes, 1.7 Mgal/d for industrial self-supplied use, 

and 0.5 Mgal/d for agricultural use, for a total of 16.9 

Mgal/d (26.1 ft3/s) (Conde-Costas and Rodríguez, 

1997). Ground-water withdrawals however, may have 

reached a maximum 19.4 Mgal/d (30.0 ft3

/s) in 1984, 

when several irrigation wells with a withdrawal rate of 

about 3.0 Mgal/d were used for rice cultivation 

(Gómez-Gómez and Torres-Sierra, 1988) in the Río 

Cibuco valley (wells 32, 33, 35, and 38; fig. 4). By 

about 1985, the irrigation wells had ceased operation, 

and between 1985 and 1989 several public watersupply wells in Barrios Coto Norte and Coto Sur of 

Manatí were closed because of contamination by 

organic solvents including methylene chloride (at Coto 

Norte) and nitrates (at Coto Sur) (Conde-Costas and 

Gómez-Gómez, 1999). 

 The only public water-supply source from 

surface water is a filtration plant located along Río 

Indio in Barrio La Trocha of Vega Baja. This public 

water-supply filtration plant produced an average of 

1.3 Mgal/d in 1995, up from 1.0 Mgal/d in previous 

years (Molina-Rivera, 1998). Also contributing 

approximately 0.6 Mgal/d in 1995 for public water 

supply to the municipio of Vega Baja is a surfacewater filtration plant located south of the study area 

with its source being the Río Unibón, a tributary of the 

Río Indio (refer to fig. 1 for locations). Completion of 

the “Superaqueduct” will increase surface-water 

deliveries and allow selected public-supply wells to be 

placed on stand-by status (fig. 4).
8 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 3. Average annual rainfall distribution (modified from Colón, 1983) and location of stream-gaging and precipitation stations in the ManatíVega Baja study area, North Coast Province, Puerto Rico.
Hydrogeologic Setting 9

Acknowledgments

A special thanks to the landowners who 

provided access along several segments of Quebrada 

Hicatea. The information provided by these 

individuals proved useful in gaining an understanding 

of the system. Fernando Gómez-Gómez and Sigfredo 

Torres-González, of the U.S. Geological Survey 

(USGS) Caribbean District, provided helpful feedback 

for understanding the ground-water system and 

management of the many MODFLOW files. Ronald 

Richards of the Caribbean District, assisted the author 

with seepage runs along various reaches of the Río 

Grande de Manatí and Río Indio. Francisco 

Maldonado of the Caribbean District, provided 

assistance with the figures.

HYDROGEOLOGIC SETTING

Within the study area, the North Coast 

Limestone aquifer system consists of two aquifers 

(fig. 5). An upper unconfined aquifer is separated from 

a lower confined aquifer by a confining unit. The 

highly permeable upper aquifer provides the majority 

of water used for public supply and the lower aquifer 

is an important source of water for industrial 

complexes located near the towns of Barceloneta and 

Manatí. The confining unit is discontinuous west of 

the study area, grading into more permeable limestone 

units that are part of the lower aquifer. To the east, the 

confining unit grades into more permeable limestone 

units that are considered to be part of the unconfined 

upper aquifer. The locations of wells used to define the 

upper and lower aquifers and confining unit are shown 

in figure 6. These sites are described in table 1.

Geologic Setting

Tertiary limestones within the North Coast 

Province generally strike to the west and dip gently to 

the north from 6 to 7 degrees near the contact with the 

volcanic rocks south of the study area, and from about 

1 to 2 degrees near the coast (Monroe, 1980). These 

rocks, grouped into six formations, include in 

ascending order: the middle Oligocene San Sebastián 

Formation, the late Oligocene Lares Limestone, the 

Oligocene and Miocene Cibao Formation, the 

Miocene Aguada and Aymamón Limestones, and the 

lower Miocene Camuy Formation (fig. 5). Alluvial 

deposits occur in the river valleys of the Río Grande 

de Manatí and the Río Cibuco, with a sequence of 

“blanket sands” overlying limestones in upland areas 

(fig. 7).

Figure 4. Historical and projected future use of ground water in the Manatí-Vega Baja study area, 

North Coast Province, Puerto Rico.
10 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Rocks comprising the basal part of the Tertiary 

rock sequence in the North Coast Province, namely the 

San Sabastián Formation, the Lares Limestone, 

Mucarabones Sand, and Cibao Formation were 

defined by Zapp and others (1948) as the Río 

Guatamala Group. The San Sabastián Formation 

represents an initial interval of clastic deposition 

followed by a period when terrestrial material was 

absent and the relatively pure Lares Limestone was 

deposited. The Lares Limestone grades laterally into 

the Mucarabones Sand, just east of Corozal (Monroe, 

1980). The Cibao Formation, divided into six 

members, represents a period dominated by clastic 

deposition is described as a calcareous clay, earthy 

limestone, or marl. Monroe (1971) mapped an outcrop 

of the Montebello Limestone member on the eastern 

side of the Río Grande de Manatí (fig. 7), but west of 

the Río Grande de Manatí, he subdivided the Cibao 

Formation into a lower member named the Montebello 

Limestone and an informally named upper member. 

Just east of the Río Grande de Manatí, the Cibao 

Formation grades laterally to the east and is divided 

into the Río Indio Limestone member and the 

Quebrada Arenas Limestone member. Further to the 

east of Río de la Plata, the lower two-thirds of the 

Cibao Formation grades laterally into the 

Mucarabones Sand (Monroe, 1980). The other two 

members, the Almirante Sur Sand and the Miranda 

Sand, are discontinuous, with most outcrops located 

between the Río Indio and Río Cibuco. 

Figure 5. Stratigraphic nomenclature of the middle Tertiary sequence and hydrogeologic units of 

the North Coast Limestone aquifer system, Puerto Rico. Stratigraphic nomenclature modified 

from Monroe (1980). Geologic nomenclature of Monroe (1980), adopted by Rodríguez-Martínez 

(1995) in his description of the hydrogeologic framework of the North Coast Province of Puerto 

Rico, is used for the present report. 
Hydrogeologic Setting 11

Figure 6. Location of wells, springs, and filtration plant in the Manatí-Vega Baja study area, North Coast Province, Puerto Rico.
12 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Table 1. Characteristics of well data-collection sites and location within the Manatí-Vega Baja ground-water 

model, North Coast Province, Puerto Rico 

[X, indicates data are available] Map number

 Well

 name

USGS site

identification

number

 RowColumn Pre-developmentwater altitudePost-development water altitudeLithologic data Ground-waterdischargeTransmissivity determined at well

1 Plazuela 2 1827570663256 13 2 X 

2 January Textile 1 1827250663232 16 4 X X X

3 Mamey Spring 1827590663041 12 15 X

4 Tierras Nuevas 1828040663016 12 17 X

5 Boquillas 1827520662937 13 21 X X

6 Cubano Jacobo 1827420662927 14 22 X X X

7 Meléndez 1827550662856 13 25 X

8 Cruz Rosa Rivas 1827050662952 18 20 X X

9 Rabanos 1827140662925 17 22 X X X

10 Cubano Jacinto 1827010662902 18 25 X X

 11 Dupont 3 (upper) 1826570662848 16 28 X

12 Álvarez 1827320662828 15 28 X

13 IAS-1 1827310662811 15 29 X

14 Dupont 3 (lower) 1827340662809 15 30 X

15 Laguna South Spring 1827370662707 15 35 X

16 Martínez 1828350662558 9 42 X

17 Cerro Guarico 1828040662457 12 48 X X

18 NC-14 1827430662522 14 46 X X

19 Tortuguero TW3 1827120662517 17 46 X

20 Tortuguero 2 1827150662458 17 48 X X X

20a Tortuguero 1 1827140662502 17 48 X X X

21 Owens-Illinois 1826430662602 20 42 X

22 Agregado 1826360662507 21 47 X

23 Algarrobo 1826390662434 21 50 X X

24 Vega Baja 2 1826520662415 19 52 X X

25 Vega Baja 3 1826440662404 20 53 X X X

26 Vega Baja 4 1826460662359 20 54 X X

27 Ojo de Agua Spring 1826570662506 18 53 X

28 NC-9 1827350662343 15 55 X X

29 China Caribe 1827170662326 17 57 X X X
Hydrogeologic Setting 13

30 Kirk Wing 1827040662311 18 58 X

31 Vega Baja 1 1826480662309 20 58 X X

32 Rice Program 5 1827390662230 14 62 X X

33 Rice Program 4 1827510662219 13 63 X X

34 Central San Vicente 1827430662158 14 65 X X

35 Ceiba 1 1826560662216 19 64 X X X

36 Ceiba 2 Carmelita 1826400662158 20 65 X X

37 Monserrate 1826300662150 21 66 X X X

38 Rice Program 3 1827060662135 18 68 X X

39 Sabana Hoyos 3 1826540662110 19 70 X X

40 Warner Lambert 2 1827070662106 18 70 X

41 Warner Lambert 1 1827100662107 17 70 X X

42 Sabana Hoyos 2 1827120662037 17 73 X X X

43 Jardín Dorado 1 1827390662058 14 71 X X

44 Pennock Gard. 2 1827500662049 13 72 X

45 Cerro Gordo Nursery 1 1827560662052 13 72 X

46 Pennock Gard. 3 1827550662042 13 73 X

47 Finca Cibuco 1828540662119 7 69 X X

48 Santa Rosa 2 1826100662047 23 72 X

49 BVAW18 1825200662047 29 72 X X X

50 Arraiza 1824570662151 31 66 X X

51 Almirante 2 1824520662207 31 64 X X X

52 Almirante 3 1825590662221 25 63 X X X

53 La Trocha 1826100662254 23 60 X X

54 Pantojas 1825290662325 27 57 X X

55 Villa Pinares 1825320662336 27 56 X X X X

56 Rosario 2 1826150662353 23 54 X X

57 Alturas 1826160662410 23 52 X X

58 Pugnado Afuera 1 1825530662428 25 51 X X

59 Pugnado Afuera 2 1825440662438 26 50 X X X

60 Palo Alto 3 1825480662510 26 47 X X

61 Finca EM 1824280662512 34 47 X X Map number

 Well

 name

USGS site

identification

number

 RowColumn Pre-developmentwater altitudePost-development water altitudeLithologic data Ground-waterdischargeTransmissivity determined at well

Table 1. Characteristics of well data-collection sites and location within the Manatí-Vega Baja ground-water 

model, North Coast Province, Puerto Rico–Continued 
14 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

62 E. Martínez 1824250662529 34 45 X

63 Perica 1824260662604 34 42 X

64 Palo Alto 1 1825310662626 27 40 X X

65 Pugnado 3 1825550662618 25 40 X X X

66 Palo Alto 2 1826140662615 23 41 X X

67 Sobrino 1826190662557 22 42 X X

68 Coto Norte 3 1826340662625 21 40 X X

69 NC-4 1826330662626 21 40 X X

70 Coto Norte 2 1826300662635 21 39 X

71 Coto Sur 2 1825520662647 25 38 X X X

72 Coto Sur 7 1825480662657 26 37 X X

73 Coto Sur 5 1825460662712 26 35 X X

74 Ortho Lab 1826140662709 23 35 X X

75 Coto Sur (WH) 1825460662730 26 33 X X X

76 Coto Sur 6 1825420662737 26 33 X X

77 Hnos Hill 2 1825510662725 25 34 X X

78 Coto Sur 1 1825400662754 26 31 X X X

79 Roche 1825380662759 26 30 X X

80 Coto Sur 3 1825540662749 25 31 X X X

81 Campo Alegre 1826080662759 24 31 X X X

82 Ciordia 2 1826190662742 23 32 X

83 Eaton Labs 1826150662735 23 33 X X X

84 Coto Norte 1 1826230662732 22 33 X X X

85 Atenas 1826300662740 21 32 X

86 Schering Plough 2 1826250662805 22 30 X X

87 Schering Plough 1 1826290662808 22 30 X X

88 Davis & Geck S 1826270662826 22 28 X X

88a Davis & Geck N 1826270662824 22 28 X

89 IAS-2 1826250662805 22 29 X X

90 Cordova Dávila 1826170662901 23 25 X X X

91 Vocacional 1826050662833 24 27 X X

92 Acrópolis 1825340662830 27 28 X Map number

 Well

 name

USGS site

identification

number

 RowColumn Pre-developmentwater altitudePost-development water altitudeLithologic data Ground-waterdischargeTransmissivity determined at well

Table 1. Characteristics of well data-collection sites and location within the Manatí-Vega Baja ground-water 

model, North Coast Province, Puerto Rico–Continued 
Hydrogeologic Setting 15

93 USGS Hill 1 1825140662821 29 29 X X

94 USGS Hill 2 1825060662802 30 30 X X

95 Finca Gil 1825150662841 29 27 X X

96 Escal Fullery 1825300662854 28 25 X X X

97 Coto Sur 4 1825140662902 29 24 X X X

98 Monserrate Sur 1824120662949 35 20 X X

99 Oficina PRASA 1826050662925 24 22 X X X

100 Manatí 1 1825490663002 26 19 X X X X

101 Manatí 2 1825590663005 26 18 X X X X

102 Mckesson 1825590663025 25 16 X X

103 Calaf Frederico 1826210663025 23 17 X X X

104 Manatí 3 1825490663043 25 15 X X

105 Cantito La Luisa 1827100663037 16 15 X

106 Ojo de Guillo Spring 1825410663136 26 9 X

107 Canning 1 1826170663200 23 5 X

108 Fortuna 1826470663308 20 1 X

109 Jimenez Amador 1829030662405 6 53 X X

110 Jimenez Dairy 1829240662343 4 55 X

111 Albalabejo MW1 1824430662250 32 60 X

112 Albalabejo MW2 1824380662246 33 61 X

113 Albalabejo MW3 1824350662245 33 61 X

114 Albalabejo MW4 1824430662240 32 61 X

115 Albalabejo MW5 1824310662246 33 61 X

116 Vega Baja Soid 

Waste MW1

1826140662318 23 58 X

117 Vega Baja Solid

Waste MW2

1826170662324 23 57 X

118 Vega Baja Solid

Waste MW3

1825560662323 25 57 X

119 Bajura Adentro 1 1825200663043 29 15 X X

120 Bajura Adentro 3 1825180663037 29 16 X Map number

 Well

 name

USGS site

identification

number

 RowColumn Pre-developmentwater altitudePost-development water altitudeLithologic data Ground-waterdischargeTransmissivity determined at well

Table 1. Well data-collection sites and location within the Manatí-Vega Baja ground-water model, North Coast 

Province, Puerto Rico–Continued 
16 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 7. Generalized surficial geology of the Manatí-Vega Baja study area and location of hydrogeologic cross sections, North Coast Province, 

Puerto Rico. Cross sections are shown in figure 8 (modified from Monroe, 1980).
Hydrogeologic Setting 17 Figure 8. Generalized hydrogeologic cross sections of the Manatí-Vega Baja study area, North Coast Province, Puerto Rico. Refer to figure 7 for cross-section location.
18 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

The Aguada Limestone is considered to be 

transitional between the Cibao Formation and the 

Aymamón Limestone. The Aguada is a calcarenite and 

less fossiliferous than the underlying Cibao Formation 

(Monroe, 1980). The Aguada Limestone contains 

quartz grains, indicating that the rivers that formed the 

Cibao Formation were still active (Monroe, 1980), 

whereas the Aymamón Limestone is a pure massive 

limestone with some dolomite replacement near the 

coast. Where the Aymamón Limestone has not 

reprecipitated to form a resistant caprock or mogotal 

features, the unit may be a fragmented or rubbly chalk 

susceptible to dissolution. The dissolution of the 

surrounding limestones and drainage into cracks and 

conduits over time has produced deposits of quartz 

sand, clayey sand, sandy clay, and clay, called the 

blanket sand deposit (Briggs, 1966). 

The valleys formed by the Río Grande de 

Manatí and the Río Cibuco are filled with alluvial 

deposits of mostly fine sand, silt, and clay. The area 

south of Laguna Tortuguero is characterized by sand 

deposits, having a composition of nearly 99 percent 

silica (Meyerhoff and Frazier, 1945). Near the coast, 

and locally to as much as 1,000 feet (ft) offshore, there 

are remnants of cemented Pleistocene eolian dunes 

(eolianite deposits).

The maximum thickness for limestone units in 

the study area is 220 ft for the San Sebastián 

Formation, 850 ft for the Lares Limestone, 1,010 ft 

for the Cibao Formation, 325 ft for the Aguada 

Limestone, and 635 ft for the Aymamón Limestone 

(Monroe, 1980; Rodríguez-Martínez, 1991; 

Rodríguez-Martínez and others, 1992). The thickness 

of the alluvial deposits varies greatly along the Río 

Grande de Manatí and the Río Cibuco. In general, the 

thickness of the alluvial deposits along the Río Grande 

de Manatí is 100 ft where deposits overlie the Lares 

Limestone in the area north of Ciales (S. TorresGonzález, USGS, written commun., 1999), and to 300 

ft downstream where the floodplain widens near 

Highway PR-2 (Gómez-Gómez, 1984). The thickness 

of the alluvial deposits along the Río Cibuco varies 

from approximately 120 ft (Torres-González and Díaz, 

1985) in the coastal floodplain near Highway PR-2 to 

280 ft downstream along the incised channels of the 

Río Cibuco near Vega Alta (Gómez-Gómez and 

Torres-Sierra, 1988). According to drillers’ logs of 

wells in the area, the maximum documented 

thickness of the surficial “blanket sand” deposits is 

approximately 110 ft in Barrio Coto Sur of Manatí, 

but generally is not more than 50 ft (Gómez-Gómez 

and Torres-Sierra, 1988).

Upper North Coast Limestone Aquifer

The upper aquifer is defined as the saturated, 

freshwater portions of the Aymamón Limestone, the 

Aguada Limestone, and the alluvial deposits of the Río 

Grande de Manatí and the Río Cibuco (fig. 8). The 

southern boundary of the upper aquifer is south of the 

Aguada/Aymamón contact near latitude 18°25’ 

(F. Gómez -Gómez, USGS, written commun., 1999), 

and can be delimited as the southernmost point where 

the Aguada Limestone is saturated and is considered 

to be an aquifer. Although the limestone units have a 

combined thickness of as much as 1,000 ft, the 

maximum saturated thickness of the freshwater aquifer 

is approximately 450 ft near Highway PR-2 (fig. 9). 

The relatively impermeable upper member of the 

Cibao Formation underlies the unconfined upper 

aquifer and dips northward at about 3 degrees, causing 

the freshwater lens to thicken northward towards 

Highway PR-2, where it is underlain by saltwater. The 

saltwater wedge thickens and becomes shallower 

towards the coast, which causes the freshwater lens to 

thin in that direction (Rodríguez-Martínez and others, 

1992) (fig. 8). 

Hydraulic Properties

The regional distribution of transmissivities for 

the upper aquifer can be estimated by two methods: 

(a) using specific-capacity data available in drillers’ 

well construction logs and applying the Theis and 

others (1963) method to calculate transmissivity; and 

(b) using the average hydraulic conductivity estimates 

for each of the major hydrogeologic units that 

constitute the upper aquifer in conjunction with areal 

estimates of the freshwater thickness.
Hydrogeologic Setting 19

Figure 9. Estimated altitude of the base of the upper aquifer in the Manatí-Vega Baja study area, North Coast Province, Puerto Rico.
20 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

To compute transmissivity from specificcapacity data using the Theis and others (1963) 

method, the following information is needed: aquifer 

type (confined or unconfined), static water level, 

pumping water level, well discharge rate, duration of 

specific-capacity test, effective radius, and the 

estimated specific yield or storage coefficient. An 

effective radius of 1 ft was used where no cavernous 

conditions exist, whereas an effective well radius of 

5.0 ft was used for wells penetrating cavernous zones. 

Conduits in the limestone and the percentage of 

aquifer thickness penetrated by individual wells can 

affect computed results of individual pumping tests, so 

specific capacity data can not be related directly to 

transmissivity. Calculated transmissivity values for 

wells that penetrate areas of voids and for wells open 

to a greater saturated thickness of the same 

hydrogeologic unit can be erroneously high. Thus, in 

developing the areal distribution of transmissivity by 

this method, subjective reasoning must be used in 

adjusting (or not) the transmissivity value obtained for 

each well. The transmissivity estimated by the specific 

capacity or any given methodology, however, applies 

only to the screened interval of the well, and an 

adjustment of the calculated transmissivity may not be 

applicable locally. This is the case where wells 

indicate that secondary porosity development is highly 

stratified, as evidenced in the upper aquifer of the 

Vega Alta area. 

The distribution of transmissivity calculated by 

using the available specific-capacity data indicates 

there are two areas of high transmissivity near Manatí, 

and another southwest of Vega Baja. In these areas, the 

transmissivity values decrease both to the north and 

south within the limestone units, and in the part of the 

aquifer contained within the alluvial deposits (fig. 10). 

Although transmissivity values are relatively high, 

they are about one half that obtained from the upper 

aquifer in the adjacent Barceloneta and Vega Alta 

quadrangles. Southwest of the town of Barceloneta, in 

the Aymamón Limestone, and north of the town of 

Vega Alta, in the Aymamón and Aguada Limestones, 

transmissivity has been estimated to be as high as 

150,000 feet squared per day (ft2

/d) (Gómez-Gómez 

and Torres-Sierra, 1988; Torres-González, 1985; 

Torres-González and others, 1996). In coastal areas, 

fine-grained alluvium and marsh deposits may fill the 

vuggy and locally fissured saturated parts of the 

Aymamón Limestone, reducing the hydraulic 

conductivity, as seems to be the case in the coastal 

plain of the Vega Alta quadrangle area (F. GómezGómez, USGS, written commun., 1999).

The distribution of transmissivity also was 

calculated using average values of hydraulic 

conductivity for the two limestone units and the 

freshwater saturated thickness of the aquifer (fig. 11) 

determined that the hydraulic conductivity is 160 feet 

per day (ft/d) for the Aymamón Limestone and 70 ft/d 

for the Aguada Limestone, and 15 and 10 ft/d, 

respectively for the alluvial deposits within the Río 

Grande de Manatí and Río Cibuco valleys. The 

saturated thickness of the upper aquifer was 

determined from seven deep and two shallow test 

holes drilled as part of previous ground-water 

resources assessments (Rodríguez-Martínez, 1995) 

(figs. 8 and 9). 

The saturated thickness of the alluvium is an 

estimate based on studies conducted by the USGS, 

using electric surface resistivity techniques to 

delineate the depth to the alluvial/limestone contact in 

the Río Cibuco and the Río Grande de Manatí valleys 

(Gómez-Gómez, 1984; Torres-González and Díaz, 

1984; and S. Torres-González, USGS, written 

commun., 1998). Transient electromagnetic surveys 

were conducted along the southern shore of Laguna 

Tortuguero and areas north to northeast of the lagoon, 

to estimate the thickness of the freshwater lens in these 

areas. Values of transmissivity for alluvial deposits in 

the Río Grande de Manatí and Río Cibuco valleys are 

based on estimated averages of the hydraulic 

conductivity of alluvium, which ranges from 25 to 40 

ft/d for the lower Río Grande de Arecibo valley 

(Quiñones-Aponte, 1986), and from 20 to 30 ft/d for 

the lower Río Grande de Manatí valley (GómezGómez, 1984). Near the coast, the lower 

transmissivity values are due to the decrease in 

thickness of the freshwater lens.
Hydrogeologic Setting 21Figure 10. Transmissivity distribution for the upper aquifer as estimated from well specific-capacity data, Manatí-Vega Baja study area, 

North Coast Province, Puerto Rico.
22 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 11. Transmissivity distribution for the upper aquifer as estimated using average hydraulic conductivity values for freshwater-saturated hydrogeologic units in the Manatí-Vega Baja study area, North Coast Province, Puerto Rico.
Hydrogeologic Setting 23

Direction of Ground-Water Flow

Ground water in the upper aquifer travels 

downdip within the Aguada Limestone to the more 

transmissive Aymamón Limestone. Wells drilled south 

of the southern aquifer boundary, however, may 

penetrate a saturated zone within the Aguada 

Limestone updip of the aquifer. In this area, ground 

water essentially flows downdip along the bedding 

plane of the relatively impermeable Cibao Formation 

until it reaches the upper aquifer (Bennett and Giusti, 

1972).

General movement of ground water in the upper 

aquifer is from the highlands in the karst terrain 

northward towards Laguna Tortuguero, the coastal 

plain, and shoreline, as evidenced in the 

potentiometric surface as mapped in March 1995 

(fig. 12). South of Highway PR-670, the water-table 

gradient reaches 250 ft per mile (ft/mi). This gradient 

is essentially equivalent to the dip of the top of the 

confining unit, which regionally averages 3 degrees 

(equivalent to about 160 ft/mi). The water-table 

gradient within the upper aquifer from Highway 

PR-670 at Barrio Coto Sur to the coast, where the 

upper aquifer exists primarily as a lens of freshwater 

overlying saltwater, was estimated to range between 

3 and 6 ft/mi in 1970 (Bennett and Giusti, 1972) and 

was found to be 3 ft/mi in 1995 (Conde-Costas and 

Rodríguez, 1997). The relatively flat potentiometric 

surface that currently exists is caused in part by 

ground-water withdrawals, which in the study area 

have increased from about 5 Mgal/d in 1969 to more 

than 19 Mgal/d in 1984, and to 17 Mgal/d in 1995 

(Bennett and Giusti, 1972; Conde-Costas and 

Rodríguez, 1997; Molina-Rivera, 1998) (fig. 4). As a 

result, ground water, which previously would have 

discharged to Laguna Tortuguero and to the springs 

south of the lagoon, is presently captured by wells.

Hydraulic Connection with Surface-Water Features

A general summary of the surface-water 

hydrology for the study area can be obtained from a 

regional assessment conducted by Giusti and Bennett 

(1976). This information is useful to determine the 

interaction of streams and coastal lagoons with the 

upper aquifer. An overall knowledge of contributing 

areas to streamflow and flow duration provides 

valuable insight for accessing river gains and losses to 

the upper aquifer along various river segments. The 

hydrologic budgets obtained from that study were the 

basis for initial recharge estimates used in this study. 

According to Giusti and Bennett (1976), 

between November 1969 and October 1970 (a period 

with 20 percent above average rainfall), streams 

draining volcanic rock areas south of the limestone 

region had a base flow of 1 to 2 ft3

/s per square mile 

(representing 15 to 25 in. of annual rainfall). In 

streams draining the limestone terrain of the north 

coast, Giusti and Bennett (1976) estimated a base flow 

of only 0.5 to 1 ft3

/s per square mile (representing 7 to 

15 in. of annual rainfall). In addition, Giusti and 

Bennett (1976) also obtained a ratio of base flow to 

total flow near 0.40 for the limestone region. This ratio 

of base flow to total flow was used to estimate the 

surface-water contribution near the southern boundary 

of the upper aquifer. 

Within the study area, the Río Grande de Manatí 

and Río Cibuco are the only major streams having 

headwaters in the volcanic terrain and traversing the 

limestone area. These streams have a combined 

drainage basin area of 168 mi2

 within the volcanics, 

and approximately 128 mi2 within the limestone 

outcrop areas. With the exception of 6 mi2 of drainage 

area near the insular hydrologic divide that is 

regulated by the Lago Guineo and Lago Matrullas 

dams, the flow in these streams is unregulated. Gaging 

stations in the study area at the Río Grande de Manatí 

near Manatí has been operational from 1970 to the 

present (50038100), and at the Río Cibuco at Vega 

Baja near Highway PR-2 (50039500) from 1973 to the 

present (fig. 3). Prior to the installation of the gaging 

station for Río Cibuco at Highway PR-2 (50039500), 

the USGS maintained a gaging station at Central San 

Vicente (50039600) from 1969 to 1972. In addition to 

these gaged sites, the USGS has obtained bi-monthly 

instantaneous discharge measurements at a waterquality station (50038200) at the outlet channel of the 

Laguna Tortuguero (fig. 3) since March 1974. 
24 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 12. Potentiometric surface of the upper aquifer during March 1995, Manatí quadrangle, 

North Coast Province, Puerto Rico (modified from Conde-Costas and Rodríguez, 1997).
Hydrogeologic Setting 25

Discharge from Laguna Tortuguero through the 

outlet channel to the sea is a combination of groundwater discharge from the upper aquifer and surfacewater runoff in the vicinity of the lagoon. The base 

flow of the Río Grande de Manatí at the gaging station 

(50038100) averages 105 ft3/s, with the flow equal to 

or exceeding 84 ft3

/s about 90 percent of the time 

(from 1970 to 1997), and a minimum recorded 

instantaneous discharge of 28 ft3

/s (January 23, 1995). 

Base flow at the Río Cibuco gaging station averages 

31 ft3/s, with the flow equal to or exceeding 22 ft3/s 

about 90 percent of the time (from 1973 to 1997), and 

a minimum recorded instantaneous discharge of 7.2 

ft3

/s (May 2, 1995). The Río Indio and its tributaries 

contribute approximately 30 percent of the base flow 

of the gaging station. 

Low-flow discharge at the gaged sites have been 

decreasing, which could be related to streamflow 

capture upstream primarily for public water-supply 

purposes, in addition to a general decline of the 

potentiometric surface in the upper aquifer. Public 

water-supply withdrawal rates upstream of the gaged 

stations for 1995 were estimated as follows: 9.9 ft3

/s 

captured from the Río Grande de Manatí (upstream of 

the volcanic/limestone contact), 5 ft3/s captured from 

the Río Cibuco (upstream from the volcanic/limestone 

contact), and 3.9 ft3

/s captured from the Río Indio 

(Molina-Rivera, 1998). 

Although a substantial portion of the low flows 

are captured, these streams also receive discharge 

from public wastewater treatment plants. The Río 

Grande de Manatí receives 1.5 ft3/s (all from locations 

from the town of Ciales and upstream); the Río Cibuco 

receives 2.7 ft3

/s, of which, 1.5 ft3/s is discharged to 

the stream within the lower valley from the town of 

Vega Alta and the remainder upstream of the volcanic/

limestone contact; and, 0.8 ft3/s is discharged to 

tributaries of the Río Indio (Molina-Rivera, 1998).

The most prominent ground-water discharge 

feature for the upper aquifer is Laguna Tortuguero. 

The mean annual ground-water discharge into Laguna 

Tortuguero was estimated as 21 ft3

/s by Bennett and 

Giusti (1972), which was comparable to the 22 ft3/s 

mean annual discharge rate through the ocean outlet 

channel obtained by Quiñones and Fusté (1978). The 

average of 30 bi-monthly instantaneous discharge 

measurements at the outlet canal 50038200, obtained 

between February 1990 and December 1994, was only 

11 ft3

/s (Curtis and others, 1991, 1992; Díaz and 

others, 1993, 1994, 1995). The apparent reduction in 

discharge from Laguna Tortuguero to the ocean is 

probably caused by increases in ground-water 

withdrawals. The combined effect of dredging the 

Laguna Tortuguero ocean outlet and ground-water 

withdrawals has contributed to a general lowering of 

the water level in the lagoon, which may have been as 

high as 5 ft above mean sea level prior to 1943, 3.3 ft 

in the late 1960’s (Bennett and Giusti, 1972), 1.5 ft in 

1975 (Quiñones-Márquez and Fusté, 1978), and 0.9 ft 

in 1995 (Conde-Costas and Rodríguez, 1997).

The ground-water/surface-water interaction 

between the upper aquifer and Río Grande de Manatí, 

Río Indio, and Río Cibuco was assessed by reviewing 

available data on stream low-flow discharge rates and 

duration curves. Several low-flow measurements were 

made in the lower Río Grande de Manatí as part of this 

study; low-flow was at near-record levels during the 

drought period of 1994. The discharge measurements 

were made for a 1.7 mi reach approximately 5.2 mi 

upstream and at a point on the river located 3.5 mi 

upstream of USGS gaging station 50038100 (river 

reach 1 in fig. 3). North of the reach are two PRASA 

public-supply wells on Highway PR-2, Manatí 1 and 

Manatí 2, which have a combined withdrawal rate of 

3 ft3

/s. The discharge measurements were made on 

July 9, 1997, when streamflow had a discharge of 

81 ft3/s. This flow rate is equaled or exceeded more 

than 90 percent of the time, according to the 

streamflow record for the period from 1970 to 1997 

at gaging station 50038100. The difference in 

discharge between both sites indicated a loss of 5 ft3

/s 

to the aquifer, of which 3 ft3/s could be accounted for 

by ground-water withdrawals from the two public 

water-supply wells and an industrial well (Safety 

Kleen) just north of the two supply wells. Low-flow 

measurements cannot be used to determine the 

interaction of the aquifer approximately 3 mi 

downstream of the gage, since the elevation of the 

streambed is below sea level (Gómez-Gómez, 1984) 

and streamflow is affected by tides during low-flow 

periods.
26 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Ground-water discharge to the Río Indio is 

indicated by a series of springs along its course and 

low-flow measurements made on April 3, 1997, and 

May 6, 1997 (river reach 2 in fig. 3). Net river gains 

ranging between 1 and 2 ft3/s were determined by lowflow measurements at low-flow partial-record station 

50038895 between Highway PR-646 and Barrio Río 

Abajo, near Highway PR-22 (Santiago-Rivera, 1998). 

Low-flow measurements made on February 20, 1959, 

indicated a net gain for the Río Indio of 3.1 ft3

/s for a 

reach from latitude 18°23’39” longitude 66°23’42” to 

latitude 18°26’19” longitude 66°22’13”.

Assessment of the surface-water/ground-water 

interaction between the Río Cibuco and the upper 

aquifer was obtained as part of a previous study 

conducted by the USGS to develop a ground-water 

flow model for the Vega Alta area (Gómez-Gómez and 

Torres-Sierra, 1988). The Vega Alta area ground-water 

flow model indicates that the Río Cibuco may be 

contributing 6 ft3/s to the upper aquifer. Low-flow 

measurements made on April 12, 1994, estimated a 

5.5 ft3/s loss to the aquifer.

Recharge

Although some reaches of rivers and streams are 

important sources of ground-water recharge, most 

aquifer recharge in this region is from infiltration of 

rainfall through the limestone outcrops via runoff to 

sinkholes and enclosed topographic depressions. 

Within these areas, recharge, which has been estimated 

by ground-water flow models, is in the range of 10 to 

20 inches per year (in/yr) (Heisel and others, 1983; 

Gómez-Gómez and Torres-Sierra, 1988; and TorresGonzález and others, 1996).

An estimate of the amount of rainfall and 

subsequent infiltration into the upper aquifer near the 

Aguada/Aymamón contact (latitude 18°25’) was made 

as part of this study by taking regular discharge 

measurements at Quebrada Hicatea (fig. 13). This 

stream course originates within the outcrop area of the 

confining unit and ends in a swallow hole near the 

southern boundary of the study area. The average base 

flow from periodic flow measurements conducted at 

Quebrada Hicatea for a 1-year period (June 1997 to 

May 1998) was 0.2 ft3/s. By applying the average ratio 

of base flow to total flow of 0.4 calculated for streams 

in the North Coast Limestone area (Giusti, 1978), the 

average discharge for Quebrada Hicatea (June 1997 to 

May 1998) was estimated to be 0.5 ft3/s. This 

estimated discharge for the 1-year period is equivalent 

to 6 inches per year (in/yr) of rainfall over the drainage 

area of Quebrada Hicatea. The 6 in/yr probably 

represents a low recharge estimate, which could 

average (on a long-term basis) as much as 15 in/yr in 

this particular area. This range in recharge results from 

uncertainties associated with defining drainage areas 

within the limestone terranes, and also because 

precipitation that occurred during the year in which 

the discharge measurements were made was only 43.8 

in., which was 40 percent below the long-term normal 

of 70.2 in. for the Morovis station (National Climate 

Data Center, webmaster@ncdc.noaa.gov, 1998).

Major exceptions to the estimated maximum 

areal rainfall recharge rate of 20 in/yr can be expected 

in areas where there is urban development within 

topographically enclosed depressions. In the ManatíVega Baja area, rainfall runoff is conveyed to the 

upper aquifer by injection wells or storm sewers 

that discharge to existing sinkholes or caverns. This 

land-use modification results in a decrease of 

evapotranspiration, as determined in a study within a 

5,000-acre watershed in the upland volcanics of Puerto 

Rico (Ramos-Ginés, 1997). The results obtained by 

Ramos-Ginés (1997) indicate that runoff from an 

urbanized area represented 75 percent of the annual 

rainfall amount, as compared to an area mostly in 

secondary forest, which had a runoff of only 36 

percent. Thus, if such conditions are extrapolated to 

the Manatí-Vega Baja area, areal recharge to the upper 

aquifer from urbanized areas in enclosed topographic 

depressions could increase from 20 in/yr to as much as 

42 in/yr, due to additional runoff directed to the 

aquifer.
Hydrogeologic Setting 27

Figure 13. Location of surficial drainage areas along the southern boundary of the upper aquifer, North Coast Province, 

Puerto Rico (see figure 3 for location in the Manatí-Vega Baja study area).
28 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Discharge to Springs

In addition to ground-water discharge to Laguna 

Tortuguero, numerous springs and seeps are reported 

in the coastal wetland areas. Major springs are located 

near Vega Baja (Ojo de Agua), south of Laguna 

Tortuguero, near the junction of Highway PR-2 and 

Río Grande de Manatí (Ojo de Guillo), and Tierras 

Nuevas Poniente (Mamey) (Springs 3, 4, 15, 27, and 

106; fig. 5 and table 1). These third-order diffuse-type 

springs have base flows ranging from 1 to 6 ft3

/s 

(Rodríguez-Martínez, 1997). An instantaneous 

discharge measurement of 2.3 ft3

/s was obtained for 

the springs south of the lagoon near the inflow channel 

to Laguna Tortuguero during a relatively dry period in 

August 1997 (fig. 3). Springs in the municipios of 

Manatí and Vega Baja contributed substantially to for 

public water supply, providing 0.4 Mgal/d in 1959 

(Arnow and Crooks, 1960).

Confining Unit within the North Coast Limestone 

Aquifer System

According to Rodríguez-Martínez (1995), the 

confining unit to the lower aquifer between Manatí 

and Vega Baja consists not only of the upper member 

of the Cibao Formation, but also includes the 

underlying Quebrada Arenas and the Río Indio 

Limestone Members of the Cibao Formation, and the 

informally named mudstone unit (figs. 5, 7, and 8). 

The total thickness of these units at test wells NC-4 

and NC-14 was 991 and 837 ft, respectively. The 

upper member of the Cibao Formation maintains a 

relativel constant thickness of about 165 ft from the 

Río Grande de Manatí to the east of study area 

(Monroe, 1980). 

Giusti (1978) estimated an average hydraulic 

conductivity of 1.4 ft/d for the Cibao Formation in the 

Manatí-Tortuguero area. This estimate, however, is 

thought to be based on pumping tests for wells 

screened or open to the upper member of the Cibao 

Formation and units above. No wells open to only the 

upper member of the Cibao Formation are known to 

exist. Hydraulic conductivity values from slug tests at 

the Vega Alta Superfund Site (located east of Vega 

Baja), conducted in the upper member of the Cibao 

Formation, range from 0.005 to 1 ft/d, within an area 

where the confining unit is considered leaky 

(Geraghty & Miller, 1992). 

Lower North Coast Limestone Aquifer

The lower aquifer is contained within the 

Montebello Limestone Member of the Cibao 

Formation and the Lares Limestone (figs. 5 and 8). 

The lower aquifer was found to contain ground water 

under artesian conditions in 1968, when two industrial 

waste injection wells were drilled in the Cruce Dávila 

area of Barceloneta (Giusti, 1978). The lower aquifer 

is hydraulically separated from the upper aquifer in the 

study area by the upper member of the Cibao 

Formation. The lower aquifer has been developed as a 

source of water for industrial use in the municipios of 

Barceloneta and Manatí. 

SIMULATION OF GROUND-WATER FLOW IN THE 

UPPER AQUIFER

The USGS MODFLOW computer code was 

used previously to simulate two-dimensional flow in 

the upper aquifer in the North Coast Limestone aquifer 

system at Barceloneta (Torres-González, 1985), Vega 

Alta (Gómez-Gómez and Torres-Sierra, 1988), 

Aguadilla to Río Camuy (Tucci and Martínez, 1995), 

and at the Río Camuy to Río Grande de Manatí area 

(Torres-González and others, 1996) (fig. 14). The 

potentiometric-surface map of March 1995 was used 

as a starting point for the conceptualization and 

construction of the model of the upper aquifer within 

the study area (fig. 12). The area modeled was 

extended further west and east to simulate the 

interaction between major streams and the upper 

aquifer. A steady-state simulation was calibrated to the 

observed hydrologic conditions for March 1995 along 

with an additional steady-state simulation for 1940 

hydrologic conditions. A transient simulation was 

initiated for 1940 conditions with the historical 

pumping simulated in 10 stress periods up to 1995. 

The aquifer heads generated for the transient 

simulation were compared to the calibrated steadystate model for March 1995.
Simulation of Ground-Water Flow in the Upper Aquifer 29 Figure 14. Areas in which digital ground-water flow models have been developed in the North Coast Limestone aquifer system, Puerto Rico.
30 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Model Assumptions

One of the principal requirements in using 

MODFLOW is that Darcy’s law is applicable to 

calculate the flux between each finite difference cell. 

This equation is valid for ground-water flow problems 

if the velocity is slow and laminar. The equation is not 

valid for turbulent flow through caverns and 

dissolution channels or conduits. In the case of the 

upper aquifer, the secondary porosity of the Aymamón 

Limestone is high and it is probable that preferential 

flow paths and conduits exist. The high variability in 

transmissivity recorded in selected wells (fig. 10) 

probably results from individual wells tapping 

different fracture zones and dissolution channels.

In order to model a system where caverns and 

dissolution channels exist, “a simplification is to 

assume laminar flow everywhere and an effective 

transmissivity that is uniform throughout each cell of 

the model such that conservation of mass is preserved 

along with known hydraulic gradients” (Kuniansky 

and Holligan, 1994). This simplification is justified, 

since the principal purpose of the model is to improve 

our knowledge of the water balance for the upper 

aquifer by simulating various hydrologic conditions 

and scenarios brought about by hydrologic 

modifications to the flow system, such as dewatering 

wetlands and aquifer withdrawals. 

The USGS MODFLOW-96 computer model 

code (Harbaugh and McDonald, 1997) was used to 

simulate ground-water flow in the unconfined upper 

aquifer. The computer code uses finite-difference 

techniques to solve the water-balance equations for 

ground-water flow within the aquifer, taking into 

consideration sources (primarily recharge from rainfall 

infiltration and seepage from surface-water bodies), 

sinks (primarily discharge to surface-water bodies, 

evapotranspiration, or wells), and change in storage 

(water-level changes). MODFLOW can be used for 

three-dimensional analysis, and for steady or transient 

flow in anisotropic and heterogeneous ground-water 

flow systems. For the purpose of this study, the upper 

aquifer was simulated as a two-dimensional system. 

Model assumptions included that ground-water flow 

through the upper aquifer is predominantly horizontal, 

fluctuations in aquifer head are not sufficient to alter 

the saturated thickness, and the lower aquifer is 

hydraulically independent from the upper aquifer due 

to the confining unit. The unconfined upper aquifer 

was simulated as a confined system, because the 

saturated thickness is relatively constant, thus the 

transmissivity is assumed constant. 

Prior to defining the boundary conditions for the 

model, the following general assumptions were made:

1. Aquifer transmissivity values assigned are 

independent of water-table changes in transient 

simulations. This assumption can be justified 

because ground water throughout the major part of 

the aquifer occurs through preferential horizontal 

flow planes (zones in which the hydraulic 

conductivity is substantially higher), possibly as 

the result of preferential dissolution of the 

hydrogeologic units along the water-table plane of 

previous sea level stands. These zones of high 

hydraulic conductivity were documented within the 

upper aquifer in the Vega Alta area (Gómez-Gómez 

and Torres-Sierra, 1988). At Vega Alta, a high 

hydraulic conductivity zone was documented 

between 70 to 120 ft below mean sea level. This 

zone represents 33 percent of the estimated 

transmissivity in that area.

2. The saltwater/freshwater boundary is a sharp 

interface and static beneath the freshwater part of 

the aquifer. Although known to have changed, the 

effect is most important to ground-water quality 

variations across the aquifer thickness, and less 

important in water-balance computations.

3. The aquifer is at equilibrium under the hydrologic 

conditions used as initial conditions of March 1995 

(fig. 15). This assumption is least certain within the 

area directly south of Laguna Tortuguero, as 

evidenced by the cone of depression along 

Highway PR-2 (Renken and Gómez-Gómez, 1994) 

and the inland displacement of the potentiometric 

surface within the western part of the Manatí 

quadrangle, where ground-water withdrawals have 

increased substantially.

4. Areal rainfall/runoff recharge rates are maintained 

constant for the simulation period. Rainfall 

intensities sufficient to induce recharge and runoff 

occur primarily in a stochastic manner, and is most 

important during the wetter months of the year. 
Simulation of Ground-Water Flow in the Upper Aquifer 31

For long-term simulation, as is the case in this 

analysis, partitioning of rainfall recharge rates as 

a function of measured rainfall is not merited.

5. Stream stages remain constant. This is not a 

sensitive parameter, since the annual variation in 

stage of the two major streams at the gaging-station 

sites between the 90th percentile of flow (base flow 

conditions) and the 10th percentile of flow (flood 

stage conditions) is 3 ft for the Río Grande de 

Manatí and 0.8 ft for the Río Cibuco, and the 

following assumption (6) holds.

6. Ground-water withdrawal rates, as reconstructed 

from available records, are constant for the given 

length of the stress periods used. This assumption 

is generally acceptable since most ground-water 

withdrawals in the area are for public water-supply 

purposes, and such wells operate at relatively 

constant discharge rates.

All properties assigned to each cell represent 

average values in the area of that cell. To run the 

model, parameters must be assigned for initial 

conditions that should represent, as nearly as possible, 

steady-state conditions within the aquifer (inflow 

equals outflow with no change in storage). Input 

parameters must be provided for the starting heads, 

transmissivity, rates of areal aquifer recharge from 

rainfall/runoff infiltration, streambed/seabed 

conductance, and ground-water withdrawals. Under 

ideal conditions, the best representation of steady-state 

conditions in the model area was that which existed 

prior to dredging of an ocean outlet connecting 

Laguna Tortuguero with the Atlantic Ocean in 1943, 

when aquifer development was negligible. No data 

exist, however, on the distribution of the 

potentiometric surface or hydrologic fluxes prior to 

this date. The alternate option available for assignment 

of aquifer properties is to assume that aquifer 

conditions during March 1995 (only reference date for 

which data are available on potentiometric-surface 

distribution, ground-water withdrawal rates, and 

discharge at the Laguna Tortuguero outlet) are 

representative of steady-state conditions under the 

estimated aquifer water balance.

Figure 15. Hydrograph of ground-water levels at well 105 (Cantito La Luisa), Manatí area, 

Puerto Rico (refer to figure 6 for well location).
32 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Grid Design and Boundary Conditions

A model grid was designed with the columns 

generally oriented parallel to the direction of groundwater flow or head gradient, in the north-south vector 

with grid blocks (1,000 X 1,000 ft) divided into 36 

rows and 73 columns (fig. 16). Although the altitude 

of the bottom of the aquifer is not essential in the 

two-dimensional code of MODFLOW, in this case, 

the bottom of the aquifer corresponds to the top of 

the upper member of the Cibao Formation from the 

southern model boundary to the area, where the upper 

aquifer attains a maximum thickness of 450 ft (fig. 9). 

North of this line, the lower boundary of the upper 

aquifer is delimited by the saltwater/freshwater 

interface. The southern boundary of the ground-water 

flow model was established at latitude 18°24’, to 

include aquifer recharge originating from rainfall 

infiltration at outcrops of the Aguada Limestone. The 

southern boundary is represented as a no-flow 

boundary, except where runoff over the Cibao 

Formation occurs, a hydrologic condition represented 

in the model by injection wells located in rows 33 to 

36. The western and eastern edges of the model area 

are no-flow boundaries beyond the Río Grande de 

Manatí to the west and the Río Cibuco to the east. 

These boundaries were extended beyond the rivers to 

simulate the surface-water/ground-water interaction in 

the area of the rivers, and to minimize computational 

errors resulting from the effects of model boundaries.

Internal Boundaries

The interaction between streams and the aquifer 

was modeled by using the River Package (McDonald 

and Harbaugh, 1988) in the model cells for which 

exchange of water exists (part of stream course for 

which data are available showing gaining or losing 

reaches) or is suspected (such as the estuary parts of 

streams and drainage channels in wetland areas that 

are not gaged). Riverbed conductance is defined in 

MODFLOW as: 

C = (Kz/m) x (L) x (W),

where

Kz is the streambed vertical hydraulic 

conductivity,

m is the thickness of the riverbed,

L is the length of the stream segment within 

the model cell area, and

W is the average width of the stream segment.

Since Kz/m is generally unknown for most 

conditions, C is determined indirectly by varying the 

value as part of the model calibration process. 

Modeled streamflow gains (discharge from aquifer) or 

losses (recharge from stream) are compared with 

observed data for segments where data are available. 

Model calibration is achieved by matching modeled 

gains and losses in the stream with observed data, and 

by matching modeled heads at and near the stream 

with observed water levels in the aquifer. Flow 

between the stream and the aquifer is governed by the 

conductance of the riverbed and the relation between 

stage in the stream and head in the aquifer, as 

described in the equation:

Q = C x [Hs – Ha],

where

Q is the flow between the stream and the 

aquifer, taken as positive if directed into 

the aquifer,

C is the hydraulic conductance of the streamaquifer interconnection,

Hs is the assigned head value for the water 

surface in the stream segment, and

Ha is the input aquifer head value for the 

model cell.

For stream segments where no streamflow gain 

or loss data are available, the conductance values are 

assigned indirectly by trial and error until the modeled 

areal head distribution is in general agreement with the 

input calibration potentiometric-surface distribution. 
Simulation of Ground-Water Flow in the Upper Aquifer 33 Figure 16. Model grid and boundary conditions of the upper aquifer in the Manatí-Vega Baja study area, North Coast Province, Puerto Rico.
34 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

The River Package was also used to simulate the 

interaction between the upper aquifer and Laguna 

Tortuguero. The seabed along the coast of the Atlantic 

Ocean was represented as a streambed with a head of 

0.0 ft. The head gradient of the aquifer along the coast 

was sufficient to avoid the adverse impact of artificial 

input into the model from river cells. The high 

gradient between the upper aquifer near Laguna 

Tortuguero and the Atlantic Ocean during 1940 

conditions required moving the boundary north near 

Puerto del Tortuguero. This is also in general 

agreement with reported offshore springs in the area.

The model input requirements in MODFLOW 

for simulating streams are the head in the stream, Hs, 

riverbed conductance, and riverbed bottom elevation. 

The head is computed by taking the streambed altitude 

values estimated from 1:20,000 scale topographic 

maps and field observations, and adding a value of 

stream depth ranging from 0.2 to 1.1 ft. Initial riverbed 

conductance values were taken from other models for 

the Río Grande de Manatí (Torres-González and 

others, 1996) and the Río Cibuco (Gómez-Gómez and 

Torres-Sierra, 1988). The riverbed conductance values 

for the Río Cibuco were also used for the Río Indio 

and adjusted according to the aquifer gains and losses 

recorded during seepage runs made between the 

bridge at Highway PR-674 (Río Arriba) north to the 

overpass at Highway PR-22. The riverbed 

conductance values for Laguna Tortuguero were 

assigned by using an estimated vertical hydraulic 

conductivity multiplied by the cell dimensions. The 

stage level for Laguna Tortuguero of 0.9 ft was 

surveyed for the work conducted in March 1995 

(Conde-Costas and Rodríguez, 1997). The number of 

river cells assigned for Laguna Tortuguero were based 

on the computed area. The ground-water fluxes to the 

lagoon were estimated from previous studies (Bennett 

and Giusti, 1972) and monthly discharge 

measurements taken at USGS gaging station 

50038200. 

The major springs in the study area were 

simulated using the Drain Package within 

MODFLOW (McDonald and Harbaugh, 1988). The 

model input requirements for this package include the 

elevation of the spring or seep and a conductance 

value. If the head in the aquifer is lowered below the 

specified drain elevation, then there is no exchange 

between the aquifer and the drain (spring) is dry. The 

location of the third-order diffuse-flow springs where 

the drain package was used is shown in figure 16. The 

spring elevation values were estimated from 1:20,000 

scale topographic maps and Ojo de Agua near Vega 

Baja (fig. 16) was referenced to mean sea-level datum 

using third-order leveling (Conde-Costas and 

Rodríguez, 1997).

Simulated Recharge and Discharge

Using the mass-balance approach, a maximum 

aquifer recharge rate for the karst terrain in northern 

Puerto Rico was established at 20 to 25 in/yr (Bennett 

and Giusti, 1976). The remaining 40 to 50 in/yr from 

the average yearly rainfall of 60 to 75 in/yr is 

conveyed by evapotranspiration. Ground-water flow 

models constructed for the North Coast Limestone 

aquifer system have used varying maximum rates of 

ground-water recharge to the upper aquifer: 17.5 in/yr 

(Geraghty & Miller, 1992), 19.5 in/yr (Gómez-Gómez 

and Torres-Sierra, 1988), 19.7 in/yr (Heisel and others, 

1983), 20 in/yr (Torres-González and others, 1996), 

22 in/yr (Tucci and Martínez, 1995), and 25 in/yr 

(Torres-González, 1985). Initially for the steady-state 

model, the recharge rate for areas with closed 

depressions or areas with poorly defined surface-water 

drainage was assigned a maximum value of 18 in/yr 

(fig. 17). 

The rainfall/runoff recharge at outcrop areas 

south of latitude 18°25’ are based on regular discharge 

measurements made along the Quebrada Hicatea for a 

1-year period. As an initial input, the recharge south of 

latitude 18°25’ was estimated to be 8 in/yr, which is 

slightly greater than the maximum estimate of 6 in/yr 

calculated for the Quebrada Hicatea for the period 

from June 1997 to May 1998, which was measured 

under drier-than-normal conditions. The 8 in/yr of 

rainfall/runoff recharge along the area south of 18°24’ 

was simulated using injection wells near the southern 

model boundary (fig. 16). The estimated discharge 

along Quebrada Hicatea of 0.5 ft3

/s was used to 

estimate inflow for drainage areas with similar 

characteristics to the west (figs. 13 and 16). The total 

flux to the aquifer from surficial drainage over the 

Cibao Formation in its outcrop area to the upper 

aquifer along the southern boundary of the model was 

estimated to be equivalent to an injection rate of 

1.6 ft3

/s. 
Simulation of Ground-Water Flow in the Upper Aquifer 35Figure 17. Calibrated recharge distribution used for the digital ground-water flow model simulations of the upper aquifer system in the 

Manatí-Vega Baja study area, North Coast Province, Puerto Rico.
36 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

A minimum recharge of 2 in/yr was applied to 

the modeled alluvial valley of the Río Grande de 

Manatí north of Highway PR-2, and 4 in/yr in other 

areas having substantial alluvial deposits. These 

relatively low recharge valves were used, since most 

rainfall infiltration in the alluvial valleys is probably 

discharge rapidly to streams. This condition represents 

a local flow system, and the recharge does not reach 

the upper aquifer.

Ground-water withdrawal rates assigned in 

model cells for initial conditions correspond to the 

pumpage rates documented for hydrologic conditions 

in March 1995 and the potentiometric-surface map 

prepared by Conde-Costas and Rodríguez (1997) 

(fig. 12). The ground-water withdrawal rates used for 

the transient model simulation correspond to the 

historical pumpage rates reconstructed from PRASA 

public water-supply and the PRDNER records, and the 

USGS water-use database, which includes production 

data for industrial, public water-supply, and irrigation 

uses. The reconstructed ground-water withdrawal 

estimates and stress periods used in the transient 

simulation are given in figure 18 and table 2. Springs 

within the modeled area were simulated using the 

drain package in cells where springs are located. The 

total discharge for the springs were obtained from 

previous studies: the flow rate for the springs south of 

Laguna Tortuguero was estimated to range between 6 

and 8 ft3

/s, based on a ground-water model developed 

for a proposed harbor construction project (Bennett 

and Giusti, 1972); estimates of flow rates used in the 

model calibration process for Ojo de Guillo, 

Mameyes, Isidora springs in the lower Río Grande de 

Manatí, and Ojo de Agua spring at Vega Baja are from 

Gómez-Gómez (1984), Guzmán-Ríos (1988), and 

Rodríguez-Martínez (1997), in addition to field 

verification measurements made during the study. The 

spring discharge rates were used in adjusting the drain 

conductance values, as part of the model calibration 

process.

Figure 18. Ground-water withdrawal rates used for each stress period for the transient simulations, ManatíVega Baja model area, North Coast Province, Puerto Rico (see table 2 for individual well pump rates used).
Simulation of Ground-Water Flow in the Upper Aquifer 37

Table 2. Ground-water withdrawal rates used for the Manatí–Vega Baja transient simulation for each stress period[PS, public supply well; Ind, industrial supply well; Irr, irrigation well; Mn, mining well; NA, information unavailable; Mgal/d, million gallons per day]

Well name Year drilled Use of water Stress period and associated withdrawal rate in Mgal/d 1 1943-45 2 1946-60 3 1961-65 4 1966-70 5 1971-75 6 1976-79 7 1980-81 8 1982-84 9 1985-90 10 1991-95

Ceiba 1 1931 Irr 0.078 0.079 0 0 0 0 0 1.15 0 0Ceiba 2 Carmelita 1931 Irr 0.078 0.079 0 0‘pO 0 0 0 0 0 0Santa Rosa NA PS 0.078 0.078 0.634 0.634 0.634 0.634 0.634 0.634 0 0Campo Alegre 1930 PS 0.1 0.1 0 0 0 0 0 0 0 0Rice Program 3 1934 Irr 0.078 0.078 0 0 0 0 0 0.72 0 0Central San Vicente 1932 Ind 0.15 0.15 0.15 0 0 0 0 0 0 0Tortuguero 1 1940 PS 0.1 0.1 0.1 0 0 0 0 0.09 0 0Tortuguero 2 1940 PS 0.1 0.1 0.1 0 0 0 0 0 0 0Tortuguero 3 1940 PS 0.1 0.1 0.1 0 0 0 0 0 0 0Fortuna 1930 PS 0.078 0.3 0.3 0.4 0.52 0.52 0.52 0.52 0.18 0.33Manatí 1 1947 PS 0.3 0.3 1.0 1.1 1.1 1.1 1.3 1.17 1.03Manatí 2 1947 PS 0.3 0.3 1.0 1.0 1.0 1.0 1.2 1.0 0.95Vega Baja 1 1948 PS 0.1 0.15 0.36 0.36 0.36 0.36 0.36 0.32 0.17Coto Norte 1 1947 PS 0.04 0.1 0.28 0.28 0.28 0.28 0.28 0 0Pugnado Afuera 1 1950 PS 0.05 0.2 0.5 0.5 0.5 0.5 0.5 0.5 0.45China Caribe 1952 PS 0.05 0.05 0 0 0 0 0 0 0Kirk Wing 1954 Ind 0.06 0.06 0 0 0 0 0 0 0Cubano Jacinto 1956 Irr 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05Sabana Hoyos 1 1959 PS 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.5Agregado 1960 Mn 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.28Coto Norte 2 1966 PS 0.19 0.19 0.19 0.19 0.19 0.04 0Coto Sur 1 1967 PS 0.64 0.7 0.8 0.8 0.8 0.66 0.92Warner Lambert 1 1967 Ind 0.045 0.045 0.045 0.045 0.045 0.045 0.08Oficina PRASA 1968 PS 0.3 0.6 0.6 0.6 0.6 0.7 1.03Vega Baja 2 1969 PS 1.0 1.0 1.0 1.0 0.44 0.54Sabana Hoyos 2 1969 PS 0.1 0.1 0.1 0.1 0.07 0.3Vega Baja 3 1970 PS 1.0 1.2 1.2 1.3 1.3 1.28Schering Plough 1 & 2 1970 Ind 0.3 0.6 0.7 0.72 0.6 0.66Sabana Hoyos 3 1971 PS 0.1 0.2 0.2 0.2 0.2 0.2Almirante 2 1971 PS 0.1 0.12 0.12 0.12 0.12 0.12
38 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico Coto Sur 2 1971 PS 0.2 0.24 0.24 0.24 0.17 0 Warner Lambert 2 1971 Ind 0.045 0.045 0.045 0.045 0.045 0.08 Davis & Geck N & S 1974 Ind 0.1 0.2 0.2 0.24 0.25 0.25 Eaton Labs 1974 Ind 0.07 0.07 0.07 0.07 0.07 0.07 Inland Chemical 1974 Ind 0.2 0.6 0.6 0.6 0.58 0.43 Coto Sur 3 1974 PS 0.2 0.53 0.6 0.75 0.51 0 Roche 1974 Ind 0.14 0.14 0.14 0.14 0.16 Boquillas 1978 PS 0.13 0.52 0.53 0.45 0.43 Rabano 1979 PS 0 0.2 0.32 0.45 0.42 Coto Sur 4 1979 PS 0.1 0.27 0.26 0.23 0.18 Almirante 3 1979 PS 0.08 0.1 0.23 0.19 0.16 Alturas 1980 PS 0 0.64 0.7 0.6 0.58 Pugnado Afuera 2 1980 PS 0 0.5 0.51 0.54 0.5 Coto Norte 3 1980 PS 0 0.12 0.13 0.14 Monserrate 1982 PS 0.35 0.7 1.11 0.66 Pugnado 3 1981 PS 0.12 0.23 0.16 0 Vega Baja 4 1984 PS 0 0.57 0.54 Ortho Lab 1984 Ind 0 0.02 0.07 Atenas 1984 PS 0.05 0.15 0.2 Sobrino 1983 PS 0.18 0.3 0.31

Coto Sur 5 1984 PS 0.23 0.38 0.32Coto Sur 6 1984 PS 0.42 0.53 0.48Algarrobo 1988 PS 0 0.7Cruz Rosa-Rivas 1989 PS 0 0.25Cordova Davilla 1989 PS 0.7 0.78Villa Pinares 1989 PS 0 0.3Escal Fullery 1989 PS 0 0.26Arraiza 1991 PS 0 0.14Total in Mgal/d 1.94 4.114 6.264 6.069 10.064 12.104 14.664 19.11 16.34 17.3

Table 2. Ground-water withdrawal rates used for the Manatí–Vega Baja transient simulation for each stress period—Continued

Well name Year drilled Use of water Stress period and associated withdrawal rate in Mgal/d

1

1943-45

2

1946-60

3

1961-65

4

1966-70

5

1971-75

6

1976-79

7

1980-81

8

1982-84

9

1985-90

10

1991-95
Simulation of Ground-Water Flow in the Upper Aquifer 39

Model Calibration Process

The steady-state model was calibrated to 

assumed conditions and the observed potentiometric 

surface during March 1995 (Conde-Costas and 

Rodríguez, 1997). The heads in Laguna Tortuguero 

were set to the surveyed elevation of 0.9 ft above mean 

sea level for the river package. The lagoon outlet 

channel was simulated using river nodes with a change 

of head from 0.9 ft at the lagoon to 0.0 ft at the ocean 

(corresponding to mean sea level datum). The model 

calibration process required making adjustments to 

recharge values, first by changing the conversion 

factor in the recharge data-input matrix, and then by 

local adjustment of both transmissivity and recharge, 

until the following conditions were met: (a) modelgenerated heads and the potentiometric surface 

approximated those given in the hydrologic conditions 

of March 1995; (b) flux to cells representing springs 

(drain package) approximated observed flow rates in 

1997; and (c) the flux to Laguna Tortuguero via direct 

discharge to the lagoon and nearby springs 

approximated the flow observed at the ocean outlet 

(50038200) in 1997. 

During the steady-state model calibration 

process it was necessary to make some minor 

adjustments to modeled transmissivity input and 

recharge values. The final calibrated values for 

transmissivity were in general agreement with the 

areal distribution derived from specific-capacity data, 

and the aquifer flux was achieved with recharge of 

18 in/yr or less, which is in general agreement with 

adjusted values for other areas previously modeled 

(figs. 17 and 18). The total net aquifer recharge 

simulated with the calibrated steady-state flow model 

of the upper aquifer was 35.9 ft3

/s. The ground-water 

budget for the Manatí to Vega Baja area, computed by 

Bennett and Giusti (1976), using the mass-balance 

approach, is 43.8 ft3

/s. Flow rates in the Laguna 

Tortuguero outlet channel and springs were also 

closely approximated, with the exception of Mameyes 

and several smaller springs in Barrio Tierra Nuevas, 

north of Manatí.

Riverbed conductance values were adjusted 

during the steady-state calibration process, in order to 

match low-flow measurements taken along the Río 

Grande de Manatí and the Río Indio. Discharge 

measurements made during the low-flow period in 

July 1997 were used in the comparison. The riverbed 

conductance values were adjusted along a section of 

the Río Grande de Manatí corresponding to model 

cells row 33, column 19, northward to row 28, column 

19 (appendix 1). A simulated loss of 5.8 ft3

/s closely 

approximated the 5 ft3/s low-flow river loss obtained 

on July 9, 1997. Several low-flow seepage runs were 

conducted along the Río Indio between the Highway 

PR-674 bridge (Río Arriba) and the overpass at 

Highway PR-22, south of the PRASA filtration plant. 

Although all flow measurements indicate a net rivergain for this stretch, measurements made on May 6, 

1997, show a loss from the river to the aquifer of about 

1 ft3

/s between row 27, column 61, and row 24, 

column 60. The steady-state model calibration for 

1995 conditions indicates a streamflow loss of 1.0 ft3/s 

to the aquifer for the river-reach north of Highway 

PR-674 to Highway PR-22, and a loss of 2.6 ft3/s from 

the Río Cibuco, primarily in the river reaches south of 

Highway PR-2. 

An instantaneous discharge measurement of 

2.3 ft3

/s was obtained for the springs south of the 

lagoon near the inflow channel to Laguna Tortuguero 

during a relatively dry period in August 1997. The 

1995 steady-state calibrated model output was 2.4 ft3

/s 

in cells representing the springs south of Laguna 

Tortuguero (table 2). The simulated discharge values 

for Ojo de Agua of 2.0 ft3

/s compared well with the 

range (1.4 to 5.9 ft3

/s) of discrete discharge 

measurements made between 1993 and 1996 

(Rodríguez-Martínez, 1997). The simulated discharge 

values for Ojo de Guillo of 2.2 ft3

/s compared 

favorably with the 2.0 ft3

/s base flow established for 

the study of the Lower Río Grande de Manatí in 1984 

(F. Gómez-Gómez, USGS, written commun., 1999).

The calibrated model heads were compared to 

actual conditions using the measured heads reported 

by Conde-Costas and Rodríguez (1997). The results 

indicate that 36 of a total of 37 control cell locations 

(water-level measurement sites) were calibrated within 

10 ft of the measured heads. The difference between 

simulated and measured heads was greatest in the 

Coto Sur area, probably due to a relatively large model 

cell size compared to the steep head gradient in this 

area (appendix 2). South of latitude 18°25’, the low 

transmissivity values result in large fluctuations in 

aquifer heads over time and a steep gradient of the 

potentiometric surface. This is evident in observed 

water-level fluctuations of approximately 50 ft in the 

Perica observation well. Heads in six of the seven 
40 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

simulated wells were within 5 to 18 ft of the measured 

values in the area located between the Coto Sur area 

and the southern model boundary (fig. 19). In general, 

the difference between measured and simulated heads 

is less than 2 ft in the coastal plain north of Highway 

PR-2.

Simulated Change at Laguna Tortuguero 

1940 to 1995

After the model was calibrated for steady-state 

conditions in March 1995, another steady-state 

simulation was used to document 1940 conditions, 

prior to dredging of the ocean outlet channel in 1943. 

The primary difference between the 1995 and 1940 

model conditions were that for the 1940 model run, a 

water level of 3.3 ft above mean sea level was used for 

the river nodes representing the lagoon, and the three 

river nodes used to simulate the outlet channel to the 

sea were eliminated. Also, ground-water withdrawals 

for 1940 conditions were estimated to be 0.98 ft3

/s 

(0.63 Mgal/d). Adjustments to transmissivity values 

were not made, with the assumption that changes in 

the thickness of the freshwater lens in the coastal part 

of the aquifer were not great enough to alter the 

aquifer transmissivity estimates used in the steadystate model. A comparison of the 1940 simulation to 

the aquifer heads generated for March 1995 

hydrologic conditions (Conde-Costas and Rodríguez, 

1997) reveals the largest change in aquifer heads 

occurred in the Coto Sur area (well 78; fig. 5); heads 

changed from approximately 30 ft to less than 10 ft 

(figs. 20 and 21, respectively). The simulated heads 

for steady-state conditions for 1940 were used as 

initial heads for the three transient simulations. 

Because the majority of the ground-water 

development for the Manatí-Vega Baja area took place 

during the 1970’s, the overall ground-water budget 

estimates of Giusti (1978) can be applied to the Manatí 

ground-water flow model for the upper aquifer steadystate 1940 conditions.

Aquifer outflows at springs, wetland areas, and 

river reaches in the coastal plains show a substantial 

decline from 1940 to 1995. The decreased outflows 

are attributed to increased ground-water withdrawals 

from a simulated rate of 0.98 ft3

/s during 1940 

conditions, to 26.4 ft3

/s during 1995. The areal 

recharge values were the same for both simulations, 

but the increased ground-water withdrawals induced 

an additional 6.9 ft3/s from river seepage, for an 

overall inflow of 48.6 ft3

/s. 

Additional Calibration

Validation of the ground-water flow model was 

accomplished by simulating the historical trend of 

ground-water development in the area from 1943 to 

1995. This transient simulation was divided into 10 

stress periods of varying durations governed by 

substantial changes in pumpage (fig. 18). The results 

were compared to the head data obtained by CondeCostas and Rodríguez (1997). The construction of the 

outlet channel of Laguna Tortuguero in 1943 was 

chosen as the initial date for the transient simulation. 

The aquifer heads from the steady-state 1940 

simulation were used as the starting heads for the 

transient simulation, and the upper aquifer was 

assigned a storage coefficient of 0.10. The river-stage 

elevation and riverbed conductance remained constant 

throughout the simulation, with the exception of the 

stage estimates for Laguna Tortuguero, which were 

altered from a high of 3.3 ft (1 meter) pre-1943, 1.5 ft 

in 1975, and 0.9 ft above mean sea level in 1995. Also, 

riverbed conductance, transmissivities, and areal 

recharge remained constant throughout the transient 

simulation. Historical pumpage was reconstructed 

using available data from various sources, with the 

assumption that a given well started pumping from the 

construction date, unless available information 

indicated otherwise (table 3). 

The aquifer heads for the 1995 transient 

simulation were slightly higher than the 1995 steadystate simulation, with an average absolute deviation 

from observed heads of 3.17 ft, compared to 3.10 ft for 

the steady-state model. The ground-water withdrawal 

rates for stress period 8 include four wells near the 

Río Cibuco reactivated as part of the Rice Irrigation 

Program; withdrawals from these wells totaled 

3 Mgal/d (Fernando Gómez-Gómez, USGS, written 

commun., 1999). A comparison of the measured 

Laguna Tortuguero outflow (station number 

50038200) to simulated values is shown in figure 22. 

A slight decline is evident in both the measured and 

the computed ground-water flux at the end of each 

stress period, which is attributed to increased groundwater withdrawals for the period of record.
Hydrogeologic Setting 41

Figure 19. Calibrated transmissivity distribution for the digital ground-water flow model simulations of the upper aquifer in the ManatíVega Baja area, North Coast Province, Puerto Rico.
42 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 20. Simulated potentiometric surface for March 1995 steady-state conditions in the Manatí-Vega Baja study area, North Coast 

Province, Puerto Rico.
Hydrogeologic Setting 43 Figure 21. Simulated potentiometric surface for 1940 steady-state conditions in the Manatí-Vega Baja study area, North Coast Province, 

Puerto Rico.
44 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Sensitivity Analysis

As with any model, there is uncertainty in the 

measurements of head (datum errors), transmissivity, 

estimation of recharge, and well withdrawal rates; 

therefore, it needs to be shown what effect there would 

be in a model if a parameter was not simulated 

properly. Moreover, each given input variable 

(transmissivity, riverbed conductance, recharge, and 

well pump rates) was adjusted during the calibration 

process to achieve a best fit of aquifer heads and 

fluxes, but the combination of parameters does not 

produce a unique solution. Therefore, values of 

transmissivity, recharge, ground-water withdrawals, 

and riverbed conductance, were factored separately by 

0.25, 0.5, 0.75, 1.25, and 1.5 times, while the effects 

on the system were noted by observing changes in 

aquifer heads and water-budget components 

(appendixes 1 and 2). The mean residual or the 

accumulated deviation from the measured control cells 

was totaled and divided by the number of 

measurement sites for each recorded change. 

The results of the sensitivity analysis show the 

ground-water model is slightly more sensitive to 

changes in transmissivity than changes in net recharge 

(fig. 23). When the input riverbed conductance values 

were increased by a factor of 10, the aquifer heads 

were altered only slightly, but the hydrologic budget 

increased from 45.8 to 54.9 ft3

/s, due to increased river 

seepage to the upper aquifer. Other parameters were 

also changed, using multipliers of 0.25, 0.5, 0.75, 1.25, 

and 1.5, and the results are presented in appendix 2 

along with the percentage of heads that were within a 

given margin from the measured control nodes. In 

general, the aquifer heads in coastal areas were less 

sensitive to changes in transmissivity whereas heads in 

the upland areas south of Highway PR-2 were more 

sensitive, due to lower hydraulic conductivities and 

decreased aquifer thickness. Increasing transmissivity 

values from 1.25 to 2 times the calibrated values 

induced additional river flow into the aquifer ranging 

from approximately 1 to 4 ft3

/s.

Figure 22. Comparison of measured and simulated discharge at Laguna Tortuguero outflow site.
Hydrogeologic Setting 45

Table 3. Comparison of simulated steady-state ground-water budgets for 1940 and March 1995 

hydrologic conditions, Manatí-Vega Baja area, North Coast Province, Puerto Rico 

[ft3/s, cubic feet per second]

1940

Simulated flow 

in ft3

/s

1995

Simulated flow

in ft3/s

Inflows:

Quebradas Hicatea and El Salto, and Pugnado Adentro 1.61 1.61

drainage area along southern boundary (injection wells)

River leakage into aquifer:

Río Grande de Manatí 2.74 7.01

Río Cibuco 0.56 2.56

Río Indio 0.91 1.48

Total river leakage: 4.21 11.05

Recharge 35.93 35.93

Total inflows: 41.81 48.59

Outflows:

Ground-water withdrawals 0.98 26.35

Springs: 

Springs - South of Laguna Tortuguero 5.93 2.37

Springs - Mameyes and Tierra Nueva 2.23 0.70

Spring - Ojo de Agua Vega Baja 6.75 2.05

Spring - Ojo de Guillo 2.45 2.21

Total springs: 17.36 7.33

River leakage out of aquifer:

Caño Cabo Caribe 3.44 1.92

Caño Las Pozas 1.76 1.40

Laguna Tortuguero 4.00 2.86

Río Grande de Manatí 8.02 4.94

Río Indio 0.66 0.33

Río Cibuco 3.88 2.90

Atlantic Ocean 1.67 0.57

Total river leakage: 23.43 14.92

Total outflows: 41.77 48.60
46 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 23. Sensitivity of model to changes in transmissivity and recharge.
Hydrogeologic Setting 47

Simulated Effects of Development

The increase in ground-water withdrawals in the 

upper aquifer between 1940 and 1995 had the effect of 

reducing ground-water discharge from springs, 

Laguna Tortuguero, and wetland areas while inducing 

additional recharge from the rivers into the aquifer 

(table 2). The depletion in aquifer storage in the Coto 

Sur area east of Manatí by increased ground-water 

withdrawals has lowered the aquifer head elevations 

from 30 to 10 ft during the same period (figs. 20 and 

21, respectively). 

Effect of Ground-Water Withdrawals on 

Hydrologic System

The total rate of ground-water withdrawals for 

1940 conditions was estimated to be 0.98 Mgal/d, 

primarily along the coastal plain. In the late 1960’s, the 

municipios constructed additional wells, and 

withdrawal rates increased to an estimated 6.1 Mgal/d 

(fig. 18). In the mid-1970’s, a number of industries 

were established in the area that needed additional 

water supplies, and Vega Baja constructed several 

production wells, increasing total ground-water 

withdrawals to 10.1 Mgal/d. Data from the transient 

simulation show a substantial reduction in flow to 

springs at the end of stress period 4 (1970) attributed 

to increased ground-water withdrawals from the 

system. Increased ground-water withdrawals from 

three PRASA wells near Manatí (2.3 Mgal/d) in 1970 

induced additional seepage from the Río Grande de 

Manatí. In the mid 1970’s, the primary area of groundwater development was the Coto Sur area, between 

Highway PR-670 and Highway PR-2, with four 

production wells constructed to supply nearby 

industrial plants. Ground-water withdrawals in this 

area increased from 1.1 Mgal/d in 1970 to 3.0 Mgal/d 

in 1979, reaching a peak of 5.2 Mgal/d in 1984 before 

tapering off to 4.6 Mgal/d in 1990, due to several well 

closures. The effect on the aquifer was to lower the 

heads by as much as 18 ft through depletion of storage. 

According to output from the transient simulation, 

storage of the upper aquifer was depleted by 0.5 

Mgal/d at the end of stress period 8 in 1984. Also 

during stress period 8 (1982-84), an additional 3 

Mgal/d was pumped from four wells near the Río 

Cibuco, as part of a feasibility study to cultivate rice in 

the Río Cibuco valley. These wells were shut down at 

the conclusion of the study, but the construction of 

four PRASA public-supply wells in 1989 has 

maintained ground-water withdrawals at 17.3 Mgal/d.

Projected Changes in Ground-Water Withdrawals

The “Superaqueduct,” when completed, will 

augment ground-water supplies by approximately 

6 Mgal/d (F. Gómez-Gómez, USGS, written commun., 

1999) to the municipios of Manatí and Vega Baja. The 

pipeline will transport approximately 75 Mgal/d of 

water from Lago Dos Bocas to communities along the 

north coast of Puerto Rico and the San Juan 

metropolitan area. The pipeline will pass through the 

municipios of Manatí and Vega Baja, along Highway 

PR-22 and supply water to the surrounding 

communities. Presumably, PRASA will close 

production wells having marginal water quality and 

place them on emergency (drought) stand-by status. A 

transient simulation was run to the year 2010, 

extending from the end of stress period 10 of the 

previously described transient simulation, and placing 

the projected withdrawal rates in three additional 

stress periods of varying duration (fig. 22). It is 

anticipated that well closures will occur gradually, 

until the pipeline is fully operational and integrated 

into the existing distribution system in 2005. Groundwater withdrawals are slightly higher for stress period 

12 than those in stress periods 11 or 13, due to 

additional production wells along the western banks of 

the Río Grande de Manatí being placed on-line 

(capacity 2.3 Mgal/d). These wells (Cortez I and II) 

will supply the Cortez area and connect into the 

distribution system along Highway PR-2. The results 

of the transient simulation (fig. 24) show the 5-ft 

potentiometric contour moving north, and the aquifer 

heads in the Coto Sur area recovering to 

approximately 15 to 20 ft above mean sea level datum, 

with a 6-Mgal/d decrease in ground-water 

withdrawals. All springs in the wetland areas showed 

substantial increases in flow due to the decreased 

pumpage.
48 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Figure 24. Simulated potentiometric surface from transient model runs using 1995 hydrologic conditions and predicted condition for 2010 in 

the Manatí-Vega Baja study area, North Coast Province, Puerto Rico (refer to figure 14 for withdrawal rates and stress periods).
Model Limitations and Additional Data Needs 49

MODEL LIMITATIONS AND ADDITIONAL 

DATA NEEDS

The construction of the Manatí ground-water 

flow model of the upper aquifer furthers our 

understanding of the hydrogeologic system. Largescale changes can be anticipated, such as increased or 

decreased ground-water withdrawals over a given 

area. The calibration of the ground-water flow model 

can be considered a best-fit approximation of the 

known hydrologic parameters. Emphasis should be 

given to the leveling of long-term observation wells 

(Cantito La Luisa and Rosario 2) to improve inherent 

datum errors. Additional seepage runs should be 

conducted in specific areas along the Río Grande de 

Manatí and Río Indio to improve the accounting of 

gains and losses to the aquifer. 

The constructed two-dimensional ground-water 

model does not have a moveable lower boundary, as 

occurs along the freshwater/saltwater interface. 

Improvements to the model could incorporate a 

package to simulate the freshwater/saltwater 

boundary, and use the results of tracer studies to 

define preferential ground-water flow paths to Laguna 

Tortuguero and nearby springs. Additional work 

should be conducted to inventory active domestic 

wells to improve the estimate of domestic groundwater withdrawals and to refine the hydrologic budget 

terms.

SUMMARY

A two-dimensional ground-water flow model of 

the Manatí area was constructed using the USGS 

computer program, MODFLOW, to simulate the 

effects of ground-water development and predict 

future changes to the Upper North Coast Limestone 

aquifer. Steady-state simulations were run for 1940 

and for March 1995 to calibrate the model (because 

sufficient verifying data were available). The aquifer 

heads generated from the 1940 steady-state simulation 

were utilized to initiate a transient simulation with 10 

stress periods up through 1995. The resulting heads 

were then used as initial conditions for a separate 

transient simulation that extended from 1995 to 2010 

in order to predict the effect of the expected decrease 

in ground-water withdrawals on the ground-water 

system. 

Findings from this investigation and model 

construction include:

1. Calibrated transmissivity values ranged from less 

than 500 ft3

/s, just north of the southern boundary, 

to about 70,000 ft3

/s, southwest of Vega Baja.

2. Model-calibrated aquifer recharge values ranged 

from 0 in/yr in the wetland areas of Cabo Caribe, 

to 4 in/yr in the alluvial valleys of Río Grande de 

Manatí and Río Cibuco, and 18 in/yr in sinkholes 

and areas of enclosed depressions.

3. Ground-water influx along the southern boundary 

of the model of 1.6 ft3/s (injection wells) was based 

on flow measurements taken at Quebrada Hicatea 

over a 1-year period.

4. Volumetric budget terms for major ground-water 

flow components from 1940 steady-state 

simulation are:

• areal recharge, 35.93 ft3/s,

• stream-flow infiltration into the aquifer along 

the central portion of the southern boundary 

of 1.61 ft3/s, simulated as injection wells, 

• streamflow infiltration from losing river 

reaches, 4.21 ft3

/s,

• discharge from springs south of Laguna 

Tortuguero, 5.93 ft3

/s, 

• discharge directly to Laguna Tortuguero, 

4.00 ft3

/s, 

• discharge from other springs, 11.43 ft3/s, 

• discharge to the wetland areas northeast of 

Laguna Tortuguero, 5.20 ft3/s, 

• discharge to gaining river reaches, 12.56 ft3/s, 

• discharge to the sea 1.67 ft3/s, 

• discharge to pumping wells, 0.98 ft3/s. 

The total calibrated ground-water flow was 41.77 

ft3

/s.
50 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

5. Volumetric budget terms for major ground-water 

flow components for March 1995 steady-state 

simulation are:

• areal recharge, 35.93 ft3/s,

• stream-flow infiltration into the aquifer along 

the central portion of the southern boundary, 

1.61 ft3

/s, simulated as injection wells,

• streamflow infiltration from losing river 

reaches, 11.05 ft3

/s,

• discharge from springs south of Laguna 

Tortuguero, 2.37 ft3/s,

• discharge directly to Laguna Tortuguero, 

2.86 ft3

/s, 

• discharge from other springs, 4.96 ft3/s, 

• discharge to wetland areas northeast of 

Laguna Tortuguero, 3.32 ft3/s,

• discharge to gaining river reaches, 8.17 ft3/s,

• discharge to the sea, 0.57 ft3/s,

• discharge to pumping wells, 26.35 ft3/s. 

The total calibrated ground-water flow was 48.60 

ft3/s.

6. Based on the results of the sensitivity analysis, 

transmissivity is the most sensitive parameter and 

riverbed conductance the least sensitive.

7. A transient simulation from 1943 to 2010 shows a 

decrease in ground-water withdrawals of 6 Mgal/d 

(9.3 ft3/s), which produces a rise in aquifer heads 

and increase in ground-water discharge to springs 

and wetland areas.
Model Limitations and Additional Data Needs 51

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Appendix 55

APPENDIXES
56 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico
Appendix 57

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer. Steady-state simulation for 

hydrologic conditions of March 1995.

 BASIC INPUT PACKAGE 

 1 36 73 1 1 

 11 8 3 23 0 0 0 18 17 0 0 0 23 0 0 0 0 0 0 0 0 0 0 0

 0 0 

 5 1 (20I3) 4 

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /* 01

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /* 02

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /* 03

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0

 0 0 0 0 0 0 0 0 0 0 0 0 0

 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 /* 04

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 0 0 1 1 1 0 0 0 0

 1 1 1 1 1 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 /* 05

 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 0

 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 /* 06

 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 3 3 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 /* 07

 1 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 3 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 3 3 1 1 1 1 1 1 1 1 1 1 1 1 /* 08

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 3 3 3 3 3 1 1 1 1 1 1

 1 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 /* 09

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 4 1 1 1 1

 1 1 1 1 1 1 1 3 1 1 1 1 1

 1 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 /* 10

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 4 1 1 1 1

 1 1 1 1 1 1 1 3 1 1 1 1 1

 1 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 /* 11

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 3 3 1 1 1 1 1

 1 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 /* 12

 1 1 1 1 1 1 1 1 1 1 2 2 2 1 1 1 2 2 2 2

 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 3 3 1 1 1 1 4 4

 1 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 /* 13

 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2

 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 3 1 1 4 4 1 1 1

 1 1 1 1 1 1 3 1 1 1 1 1 1 1 1 1 1 1 1 1 /* 14

 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2

 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 3 3 1 1 4 4 4 4 1
58 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 1 1 1 1 4 3 1 3 3 1 1 1 1 1 1 1 1 1 1 1 /* 15

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 2 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 3 3 1 1 1 1 1 1 1 1

 1 1 1 1 4 3 3 1 1 3 1 1 1 1 1 1 1 1 1 1 /* 16

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 4 4 4 1

 1 1 3 3 1 1 1 1 1 1 1 1 1

 1 1 4 4 4 1 1 1 3 1 1 1 4 4 4 1 1 1 1 1 /* 17

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 1 4 4 1 1 1 1 1 1 1 1 1 1 1 1 1 4 4 4 1

 1 3 3 1 1 1 1 1 1 1 1 1 1

 1 1 4 4 4 3 3 3 1 1 1 1 4 4 4 4 1 1 1 4 /* 18

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 5

 5 4 4 1 1 1 1 1 1 4 4 1 4 4 1 4 4 4 4 1

 1 3 1 1 1 1 1 1 1 1 1 1 1

 1 1 1 1 3 3 1 1 1 1 1 1 1 4 4 1 1 4 4 4 /* 19

 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

 5 5 1 1 1 1 1 1 1 1 4 4 4 1 4 4 4 4 4 4

 1 3 3 1 1 1 1 1 1 4 4 4 4

 10 10 10 10 3 3 3 10 10 10 10 10 10 10 10 10 10 10 4 10 /* 20

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 4 4 10 10 10 10 4 4 4

 10 10 10 3 3 10 10 10 10 4 4 10 10

 4 10 10 10 10 3 3 3 3 10 10 10 10 10 10 10 10 10 4 10 /* 21

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 4 4 4 4 4

 4 4 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 4

 10 10 10 10 3 3 4 4 10 4 4 10 10

 10 10 10 10 10 3 10 3 3 10 10 10 10 10 10 10 10 4 10 10 /* 22

 10 10 10 4 10 10 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 10 10 10 10 10 10 10 10 10 10 4 4 10 10 10 10 10 10 10 4

 10 10 3 3 3 3 4 4 4 4 4 10 10

 10 4 4 4 4 3 3 3 3 10 10 10 10 10 10 10 10 10 10 10 /* 23

 10 10 10 4 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 10 10 10 4 4 10 10 10 10 10 4 4 4 4 4 4 4 4 4 4

 3 3 3 4 10 10 3 4 4 4 4 10 10

 4 4 10 10 10 10 10 10 3 3 3 10 10 10 10 10 10 10 10 4 /* 24

 4 4 4 4 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 10 4 4 4 4 10 10 10 10 4 4 4 4 4 4 4 4 4 4 3

 3 10 4 4 10 10 3 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 3 3 10 10 10 10 10 10 10 10 10 /* 25

 4 4 4 4 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 10 10 4 10 10 10 10 4 4 4 4 10 10 10 10 10 10 10 4 3

 10 10 10 10 10 10 3 3 3 3 3 3 10

 10 10 10 10 10 10 10 10 10 3 3 10 10 3 3 3 10 10 10 4 /* 26

 4 4 4 4 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 6 6 4 10 10 10 10 4 4 4 4 10 10 10 10 10 10 10 4 3

 10 10 4 10 10 10 10 10 10 10 10 3 10

 10 10 10 10 10 10 10 10 10 10 3 3 3 3 10 3 10 10 10 10 /* 27

 4 4 4 4 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 6 6 6 6 6 6 6 6 10 10 4 4 4 4 4 4 4 4 4 3

 3 3 4 4 10 10 10 10 10 10 10 3 10

 10 10 10 10 10 10 10 10 10 10 10 3 3 10 10 3 10 3 3 3 /* 28

 3 10 4 4 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 10 10 10 10 10 10 10 10 10 10 4 4 4 4 4 4 4 10 10 10

 10 3 10 10 10 10 10 10 10 10 10 3 3

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 3 3 10 10 /* 29

 3 10 10 10 4 4 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 6 6 6 6 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 3 3 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 3 10 10 /* 30

 3 10 10 10 4 10 9 9 9 9 9 9 9 9 9 9 9 9 9 9

 6 6 6 6 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 59

 3 3 10 10 10 10 10 10 4 4 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 /* 31

 3 10 10 10 4 10 4 10 6 10 6 6 6 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 3

 10 10 10 4 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 3 /* 32

 3 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 3 10

 10 10 10 4 10 10 10 10 10 10 10 10 10

 10 10 10 10 4 4 4 10 10 10 10 10 10 10 10 10 10 10 3 10 /* 33

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 4 4 4 10 10 10 10 10 10 10 10 10 10 3 10 10 /* 34

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 3 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 10 /* 35

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 0 0 0 0 0 10 10 10 10 10 10 10 10 3 3 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 3 10 /* 36

 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10

 10 0 0 0 0 0 10 10 10 10 10 10 10 10 3 10 10 10 10 10

 10 10 10 10 10 10 10 10 10 10 10 10 10

 0 

 5 1.0(10F7.2) -1

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00

 0.56 0.55 0.54 0.57 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.50 0.50 0.50 0.50

 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50

 0.51 0.51 0.51 0.51 0.51 0.50 0.50 0.50 0.50 0.50

 0.50 0.50 0.50 0.50 0.50 0.51 0.51 0.51 0.51 0.51

 0.51 0.52 0.52

 1.19 1.10 0.94 0.60 0.55 0.52 0.49 0.46 0.43 0.41

 0.41 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.50 1.02 1.24 1.33 1.38

 1.36 1.36 1.39 1.37 1.35 1.31 1.27 1.23 1.19 1.15

 1.10 1.05 0.99 0.95 0.90 0.82 0.74 0.67 0.62 0.59

 0.58 0.62 0.68 0.76 0.86 0.97 1.11 1.27 1.44 1.60

 1.74 1.83 1.88

 1.66 1.55 1.37 1.11 0.89 0.66 0.42 0.16 -0.09 -0.27

 -0.29 0.17 0.21 0.24 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.50 1.25 1.73 1.99 2.10 2.14

 2.11 2.09 2.12 2.09 2.03 1.96 1.89 1.82 1.75 1.67

 1.58 1.48 1.37 1.25 1.16 1.06 0.93 0.80 0.70 0.64

 0.62 0.69 0.82 0.97 1.15 1.36 1.62 1.93 2.26 2.57

 2.84 3.03 3.13

 2.04 1.95 1.76 1.49 1.16 0.79 0.37 -0.08 -0.54 -0.95

 -1.26 -1.40 -1.46 -1.22 -0.20 -0.01 0.11 0.00 0.00 0.00

 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.00 0.50 1.55 2.00 2.38 2.59 2.66 2.67

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
60 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 2.66 2.62 2.57 2.51 2.43 2.33 2.24 2.15 2.06 1.97

 1.86 1.74 1.60 1.46 1.33 1.19 1.04 0.85 0.72 0.63

 0.57 0.71 0.91 1.11 1.34 1.62 1.97 2.41 2.90 3.37

 3.76 4.03 4.17

 2.39 2.32 2.13 1.83 1.43 0.93 0.35 -0.28 -0.94 -1.60

 -2.21 -2.74 -3.10 -3.13 -2.79 -2.35 -1.62 -0.26 0.11 0.30

 0.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

 0.00 0.00 0.50 1.75 2.37 2.68 3.07 3.22 3.17 3.06

 2.98 2.90 2.80 2.71 2.60 2.49 2.38 2.29 2.19 2.09

 1.98 1.86 1.72 1.57 1.44 1.28 1.11 0.80 0.69 0.60

 0.60 0.66 0.98 1.21 1.46 1.77 2.18 2.77 3.47 4.12

 4.64 5.01 5.20

 2.77 2.67 2.46 2.14 1.71 1.13 0.39 -0.40 -1.23 -2.11

 -3.06 -3.99 -4.72 -5.10 -5.07 -4.59 -3.66 -2.40 -1.32 -0.43

 0.23 0.61 0.75 0.76 0.50 0.50 0.50 0.50 0.50 0.50

 0.50 0.50 1.81 2.63 3.08 3.53 3.87 3.85 3.60 3.29

 3.11 3.01 2.91 2.81 2.69 2.55 2.44 2.34 2.24 2.12

 2.00 1.88 1.75 1.62 1.50 1.32 1.23 1.13 1.03 0.80

 0.87 0.86 1.15 1.31 1.51 1.80 2.20 3.01 4.03 4.92

 5.61 6.08 6.31

 3.17 3.05 2.81 2.44 1.95 1.32 0.55 -0.34 -1.38 -2.52

 -3.78 -5.05 -6.17 -6.99 -7.25 -6.73 -5.55 -3.93 -2.27 -0.81

 0.33 1.14 1.67 1.97 1.99 2.05 2.14 2.25 2.37 2.46

 2.56 2.76 3.27 3.71 4.00 4.39 4.54 4.36 3.91 3.32

 3.14 3.09 3.01 2.91 2.79 2.58 2.48 2.41 2.32 2.12

 2.01 1.89 1.75 1.63 1.54 1.55 1.55 1.51 1.39 1.09

 1.13 1.52 1.39 1.36 1.46 1.71 1.97 3.14 4.60 5.78

 6.61 7.17 7.45

 3.60 3.47 3.20 2.81 2.27 1.59 0.76 -0.22 -1.40 -2.74

 -4.27 -5.91 -7.52 -8.84 -9.38 -8.74 -7.21 -5.00 -2.74 -0.81

 0.67 1.73 2.48 3.02 3.20 3.33 3.50 3.73 3.97 4.12

 4.22 4.34 4.55 4.79 4.94 5.17 5.16 4.92 4.37 3.09

 3.05 3.17 3.12 3.02 2.99 2.52 2.51 2.50 2.48 2.03

 2.00 1.91 1.74 1.60 1.51 1.69 1.79 1.82 1.76 1.62

 1.79 2.39 2.70 2.89 3.07 3.21 3.23 3.11 5.22 6.65

 7.59 8.21 8.54

 4.08 3.94 3.66 3.24 2.68 1.96 1.08 0.03 -1.25 -2.77

 -4.57 -6.66 -8.92 -10.93 -12.07 -11.08 -9.07 -5.85 -2.80 -0.39

 1.31 2.46 3.29 3.88 4.14 4.33 4.58 4.92 5.38 5.51

 5.55 5.56 5.58 5.63 5.63 5.65 5.56 5.39 5.11 4.72

 4.26 3.31 3.20 3.04 3.02 3.01 2.89 2.71 2.49 2.26

 2.01 1.98 1.70 1.51 1.53 1.89 2.04 2.07 2.07 2.13

 2.63 3.22 3.68 4.06 4.30 4.37 4.22 3.93 6.22 7.70

 8.66 9.23 9.62

 4.63 4.48 4.19 3.76 3.18 2.43 1.52 0.43 -0.91 -2.53

 -4.56 -7.17 -10.14 -13.16 -15.71 -13.59 -11.37 -6.35 -2.32 0.48

 2.23 3.24 3.98 4.55 4.85 5.11 5.40 5.79 6.20 6.21

 6.18 6.12 6.05 5.97 5.89 5.79 5.68 5.52 5.33 5.08

 4.79 4.46 4.19 3.93 3.45 3.53 3.29 2.95 2.52 2.47

 2.02 1.89 1.55 1.56 2.04 2.28 2.32 2.29 2.26 2.49

 3.23 3.94 4.53 5.01 5.28 5.27 4.98 5.40 7.72 9.06

 9.86 10.14 10.76

 5.24 5.10 4.80 4.36 3.76 3.01 2.09 0.99 -0.32 -1.94

 -3.99 -6.70 -10.45 -14.86 -21.58 -15.15 -14.98 -5.88 -1.14 1.66

 3.07 3.76 4.42 5.03 5.41 5.74 5.99 6.21 6.32 6.31

 6.26 6.19 6.11 6.03 5.94 5.84 5.73 5.59 5.43 5.22

 4.99 4.74 4.47 4.17 3.75 4.00 3.73 3.23 2.70 2.49

 2.02 2.01 2.25 2.49 2.70 2.74 2.57 2.47 2.19 2.83

 3.76 4.60 5.28 5.81 6.10 6.00 6.54 8.12 9.51 10.47

 11.04 11.44 11.96

 5.94 5.79 5.48 5.03 4.43 3.68 2.78 1.72 0.49 -1.00

 -2.87 -5.28 -8.55 -12.15 -17.04 -10.92 -7.08 -2.80 0.54 2.48

 3.40 3.99 4.70 5.40 5.92 6.28 6.46 6.50 6.46 6.42

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 61

 6.35 6.26 6.17 6.08 5.99 5.90 5.81 5.69 5.54 5.37

 5.19 4.99 4.79 4.57 4.38 4.38 4.14 3.52 2.57 2.49

 2.04 2.08 2.88 3.28 3.43 3.27 2.71 2.72 2.99 2.97

 4.16 5.11 5.87 6.46 6.88 7.23 8.49 9.71 10.71 11.44

 11.94 12.45 12.59

 6.71 6.55 6.24 5.79 5.18 4.43 3.55 2.59 1.49 0.20

 -1.34 -3.19 -5.38 -7.00 -8.11 -5.82 -3.21 -0.66 1.45 2.88

 3.73 4.46 5.25 5.95 6.49 6.82 6.90 6.79 6.63 6.56

 6.46 6.34 6.23 6.12 6.04 5.97 5.91 5.81 5.68 5.54

 5.39 5.23 5.09 4.95 4.85 4.79 4.58 3.97 2.79 2.64

 2.26 2.68 3.65 4.08 4.19 3.99 3.36 3.71 3.77 3.47

 4.55 5.52 6.34 6.97 7.38 8.17 9.51 10.61 11.46 12.07

 12.59 13.05 13.24

 7.57 7.40 7.08 6.62 6.01 5.23 4.43 3.53 2.58 1.53

 0.36 -0.95 -2.31 -3.19 -3.26 -2.22 -0.81 0.76 2.24 3.40

 4.31 5.08 5.85 6.54 7.07 7.36 7.41 7.20 6.83 6.73

 6.60 6.41 6.27 6.15 6.07 6.05 6.03 5.95 5.85 5.72

 5.59 5.46 5.35 5.25 5.19 5.16 5.11 4.86 4.44 4.29

 4.19 4.35 4.70 4.94 5.02 4.86 4.33 4.70 4.65 4.15

 4.98 6.08 6.97 7.60 8.32 9.46 10.54 11.46 12.21 12.80

 13.36 13.76 13.94

 8.48 8.28 7.96 7.50 6.89 6.10 5.29 4.49 3.66 2.83

 2.01 1.08 0.12 -0.60 -0.57 -0.08 0.77 1.93 3.10 4.17

 4.97 5.66 6.44 7.12 7.64 7.98 8.12 7.98 7.64 7.48

 7.34 7.16 6.98 6.80 6.56 6.30 6.22 6.13 6.02 5.90

 5.78 5.68 5.59 5.52 5.49 5.51 5.81 5.92 5.83 5.75

 5.69 5.69 5.75 5.88 6.01 6.03 5.92 5.94 5.82 5.51

 5.25 6.73 7.72 8.60 9.60 10.56 11.45 12.24 12.90 13.43

 13.90 14.23 14.40

 9.47 9.17 8.84 8.41 7.81 6.99 6.14 5.34 4.60 3.97

 3.42 2.82 2.15 1.52 1.52 1.88 2.64 3.63 4.63 5.61

 6.64 7.34 7.98 8.52 8.96 9.23 9.32 9.20 8.95 8.73

 8.54 8.35 8.12 7.87 7.56 7.12 6.91 6.76 6.62 6.50

 6.40 6.33 6.29 6.29 6.34 6.48 6.89 7.10 7.15 7.13

 7.05 6.90 6.69 6.75 7.07 7.25 7.29 7.27 7.12 6.75

 6.06 7.73 8.74 9.75 10.65 11.48 12.24 12.93 13.52 13.99

 14.39 14.69 14.83

 10.17 9.98 9.72 9.37 8.83 7.81 6.84 6.02 5.39 4.91

 4.61 4.33 4.04 3.69 3.78 4.38 5.19 6.11 7.06 8.06

 9.04 9.55 9.97 10.33 10.58 10.69 10.66 10.51 10.25 9.94

 9.65 9.39 9.12 8.82 8.51 8.19 7.93 7.72 7.55 7.41

 7.33 7.30 7.34 7.43 7.58 7.79 8.09 8.31 8.42 8.44

 8.35 8.06 7.27 7.31 8.16 8.48 8.60 8.60 8.49 8.18

 7.44 9.06 10.04 10.89 11.66 12.37 13.02 13.62 14.13 14.56

 14.91 15.17 15.30

 10.38 10.34 10.18 9.93 9.61 8.59 7.42 6.55 5.95 5.58

 5.41 5.35 5.35 5.44 5.85 6.65 7.50 8.40 9.29 10.12

 10.69 11.20 11.49 11.75 11.88 11.90 11.81 11.64 11.38 11.05

 10.67 10.31 9.99 9.66 9.35 9.04 8.76 8.51 8.30 8.15

 8.07 8.09 8.20 8.37 8.59 8.86 9.18 9.44 9.58 9.65

 9.63 9.51 9.29 9.31 9.57 9.72 9.81 9.85 9.83 9.80

 9.85 10.55 11.25 11.93 12.57 13.17 13.73 14.25 14.71 15.09

 15.41 15.64 15.75

 10.59 10.52 10.37 10.14 9.76 8.86 7.68 6.76 6.23 6.04

 5.95 6.02 6.22 6.59 7.27 8.07 8.98 9.91 10.81 11.59

 12.17 12.60 12.86 13.03 13.10 13.06 12.95 12.77 12.49 12.15

 11.71 11.25 10.81 10.46 10.13 9.84 9.52 9.22 8.97 8.77

 8.67 8.73 8.96 9.21 9.50 9.83 10.14 10.38 10.54 10.63

 10.65 10.62 10.57 10.58 10.66 10.71 10.77 10.85 10.93 11.06

 11.28 11.72 12.25 12.80 13.35 13.88 14.39 14.85 15.25 15.60

 15.88 16.08 16.17

 10.82 10.75 10.61 10.43 9.86 8.78 7.65 6.49 6.10 6.29

 6.42 6.64 6.98 7.48 8.18 9.00 10.00 11.03 12.00 12.83

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
62 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 13.48 13.88 14.15 14.24 14.24 14.18 14.06 13.89 13.64 13.31

 12.82 12.30 11.78 11.36 11.05 10.82 10.66 10.48 10.30 10.14

 10.06 9.94 9.86 10.02 10.41 10.71 10.95 11.13 11.27 11.36

 11.38 11.38 11.37 11.38 11.42 11.48 11.55 11.67 11.83 12.01

 12.27 12.63 13.08 13.56 14.05 14.54 15.00 15.41 15.78 16.09

 16.34 16.51 16.60

 11.06 10.99 10.86 10.68 10.03 8.76 7.64 6.52 6.20 6.48

 6.73 7.06 7.49 8.06 8.79 9.80 10.94 12.04 13.04 13.92

 14.62 15.02 15.23 15.29 15.25 15.19 15.10 14.99 14.80 14.58

 14.33 13.92 13.16 12.74 12.48 12.33 12.33 12.37 12.42 12.45

 12.34 11.98 11.54 11.40 11.50 11.63 11.75 11.86 11.96 12.04

 12.05 12.04 12.03 12.04 12.07 12.15 12.28 12.42 12.61 12.84

 13.12 13.46 13.87 14.30 14.74 15.18 15.59 15.97 16.32 16.61

 16.84 16.99 17.07

 11.28 11.22 11.08 10.89 10.28 8.60 7.56 6.77 6.42 6.61

 6.87 7.27 7.76 8.35 9.17 10.30 11.55 12.75 13.87 14.86

 15.59 16.03 16.22 16.28 16.26 16.22 16.15 16.11 16.07 16.03

 16.09 16.07 15.66 15.49 15.45 15.43 15.43 15.40 15.42 15.35

 15.08 14.59 13.84 13.18 12.63 12.64 12.68 12.72 12.73 12.71

 12.69 12.66 12.63 12.63 12.65 12.74 12.90 13.09 13.33 13.60

 13.90 14.24 14.61 15.00 15.40 15.80 16.21 16.58 16.92 17.20

 17.42 17.56 17.63

 11.50 11.43 11.27 11.03 10.72 9.81 8.80 7.71 6.80 6.61

 6.78 7.34 7.79 8.27 9.00 10.15 11.73 13.29 14.67 15.78

 16.55 17.01 17.26 17.38 17.39 17.32 17.27 17.28 17.36 17.47

 17.64 17.81 18.43 19.00 19.36 19.54 19.59 19.51 19.32 18.79

 18.35 17.62 16.52 15.33 14.17 13.65 13.68 13.64 13.56 13.43

 13.34 13.28 13.24 13.24 13.28 13.39 13.57 13.80 14.08 14.44

 14.73 15.06 15.40 15.75 16.11 16.48 16.87 17.24 17.58 17.88

 18.08 18.21 18.26

 11.73 11.64 11.45 11.16 10.74 10.15 9.51 8.36 7.22 6.85

 6.92 7.43 7.70 7.86 8.34 9.39 11.61 13.73 15.46 16.72

 17.57 18.07 18.37 18.51 18.56 18.53 18.55 18.62 18.76 19.04

 19.41 19.90 21.26 22.35 23.07 23.40 23.50 23.65 23.45 22.69

 21.82 20.71 19.41 17.84 16.32 15.19 14.74 14.58 14.42 14.25

 14.10 13.98 13.90 13.89 13.94 14.06 14.27 14.56 14.94 15.44

 15.75 16.05 16.35 16.66 16.98 17.31 17.67 18.02 18.37 18.76

 18.93 19.09 19.06

 11.98 11.88 11.67 11.34 10.86 10.22 9.38 8.19 6.94 7.16

 7.24 7.62 7.59 7.06 7.12 7.33 11.26 14.25 16.42 17.93

 18.96 19.39 19.57 19.66 19.73 19.80 19.92 20.10 20.36 20.83

 21.49 22.43 23.82 25.14 26.16 26.96 27.59 27.91 27.76 27.11

 25.75 24.20 22.59 20.79 18.83 17.16 15.99 15.65 15.36 15.14

 14.97 14.87 14.80 14.82 14.88 15.02 15.27 15.60 16.11 16.76

 17.11 17.42 17.62 17.85 18.10 18.37 18.68 19.00 19.33 19.65

 19.93 20.27 20.14

 12.26 12.15 11.93 11.58 11.08 10.42 9.51 8.14 7.51 8.07

 8.04 8.08 7.94 7.76 7.67 7.43 11.54 15.38 17.90 19.75

 20.98 20.93 20.81 20.76 20.78 20.91 21.12 21.46 21.94 22.49

 23.39 24.73 26.84 28.74 30.12 31.31 32.19 32.37 32.18 31.48

 29.91 28.07 25.98 23.82 21.56 19.47 17.86 17.02 16.61 16.31

 16.10 16.00 15.99 16.06 16.17 16.42 16.83 17.28 18.00 18.94

 19.52 19.85 19.72 19.77 19.91 20.11 20.36 20.62 20.90 21.19

 21.50 21.97 21.83

 12.59 12.48 12.24 11.89 11.40 10.78 10.04 9.25 8.83 8.92

 9.15 9.11 8.90 8.91 8.50 7.65 11.76 17.57 20.10 22.41

 24.68 22.86 22.15 21.86 21.76 21.94 22.31 22.93 23.79 25.34

 26.94 28.85 31.39 33.40 34.95 36.13 36.92 37.31 37.12 36.39

 34.54 32.47 30.04 27.44 24.48 21.76 20.01 18.79 18.31 17.93

 17.62 17.39 17.38 17.46 17.62 18.12 18.83 19.96 21.12 22.22

 23.13 23.81 23.31 23.12 23.10 23.18 23.32 23.50 23.69 23.90

 24.14 24.61 24.85

 13.07 12.95 12.71 12.35 11.87 11.29 10.66 10.08 9.74 9.72

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 63

 9.82 9.89 10.03 9.90 9.47 8.13 9.19 15.49 19.79 23.01

 25.90 24.68 24.05 24.12 25.04 25.86 26.70 27.72 29.22 31.38

 33.28 35.30 37.60 39.65 41.29 42.50 43.26 43.67 43.27 42.23

 40.19 37.76 34.95 31.81 28.55 25.40 23.02 21.21 20.41 19.95

 19.55 19.38 19.36 19.55 20.14 21.13 22.21 23.89 25.45 26.95

 28.39 28.73 27.85 27.45 27.25 27.21 27.23 27.28 27.35 27.40

 27.42 27.45 27.50

 13.97 13.86 13.62 13.27 12.78 12.24 11.68 11.22 10.99 11.11

 11.33 11.48 11.51 11.41 11.17 10.90 10.61 13.86 20.40 24.05

 26.93 26.71 27.37 28.80 30.73 32.22 33.59 35.02 36.70 38.62

 40.58 42.88 45.39 47.67 49.50 50.75 51.36 51.32 50.48 48.86

 46.49 43.56 40.19 36.55 32.79 29.46 26.89 24.84 23.62 22.90

 22.07 21.83 21.81 22.14 23.30 24.77 26.35 28.32 30.32 32.47

 33.47 33.45 32.51 32.14 31.81 31.67 31.59 31.51 31.43 31.32

 31.12 30.86 30.72

 15.64 15.63 15.63 15.47 15.20 14.68 14.03 13.34 12.92 13.02

 13.56 13.64 13.61 13.64 13.74 14.22 16.04 19.64 23.81 25.79

 27.50 29.43 31.74 33.99 36.15 38.06 39.84 41.62 43.40 45.38

 47.37 50.31 53.39 56.18 58.36 59.72 60.18 59.77 58.41 56.04

 53.09 49.46 45.49 41.49 37.41 33.54 30.69 28.81 27.60 26.88

 26.51 25.91 25.62 25.89 27.05 28.68 31.09 33.66 36.14 37.27

 37.61 37.83 37.69 37.87 38.17 38.11 37.89 37.64 37.36 37.00

 36.43 35.93 35.70

 29.11 29.06 28.97 28.58 27.92 26.53 24.90 22.93 20.65 18.42

 16.45 16.22 16.48 16.88 17.67 19.09 21.44 24.56 28.86 28.50

 28.04 32.16 35.45 38.28 40.82 43.06 45.13 47.24 49.31 51.70

 54.57 58.74 62.94 66.83 69.76 71.37 71.59 70.79 68.77 64.83

 61.02 56.59 51.44 46.60 42.20 38.10 35.61 34.98 34.80 34.13

 33.34 31.65 30.59 30.39 31.11 32.94 35.98 39.25 40.78 43.39

 45.19 46.49 46.84 46.35 47.40 47.13 46.55 45.97 45.42 44.86

 44.22 43.47 43.16

 55.34 55.02 54.31 53.04 51.07 48.18 44.21 39.77 33.89 28.03

 24.26 23.17 23.08 23.34 24.09 25.21 26.42 27.79 29.50 29.80

 31.38 35.39 39.04 42.22 44.94 47.36 49.58 52.08 55.12 58.57

 64.77 71.54 78.29 85.17 90.06 92.21 91.47 90.24 88.05 91.92

 88.78 84.83 80.10 74.18 64.93 54.17 47.04 46.15 46.92 44.47

 41.32 36.80 34.63 33.84 34.28 36.18 40.19 42.82 47.47 53.87

 65.02 70.14 72.11 69.02 63.27 61.06 59.43 58.18 57.21 56.39

 55.66 55.04 54.72

 85.32 84.65 83.19 80.73 76.99 71.95 65.46 58.35 48.65 37.66

 34.56 32.47 31.39 30.82 30.73 30.80 30.61 30.00 30.25 30.70

 33.54 38.66 42.96 46.60 49.59 52.43 55.90 59.61 63.86 69.01

 76.71 84.95 94.97 110.84 119.48 122.62 117.72 116.37 126.30 158.95

 204.75 236.09 243.62 244.19 250.34 157.82 162.49 135.16 115.61 96.76

 80.57 81.14 75.61 66.28 53.64 45.82 44.24 73.59 79.81 88.61

 100.32 103.41 102.93 98.45 89.37 83.82 80.25 77.82 76.10 74.84

 73.90 73.24 72.90

 108.28 107.30 105.16 101.53 95.71 88.24 80.17 71.85 62.32 50.28

 42.56 39.54 37.69 36.62 35.85 35.00 33.54 31.39 30.52 31.23

 35.07 41.70 46.88 50.82 54.34 57.83 61.92 66.27 70.99 76.85

 84.44 93.94 105.04 117.85 127.18 133.95 138.77 142.94 154.30 177.13

 224.80 0.00 0.00 0.00 0.00 0.00 259.18 241.20 193.18 159.25

 142.59 137.79 123.06 96.49 50.01 49.30 91.67 117.84 126.79 133.35

 135.78 132.72 123.81 118.51 111.65 105.11 99.69 96.07 93.59 91.86

 90.67 89.91 89.54

 118.54 117.40 114.94 110.85 104.66 96.01 86.01 76.04 67.61 58.16

 49.38 44.74 42.14 40.65 39.44 37.96 35.48 32.18 31.01 31.51

 36.55 44.08 49.08 53.11 56.81 60.20 65.14 70.27 78.99 87.55

 96.18 106.12 117.31 126.73 135.73 147.01 166.56 162.18 166.96 185.45

 234.44 0.00 0.00 0.00 0.00 0.00 298.83 290.22 242.30 198.40

 183.45 167.87 145.85 110.11 51.48 85.35 118.78 142.81 155.30 159.80

 155.63 149.88 138.47 128.44 121.94 115.60 109.60 105.44 102.58 100.61

 99.28 98.45 98.05

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
64 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 1 1 1 

BLOCK CENTER FLOW INPUT PACKAGE:

 1 -6 1.00E+30 0 5.00E-01 1 0 

 0

 0 1.

 0 1000.

 0 1000.

 11 1.157e-05(12F7.0) -11

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 01

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 200. 200. 200. 200. 0. 0. 0. 0. 0. 0. 0. 0. /* 02

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 300.

 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 400.

 500. 500. 500. 500. 500. 500. 500. 500. 500. 500. 500. 500.

 500.

 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 0. /* 03

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 300. 

 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 300. 300.

 300. 300. 300. 300. 300. 500. 500. 300. 300. 300. 400. 500.

 600. 600. 600. 600. 600. 600. 600. 600. 600. 600. 600. 600.

 600.

 500. 400. 400. 400. 400. 400. 400. 400. 400. 400. 900. 900. /* 04

 900. 900. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 400.

 400. 400. 400. 500. 400. 400. 500. 500. 500. 500. 500. 500.

 500. 500. 500. 500. 500. 500. 500. 500. 500. 400. 500. 600.

 700. 700. 700. 700. 700. 700. 700. 700. 700. 700. 700. 700.

 700.

 750. 500. 500. 500. 500. 500. 500. 500. 500. 500. 1000. 1000. /* 05

 1000. 1000. 1000. 1000. 1000. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 750. 750.

 750. 750. 750. 750. 500. 500. 1000. 1000. 1000. 1000. 1000. 1000.

 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 800. 800. 800.

 800. 800. 800. 800. 800. 800. 800. 800. 800. 800. 800. 800.

 800.

 800. 750. 750. 600. 600. 600. 600. 600. 600. 600. 1100. 1100. /* 06

 1100. 1100. 1100. 1100. 1100. 1100. 800. 600. 600. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 5000. 5000. 600.

 600. 600. 600. 1000. 2000. 2500. 3000. 3000. 3500. 3600. 4000. 4800.

 6000. 6000. 4000. 4000. 2200. 2200. 2000. 1800. 1500. 1200. 1000. 900.

 900. 900. 900. 900. 900. 900. 900. 900. 900. 900. 900. 900.

 900.

 1000. 1000. 1000. 1000. 1000. 750. 750. 1000. 1000. 1000. 1200. 1200. /* 07

 1200. 1200. 1200. 1200. 1200. 1200. 900. 700. 700. 700. 1000. 2000.

 3000. 4000. 5000. 5000. 5000. 5000. 5000. 5000. 6000. 6000. 6000. 1000.

 1000. 1500. 2000. 3200. 3200. 4000. 3600. 4000. 4000. 4400. 5000. 6000.

 7200. 7200. 6000. 5800. 4000. 4000. 3400. 2200. 2000. 1800. 1500. 1500.

 1200. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000.

 1000.

 1250. 1250. 1250. 1250. 1250. 1250. 1250. 1250. 1250. 1250. 1500. 1500. /* 08

 1500. 1500. 1500. 1500. 1500. 1500. 1000. 1000. 1000. 1000. 1000. 1000.

 2000. 3000. 4000. 6000. 6000. 6000. 6000. 6000. 7000. 7000. 6000. 5000.

 4000. 2500. 3000. 4400. 4400. 5000. 4400. 4600. 4600. 5200. 6000. 7500.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 65

 8400. 8400. 7500. 6200. 6000. 5800. 4800. 4000. 3400. 2200. 2000. 2000.

 1800. 1500. 1500. 1250. 1250. 1250. 1250. 1250. 1250. 1250. 1250. 1250.

 1250.

 1500. 1500. 1500. 1500. 1500. 1500. 1500. 1500. 1500. 1500. 2000. 2000. /* 09

 2000. 2000. 2000. 2000. 2000. 2000. 1500. 1500. 1500. 1500. 1500. 1500.

 2000. 3000. 5000. 5000. 7000. 7000. 7000. 7000. 8000. 8000. 8000. 9000.

 7000. 6000. 4500. 5600. 5600. 6000. 5200. 5300. 5300. 6500. 7800. 9000.

 9600. 9600. 9000. 7900. 7800. 7000. 6500. 5100. 4800. 4000. 3400. 3400.

 2600. 2450. 2450. 1700. 1700. 1500. 1500. 1300. 1300. 1300. 1100. 1100.

 1100.

 1750. 1750. 1750. 1750. 1750. 1750. 1750. 1750. 1750. 1750. 2000. 2500. /* 10

 2750. 3000. 3000. 3000. 3000. 3000. 2500. 1750. 1750. 1750. 1750. 2500.

 9000. 9000. 9000. 9000. 9000. 9000. 9000. 9000. 10000. 15000. 15000. 20000.

 25000. 25000. 25000. 30000. 30000. 30000. 30000. 6000. 6000. 7800. 9600. 10500.

 10800. 10800. 10500. 9600. 9600. 8200. 8200. 6200. 6000. 5800. 4800. 4800.

 3400. 3400. 3400. 3000. 3000. 3000. 2000. 1800. 1800. 1800. 1500. 1500.

 1500.

 2000. 2000. 2000. 2000. 2000. 2000. 2000. 2000. 2000. 2000. 2000. 2000. /* 11

 3000. 3000. 7500. 10000. 10000. 10000. 5000. 5000. 5000. 5000. 5000. 5000.

 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000.

 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 9600. 11400. 12000.

 12000. 12000. 12000. 11400. 11400. 10400. 10400. 9000. 9000. 6000. 6000. 5800.

 4800. 4800. 4800. 4500. 4000. 4000. 3400. 2200. 2200. 2200. 2000. 2000.

 2000.

 2250. 2250. 2250. 2250. 2250. 2250. 2250. 2250. 2250. 2250. 2250. 2250. /* 12

 2250. 8000. 9000. 10000. 12500. 14000. 14000. 18000. 18000. 15000. 10000. 10000.

 10000. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500.

 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 13200. 13400.

 13400. 13400. 13400. 13000. 13000. 12600. 12600. 12000. 12000. 10000. 10000. 6200.

 6000. 6000. 6000. 5800. 5800. 5800. 5000. 5000. 5000. 5000. 5000. 5000.

 5000.

 2500. 2500. 2500. 2500. 2500. 2500. 2500. 2500. 2500. 2500. 2500. 2500. /* 13

 2500. 8000. 10000. 12500. 14000. 14000. 18000. 30000. 60000. 40000. 20000. 15000.

 12500. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000.

 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 14800. 14800.

 14800. 14800. 14800. 14800. 14800. 14800. 14800. 14800. 14800. 14800. 14800. 14800.

 14800. 14800. 14800. 13000. 12000. 10000. 10000. 10000. 10000. 10000. 10000. 10000.

 10000.

 2750. 2750. 2750. 2750. 2750. 2750. 2750. 2750. 2750. 2750. 2750. 2750. /* 14

 8750. 10000. 14000. 14000. 14000. 14000. 18000. 30000. 40000. 25000. 20000. 20000.

 15000. 20000. 25000. 25000. 22500. 22500. 25000. 25000. 25000. 25000. 25000. 25000.

 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000.

 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 22000. 22000. 22000. 22000.

 22000. 22000. 20000. 20000. 20000. 20000. 17500. 17000. 17000. 17000. 14000. 12500.

 12500.

 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. /* 15

 8800. 15000. 15000. 15000. 15000. 20000. 25000. 35000. 40000. 40000. 30000. 30000.

 30000. 30000. 30000. 30000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000.

 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000.

 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000. 28000.

 20000. 20000. 20000. 20000. 20000. 20000. 20000. 20000. 20000. 20000. 15000. 15000.

 15000.

 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. /* 16

 8500. 12500. 12500. 13000. 13000. 12500. 15000. 15000. 40000. 40000. 35000. 35000.

 35000. 35000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000.

 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000. 30000.

 30000. 30000. 30000. 30000. 30000. 30000. 30000. 28000. 25000. 22500. 22500. 22500.

 22500. 22500. 22500. 22500. 22500. 22500. 22500. 22500. 22500. 22500. 25000. 25000.

 25000.

 4000. 4000. 4000. 4000. 4000. 4000. 4000. 4000. 4000. 4000. 4000. 4000. /* 17

 8500. 10000. 10000. 10000. 9000. 7500. 7500. 7500. 5000. 7500. 10000. 11000.

 12500. 15000. 20000. 20000. 25000. 30000. 35000. 35000. 35000. 35000. 35000. 35000.

 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 30000. 30000.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
66 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 30000. 30000. 30000. 30000. 30000. 30000. 30000. 27500. 25000. 25000. 25000. 25000.

 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000. 25000.

 25000.

 25000. 4500. 4500. 4500. 4500. 4500. 4500. 4500. 4500. 4500. 4500. 4500. /* 18

 5000. 10000. 10000. 8000. 8000. 8500. 8500. 8000. 10000. 10000. 13400. 15000.

 20000. 25000. 30000. 30000. 30000. 30000. 35000. 40000. 40000. 40000. 40000. 40000.

 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 35000. 35000.

 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000.

 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 35000. 30000. 30000.

 30000.

 30996. 30840. 30950. 30988. 31250. 5000. 5000. 5000. 5000. 5000. 6000. 5000. /* 19

 5000. 10000. 10000. 9000. 9000. 9000. 9000. 9000. 10000. 12500. 15000. 17500.

 20000. 25000. 30000. 30000. 35000. 35000. 40000. 45000. 45000. 45000. 45000. 45000.

 45000. 45000. 45000. 45000. 45000. 45000. 45000. 45000. 45000. 45000. 40000. 40000.

 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000. 40000.

 40000. 35000. 25000. 25000. 30000. 35000. 40000. 40000. 40000. 40000. 35000. 35000.

 35000.

 32246. 31990. 32082. 32162. 32382. 5200. 5200. 5200. 5200. 5200. 6000. 6000. /* 20

 6500. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 15000. 15000. 20000.

 25000. 30000. 33750. 33750. 33750. 33750. 33750. 35000. 42000. 42000. 42000. 42000.

 42000. 42000. 42000. 42000. 42000. 42000. 42000. 42000. 42000. 45000. 45000. 45000.

 45000. 50000. 60000. 60000. 70000. 35000. 40000. 35000. 35000. 35000. 35000. 35000.

 40000. 35000. 25000. 25000. 30000. 35000. 45000. 45000. 45000. 45000. 45000. 45000.

 45000.

 33750. 33516. 33462. 33440. 5500. 5500. 5500. 5500. 5500. 5500. 5500. 5500. /* 21

 6000. 6500. 12500. 12500. 12500. 12500. 12500. 12500. 12500. 15000. 17500. 20000.

 25000. 30000. 35000. 35000. 35000. 35000. 35000. 35000. 30000. 30000. 30000. 30000.

 20000. 15000. 12500. 10000. 8000. 10000. 20000. 25000. 30000. 40000. 50000. 60000.

 65000. 70000. 70000. 70000. 70000. 70000. 60000. 50000. 45000. 40000. 40000. 35000.

 30000. 25000. 20000. 20000. 20000. 20000. 40000. 50000. 50000. 50000. 50000. 50000.

 50000.

 41012. 35060. 34928. 34882. 6000. 6000. 6000. 6000. 6000. 6000. 6000. 6000. /* 22

 6000. 6500. 6500. 7500. 10000. 12500. 15000. 15000. 17500. 20000. 25000. 30000.

 35000. 40000. 41000. 39000. 36000. 35000. 20000. 15000. 15000. 15000. 15000. 15000.

 15000. 12500. 10000. 7500. 7500. 8000. 9000. 10000. 30000. 35000. 40000. 45000.

 50000. 55000. 60000. 60000. 60000. 60000. 50000. 40000. 39000. 38000. 36000. 35000.

 25000. 25000. 20000. 15000. 15000. 15000. 25000. 35000. 45000. 45000. 45000. 45000.

 45000.

 41474. 39588. 36704. 36582. 6200. 6200. 6200. 6200. 6200. 6200. 6200. 6200. /* 23

 6200. 7500. 7500. 10000. 15000. 17500. 18000. 20000. 22500. 23000. 24000. 25000.

 25000. 30000. 35000. 35000. 30000. 25000. 22500. 20000. 6000. 6000. 6000. 6000.

 6000. 6000. 6000. 6000. 6000. 6000. 8000. 10000. 15000. 25000. 30000. 40000.

 45000. 50000. 50000. 50000. 45000. 40000. 38000. 36000. 34000. 32000. 30000. 29000.

 25000. 25000. 25000. 25000. 20000. 20000. 20000. 20000. 20000. 20000. 20000. 20000.

 20000.

 41828. 40752. 38346. 38134. 37938. 6500. 6500. 6500. 6500. 6500. 6500. 6500. /* 24

 6500. 7500. 9000. 10000. 12500. 15000. 17500. 20000. 25000. 30000. 25000. 25000.

 25000. 32000. 32000. 32000. 32000. 28000. 26000. 25000. 6000. 6000. 6000. 6000.

 6000. 5000. 5000. 5000. 5000. 6000. 6000. 7500. 10000. 15000. 25000. 35000.

 40000. 45000. 45000. 45000. 45000. 42000. 40000. 38000. 36000. 35000. 30000. 29000.

 27000. 25000. 22500. 20000. 15000. 15000. 15000. 15000. 15000. 15000. 15000. 15000.

 15000.

 40662. 40938. 39814. 39512. 39222. 38920. 38750. 7000. 7000. 7000. 7000. 7000. /* 25

 9000. 11000. 12500. 13000. 15000. 17000. 20000. 25216. 24770. 24292. 24362. 23750.

 23000. 22000. 22000. 22000. 22000. 18000. 16000. 12500. 6000. 6000. 6000. 6000.

 6000. 5000. 5000. 3500. 5000. 6000. 6000. 7000. 7500. 10000. 20000. 30000.

 35000. 40000. 45000. 45000. 45000. 42000. 40000. 40000. 38000. 32000. 30000. 25000.

 25000. 20000. 15000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000. 10000.

 10000.

 42234. 41674. 41272. 40860. 40462. 40050. 39746. 39448. 39148. 7000. 7000. 7000. /* 26

 7000. 10000. 12500. 13000. 14000. 15000. 17000. 20000. 22000. 23000. 24000. 24000.

 24200. 22000. 22000. 20000. 18000. 17000. 15000. 10000. 10000. 9000. 9000. 6500.

 4500. 4500. 4500. 3000. 4000. 4500. 5000. 5000. 5000. 7500. 10000. 25000.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 67

 30000. 35000. 40000. 42000. 35000. 30000. 27000. 25000. 15000. 15000. 15000. 15000.

 15000. 15000. 15000. 15000. 10000. 9000. 9000. 9000. 9000. 9000. 9000. 9000.

 9000.

 42956. 42398. 41926. 41432. 40946. 40446. 40028. 39622. 39226. 38778. 7000. 7000. /* 27

 7000. 9000. 12000. 12000. 12000. 14000. 15000. 15876. 20000. 22000. 23000. 24000.

 24000. 22000. 22000. 20000. 15000. 15000. 15000. 10000. 4000. 4000. 4000. 4000.

 4000. 4000. 4000. 3000. 4000. 4000. 4500. 5000. 5000. 8000. 10000. 25000.

 25000. 25000. 25000. 25000. 20000. 20000. 15000. 12500. 10000. 10000. 10000. 10000.

 7500. 7500. 7500. 7500. 7500. 7500. 7500. 7500. 7500. 7500. 7500. 7500.

 7500.

 42320. 41702. 41110. 40482. 39866. 39240. 38656. 38088. 37524. 36918. 36294. 35654. /* 28

 7500. 7500. 7500. 10000. 11000. 12000. 13000. 13000. 15000. 15000. 16000. 18000.

 19000. 18000. 15000. 12500. 10000. 4000. 4000. 4000. 4000. 4000. 4000. 4000.

 4000. 3000. 3000. 2500. 3000. 3000. 3000. 3000. 4000. 9000. 11000. 15000.

 15000. 15000. 15000. 15000. 15000. 15000. 15000. 10000. 10000. 5000. 5000. 5000.

 5000. 5000. 5000. 5000. 5000. 5000. 5000. 5000. 5000. 5000. 5000. 5000.

 5000.

 27000. 27000. 27000. 27000. 27000. 27000. 27000. 26800. 26400. 26000. 26000. 26000. /* 29

 26000. 25600. 23600. 10000. 7000. 7000. 7000. 7000. 7000. 7000. 6000. 5000.

 2200. 2200. 2200. 2300. 2300. 2300. 2300. 2200. 2200. 2200. 2200. 2200.

 2200. 2200. 2200. 2200. 2200. 2200. 2200. 3000. 3500. 4000. 5000. 7500.

 10000. 10000. 10000. 7500. 7500. 7500. 4500. 3500. 3500. 3500. 3500. 3500.

 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500. 3500.

 3500.

 13970. 13364. 12790. 12268. 11732. 11224. 10660. 10060. 9428. 8892. 8122. 7890. /* 30

 7452. 7060. 6988. 6000. 6000. 6000. 6000. 6000. 6000. 5000. 2000. 1800.

 1800. 1800. 1800. 1800. 2000. 2000. 2000. 1800. 1800. 1800. 1800. 1800.

 1800. 1800. 1800. 1800. 1800. 1800. 2200. 2500. 3000. 3500. 4000. 5000.

 6000. 7500. 7500. 7000. 7000. 7000. 4000. 3500. 3000. 3000. 3000. 3000.

 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000. 3000.

 3000.

 6828. 6314. 4828. 4398. 3350. 3246. 3110. 3678. 4274. 6974. 6922. 8262. /* 31

 7026. 6482. 5400. 4952. 3150. 5000. 6000. 6000. 2000. 2000. 1800. 1800.

 1800. 1800. 1800. 1800. 1900. 1900. 1800. 1600. 1600. 1600. 1600. 1600.

 1600. 1600. 1600. 1600. 1600. 1800. 2000. 2500. 2500. 3000. 4000. 5000.

 6000. 7000. 3000. 3000. 3000. 3000. 3000. 3000. 2000. 2000. 2000. 2000.

 2000. 2000. 2000. 1800. 1500. 1500. 1500. 1500. 1500. 1500. 1500. 1500.

 1500.

 500. 500. 500. 500. 500. 500. 500. 500. 500. 986. 5400. 4952. /* 32

 3150. 2700. 2000. 1500. 2000. 4000. 6000. 6000. 1700. 1700. 1600. 1600.

 1600. 1600. 1600. 1600. 1600. 1600. 1000. 1000. 1000. 1000. 1000. 1000.

 1000. 1000. 1000. 1000. 1100. 1100. 1500. 2000. 2000. 2000. 2000. 2000.

 2000. 2200. 2200. 2200. 2200. 2200. 2200. 2000. 2000. 2000. 1000. 1000.

 700. 700. 700. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000. 1000.

 1000.

 300. 300. 300. 300. 300. 300. 300. 300. 300. 866. 1000. 1000. /* 33

 1000. 1000. 1000. 1000. 1000. 2000. 6000. 6000. 1300. 1300. 1400. 1400.

 1600. 1600. 1600. 1600. 1200. 1200. 500. 500. 500. 500. 500. 500.

 500. 500. 500. 200. 200. 200. 200. 200. 200. 200. 400. 1000.

 1500. 2200. 2200. 2200. 2200. 2200. 1800. 1800. 1600. 1600. 1000. 500.

 200. 200. 200. 200. 500. 500. 500. 500. 500. 500. 500. 500.

 500.

 200. 200. 200. 200. 200. 200. 200. 200. 200. 700. 700. 800. /* 34

 800. 800. 800. 800. 800. 2000. 6000. 6000. 800. 800. 800. 800.

 800. 800. 500. 500. 500. 500. 500. 500. 500. 400. 400. 400.

 400. 400. 150. 100. 40. 30. 30. 30. 20. 20. 20. 70.

 200. 200. 200. 50. 50. 50. 50. 50. 50. 50. 100. 100.

 150. 150. 230. 230. 230. 230. 230. 230. 230. 230. 230. 230.

 230.

 200. 200. 200. 200. 200. 200. 200. 200. 200. 200. 700. 700. /* 35

 700. 600. 600. 600. 600. 1000. 6000. 6000. 700. 600. 600. 700.

 600. 600. 600. 600. 600. 600. 500. 400. 400. 400. 400. 400.

 400. 200. 250. 70. 20. 20. 20. 20. 20. 20. 200. 200.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
68 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 200. 200. 50. 50. 50. 50. 50. 50. 50. 50. 50. 50.

 100. 100. 230. 230. 230. 230. 230. 230. 230. 230. 230. 230.

 230.

 200. 200. 200. 200. 200. 200. 200. 400. 400. 400. 400. 400. /* 36

 400. 400. 400. 400. 400. 1000. 6000. 6000. 400. 600. 700. 700.

 700. 700. 300. 300. 100. 100. 100. 100. 100. 200. 200. 200.

 200. 200. 300. 100. 20. 20. 20. 20. 20. 20. 100. 100.

 100. 100. 50. 50. 50. 50. 50. 50. 50. 50. 50. 50.

 100. 100. 100. 220. 220. 220. 220. 220. 220. 220. 220. 220.

 220.

RECHARGE INPUT PACKAGE:

 18 2.64e-09 (12F7.0) 0

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 01

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 02

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 03

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 04

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 05

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 06

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 07

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 69

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 08

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 09

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 10

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 11

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 12

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 13

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 14

 0. 5. 5. 5. 5. 5. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. /* 15

 5. 5. 5. 5. 5. 5. 5. 5. 5. 5. 5. 5.

 3. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3.

 3. 3. 3. 3. 3. 3. 3. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 4. 10. /* 16

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 4. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3.

 3. 3. 3. 3. 3. 3. 3. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
70 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 4. 10. /* 17

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 4. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3. 3.

 3. 3. 3. 3. 3. 3. 3. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 2. 2. 2. 2. 2. 0. 0. 0. 0. 0. 4. 10. /* 18

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4.

 4. 4. 4. 4. 4. 4. 4. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0.

 0.

 2. 2. 2. 2. 2. 0. 0. 0. 0. 0. 4. 10. /* 19

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4.

 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4.

 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4.

 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 4.

 4.

 4. 4. 4. 4. 2. 2. 2. 2. 2. 2. 4. 4. /* 20

 4. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 4. 4. 8. 8. 8. 8. 8. 8. 8.

 8.

 4. 4. 4. 4. 2. 2. 2. 2. 2. 2. 2. 2. /* 21

 2. 2. 2. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 12. 12. 12. 12. 12. 12. 12. 12. 12. 10.

 10. 10. 10. 4. 4. 8. 8. 8. 8. 8. 8. 8.

 8.

 8. 8. 8. 3. 2. 2. 2. 2. 2. 2. 2. 2. /* 22

 2. 2. 2. 2. 2. 4. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12.

 12. 15. 15. 15. 15. 15. 15. 15. 15. 12. 12. 12.

 10. 10. 4. 4. 4. 4. 8. 8. 8. 8. 8. 8.

 8. 

 8. 8. 8. 8. 3. 2. 2. 2. 2. 2. 2. 2. /* 23

 2. 2. 2. 2. 2. 4. 10. 12. 12. 12. 12. 12.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 10.

 10. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8.

 10. 10. 10. 10. 10. 2. 2. 2. 2. 2. 2. 2. /* 24

 2. 2. 2. 2. 2. 2. 3. 15. 15. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 12. 10.

 12. 15. 15. 15. 12. 10. 10. 10. 10. 8. 8. 8.

 8.

 12. 12. 12. 12. 10. 10. 10. 3. 3. 3. 3. 3. /* 25

 3. 3. 3. 3. 3. 3. 4. 4. 10. 10. 10. 10.

 10. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 12. 10.

 12. 15. 15. 12. 10. 10. 10. 10. 10. 8. 8. 8.

 8.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 71

 12. 12. 12. 12. 12. 12. 10. 10. 4. 4. 4. 4. /* 26

 4. 4. 4. 4. 4. 4. 4. 4. 8. 8. 8. 8.

 10. 15. 15. 18. 18. 18. 18. 18. 18. 18. 18. 18.

 18. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 18. 18. 18. 18. 18. 18. 18. 18. 18. 15. 12. 10.

 12. 15. 15. 15. 15. 15. 15. 12. 10. 8. 8. 8.

 8.

 12. 12. 12. 12. 12. 12. 12. 10. 10. 4. 4. 4. /* 27

 4. 4. 4. 4. 4. 4. 4. 4. 8. 8. 10. 10.

 10. 10. 10. 12. 15. 18. 18. 18. 18. 18. 18. 18.

 18. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 18. 18. 18. 18. 18. 18. 18. 18. 18. 18. 12. 10.

 10. 12. 15. 15. 15. 15. 15. 15. 12. 10. 8. 4.

 4.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 10. 10. 4. /* 28

 4. 4. 4. 4. 4. 4. 4. 4. 4. 4. 10. 10.

 10. 10. 10. 12. 15. 18. 18. 18. 18. 18. 18. 18.

 18. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15.

 18. 18. 18. 18. 18. 18. 18. 18. 18. 18. 18. 15.

 10. 12. 15. 15. 15. 15. 15. 15. 12. 10. 8. 4.

 4.

 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. 15. /* 29

 15. 15. 15. 15. 4. 4. 4. 4. 4. 4. 10. 12.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12.

 12. 12. 12. 12. 12. 12. 15. 15. 15. 15. 15. 15.

 18. 18. 18. 18. 18. 18. 18. 18. 18. 18. 18. 15.

 10. 12. 15. 15. 15. 15. 15. 15. 12. 10. 8. 4.

 4.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. /* 30

 12. 12. 12. 12. 12. 4. 4. 4. 4. 4. 4. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 12. 15. 15. 15. 15. 15. 15. 15. 15. 12. 10.

 10. 10. 12. 12. 12. 12. 12. 12. 12. 12. 10. 8.

 4.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. 12. /* 31

 12. 12. 12. 12. 12. 4. 4. 4. 4. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 10. 10. 10. 10. 10. 10.

 10. 10. 12. 12. 12. 12. 12. 12. 12. 12. 10. 10.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 10. 8. 4.

 4.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. /* 32

 10. 10. 10. 10. 10. 4. 4. 4. 4. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 12. 12. 12. 12. 12. 12. 12. 12. 12. 10. 8. 4.

 4.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. /* 33

 10. 10. 10. 10. 10. 4. 4. 4. 4. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. /* 34

 10. 10. 10. 10. 10. 4. 4. 4. 4. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10. 10.

 10.

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
72 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. /* 35

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. /* 36

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8. 8.

 8.

WELL PACKAGE (INJECTION WELLS ALONG SOUTHERN MODEL BOUNDARY AND ESTIMATED WITHDRAWALS

FROM PUBLIC SUPPLY, INDUSTRIAL, AND IRRIGATION WELLS FOR MARCH 1995 HYDROLOGIC

CONDITIONS)

 70 -3 

 70 /* Q (cfs)

 1 36 47 0.05 /*Injection well Quebrada Hicatea

 1 36 48 0.10 /*Injection well Quebrada Hicatea

 1 36 49 0.05 /*Injection well Quebrada Hicatea

 1 35 48 0.10 /*Injection well Quebrada Hicatea

 1 35 49 0.05 /*Injection well Quebrada Hicatea

 1 34 49 0.10 /*Injection well Quebrada Hicatea

 1 34 50 0.05 /*Injection well Quebrada Hicatea

 1 34 51 0.05 /*Injection well Quebrada Hicatea

 1 33 50 0.05 /*Injection well Quebrada Hicatea

 1 33 51 0.05 /*Injection well Quebrada Hicatea

 1 34 34 0.12 /*Injection well Quebrada El Salto

 1 34 35 0.12 /*Injection well Quebrada El Salto

 1 34 36 0.12 /*Injection well Quebrada El Salto

 1 36 37 0.12 /*Injection well Quebrada El Salto

 1 34 40 0.08 /*Injection well Pugnado Adentro

 1 34 41 0.08 /*Injection well Pugnado Adentro

 1 34 42 0.08 /*Injection well Pugnado Adentro

 1 34 43 0.08 /*Injection well Pugnado Adentro

 1 34 44 0.08 /*Injection well Pugnado Adentro

 1 34 45 0.08 /*Injection well Pugnado Adentro

 1 26 31 -1.25 /*Coto Sur 1 (PS) 

 1 25 38 -0.00 /*Coto Sur 2 (PS

 1 26 35 -0.71 /*Coto Sur 5 (PS)

 1 26 33 -0.84 /*Coto Sur 6 (PS)

 1 29 24 -0.36 /*Coto Sur 4 (PS)

 1 25 31 -0.00 /*Coto Sur 3 (PS)

 1 26 30 -0.26 /*Roche (Ind)

 1 28 25 -0.41 /*Escal Fullery (PS)

 1 22 28 -0.39 /*Davis & Geck N & S (Ind)

 1 22 30 -1.12 /*Schering Plough (Ind)

 1 24 22 -0.94 /*Oficina PRASA (PS)

 1 23 25 -1.22 /*Cordova Davilla (PS)

 1 25 40 -0.00 /*Pugnado 3 (PS)

 1 20 58 -0.45 /*Vega Baja 1 (PS)

 1 18 52 -0.62 /*Vega Baja 2 (PS)

 1 20 53 -1.80 /*Vega Baja 3 (PS)

 1 20 54 -0.60 /*Vega Baja 4 (PS)

 1 23 52 -0.87 /*Alturas (PS)

 1 21 50 -0.87 /*Algarrobo (PS)

 1 21 47 -0.42 /*Agregado (Mn)

 1 22 42 -0.47 /*Sobrino (PS)

 1 25 51 -0.70 /*Pugnado Afuera 1 (PS)

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 73

 1 26 50 -0.80 /*Pugnado Afuera 2 (PS)

 1 21 40 -0.20 /*Coto Norte 3 (PS)

 1 21 32 -0.23 /*Atenas (PS)

 1 23 33 -0.11 /*Eaton Labs (Ind)

 1 23 35 -0.11 /*Orto Lab (Ind)

 1 17 22 -0.70 /*Rabanos (PS)

 1 13 21 -0.83 /*Boquillas (PS)

 1 18 20 -0.39 /*Cruz Rosa Rivas (PS)

 1 31 64 -0.19 /*Almirante 2 (PS)

 1 31 66 -0.22 /*Arraiza (PS)

 1 25 63 -0.36 /*Almirante 3 (PS)

 1 21 66 -1.09 /*Monserrate (PS)

 1 26 19 -2.03 /*Manati 1 (PS)

 1 26 18 -1.87 /*Manati 2 (PS)

 1 25 16 -0.00 /*Safety Kleen (Ind)

 1 27 56 -0.25 /*Villa Pinares (PS)

 1 17 70 -0.07 /*Warner Lambert 1 (Ind)

 1 18 70 -0.07 /*Warner Lambert 2 (Ind)

 1 20 1 -0.81 /*Fortuna (PS)

 1 19 70 -0.31 /*Sabana Hoyos 3 (PS)

 1 14 22 -0.11 /*Cubano Jacobo (Irr)

 1 26 33 -0.05 /*Coto Sur Warehouse (Irr)

 1 35 20 -0.08 /*Monserrate Sur (Irr)

 1 22 33 -0.00 /*Coto Norte 1 (PS)

 1 17 73 -0.16 /*Sabana Hoyos 2 (PS)

 1 23 17 -0.02 /*Calaf (Irr)

 1 23 72 -0.99 /*Santa Rosa 2 (PS)

 1 21 39 -0.00 /*Coto Norte 2 (PS)

DRAIN PACKAGE INPUT FILE:

 14 -6

 14

 1 12 17 0.500E+00 2000.E+00 /*Springs Mameyes

 1 12 14 0.500E+00 2000.E+00 /*Tierras Nuevas

 1 12 15 0.500E+00 2000.E+00 /*Tierras Nuevas

 1 13 14 0.800E+00 2000.E+00 /*Tierras Nuevas

 1 15 32 1.500E+00 2000.E+00 /*Laguna South

 1 15 33 1.500E+00 2000.E+00 /*Laguna South

 1 16 34 1.500E+00 2000.E+00 /*Laguna South

 1 15 35 1.500E+00 2000.E+00 /*Laguna South

 1 15 36 1.500E+00 2000.E+00 /*Laguna South

 1 18 53 4.300E+00 2000.E+00 /*Ojo de Agua

 1 18 54 4.300E+00 2000.E+00 /*Ojo de Agua

 1 26 9 5.500E+00 2000.E+00 /*Ojo de Guillo

 1 27 8 5.500E+00 2000.E+00 /*Ojo de Guillo

 1 27 9 5.500E+00 2000.E+00 /*Ojo de Guillo

RIVER PACKAGE INPUT FILE:

 289 -6 /* RIVERBED BOTTOM 

 289 /* STAGE CONDUCTANCE ELEV.

 1 8 7 0.500E+00 1.000E-01 -2.000E+0 /*Rio Grande de Manati

 1 8 8 0.500E+00 1.000E-01 -2.000E+0 /*Rio Grande de Manati

 1 9 8 0.500E+00 1.000E-01 -2.000E+0 /*Rio Grande de Manati

 1 10 8 0.500E+00 1.000E-01 -2.000E+0 /*Rio Grande de Manati

 1 11 8 0.500E+00 1.000E-01 -2.000E+0 /*Rio Grande de Manati

 1 12 8 0.500E+00 1.000E-01 -2.000E+0 /*Rio Grande de Manati

 1 13 8 1.500E-01 1.000E-01 -1.000E+0 /*Rio Grande de Manati

 1 14 7 3.500E-01 1.000E-01 -1.000E+0 /*Rio Grande de Manati

 1 15 6 5.500E-01 1.000E-01 -1.000E+0 /*Rio Grande de Manati

 1 16 6 6.000E-01 1.000E-01 -1.000E+0 /*Rio Grande de Manati

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
74 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 1 16 7 7.000E-01 1.000E-01 -1.000E+0 /*Rio Grande de Manati

 1 15 8 1.050E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 15 9 1.170E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 16 10 1.250E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 17 9 1.330E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 18 8 1.440E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 18 7 1.500E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 18 6 1.700E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 19 6 1.800E+00 1.000E-01 0.000E+00 /*Rio Grande de Manati

 1 19 5 2.500E+00 1.000E-01 1.000E+00 /*Rio Grande de Manati

 1 20 5 2.800E+00 1.000E-01 1.000E+00 /*Rio Grande de Manati

 1 20 6 2.900E+00 1.000E-01 1.000E+00 /*Rio Grande de Manati

 1 20 7 3.100E+00 1.000E-01 1.000E+00 /*Rio Grande de Manati

 1 21 7 3.120E+00 1.000E-01 1.000E+00 /*Rio Grande de Manati

 1 21 6 3.140E+00 1.000E-01 1.000E+00 /*Rio Grande de Manati

 1 22 6 3.200E+00 3.000E-01 1.000E+00 /*Rio Grande de Manati

 1 23 6 3.500E+00 3.000E-01 1.000E+00 /*Rio Grande de Manati

 1 23 7 3.630E+00 3.000E-01 1.000E+00 /*Rio Grande de Manati

 1 23 8 3.790E+00 3.000E-01 1.000E+00 /*Rio Grande de Manati

 1 22 8 3.960E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 21 8 4.050E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 21 9 4.250E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 22 9 4.350E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 23 9 4.500E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 24 9 4.700E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 24 10 4.910E+00 3.000E-01 2.000E+00 /*Rio Grande de Manati

 1 24 11 5.000E+00 3.000E-01 3.000E+00 /*Rio Grande de Manati

 1 25 11 5.050E+00 3.000E-01 3.000E+00 /*Rio Grande de Manati

 1 25 10 5.350E+00 3.000E-01 3.000E+00 /*Rio Grande de Manati

 1 26 10 5.800E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 26 11 6.000E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 27 11 6.270E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 27 12 6.430E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 28 12 6.600E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 28 13 6.900E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 27 13 7.100E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 27 14 7.400E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 26 14 7.550E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 26 15 7.650E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 26 16 7.800E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 27 16 8.000E+00 4.000E-01 3.000E+00 /*Rio Grande de Manati

 1 28 16 8.500E+00 4.000E-01 4.000E+00 /*Rio Grande de Manati

 1 29 16 8.700E+00 4.000E-01 4.000E+00 /*Rio Grande de Manati

 1 29 17 9.800E+00 4.000E-01 5.000E+00 /*Rio Grande de Manati

 1 30 17 1.080E+01 4.000E-01 6.500E+00 /*Rio Grande de Manati

 1 30 18 1.408E+01 4.000E-01 7.500E+00 /*Rio Grande de Manati

 1 29 18 1.550E+01 4.000E-01 1.050E+01 /*Rio Grande de Manati

 1 28 18 1.780E+01 6.000E-01 1.180E+01 /*Rio Grande de Manati

 1 28 19 2.020E+01 6.000E-01 1.200E+01 /*Rio Grande de Manati

 1 28 20 2.250E+01 6.000E-01 1.330E+01 /*Rio Grande de Manati

 1 28 21 2.500E+01 6.000E-01 1.460E+01 /*Rio Grande de Manati

 1 29 21 2.600E+01 6.000E-01 1.540E+01 /*Rio Grande de Manati

 1 30 21 2.700E+01 6.000E-01 1.600E+01 /*Rio Grande de Manati

 1 31 21 2.750E+01 6.000E-01 1.650E+01 /*Rio Grande de Manati

 1 32 21 2.800E+01 6.000E-01 1.800E+01 /*Rio Grande de Manati

 1 32 20 2.852E+01 6.000E-01 1.900E+01 /*Rio Grande de Manati

 1 32 19 2.900E+01 6.000E-01 2.000E+01 /*Rio Grande de Manati

 1 33 19 2.950E+01 6.000E-01 2.200E+01 /*Rio Grande de Manati

 1 34 18 3.000E+01 6.000E-01 2.400E+01 /*Rio Grande de Manati

 1 35 19 3.050E+01 6.000E-01 2.500E+01 /*Rio Grande de Manati

 1 36 19 3.100E+01 6.000E-01 2.800E+01 /*Rio Grande de Manati

 1 6 60 0.500E+00 3.000E-02 -9.000E+0 /*Cano Las Pozas

 1 7 60 0.500E+00 3.000E-02 -8.500E+0 /*Cano Las Pozas

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 75

 1 8 60 5.000E-01 3.000E-02 -6.000E+0 /*Cano Las Pozas

 1 8 61 5.000E-01 3.000E-02 -6.000E+0 /*Cano Las Pozas

 1 9 60 1.000E+00 3.000E-02 -3.000E+0 /*Cano Las Pozas

 1 9 61 1.000E+00 3.000E-02 -3.000E+0 /*Cano Las Pozas

 1 10 60 1.500E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 11 60 1.500E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 12 59 1.500E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 13 60 2.000E+00 3.000E-02 -0.500E+0 /*Cano Las Pozas

 1 14 60 2.000E+00 3.000E-02 -0.500E+0 /*Cano Las Pozas

 1 15 60 2.000E+00 3.000E-02 -0.500E+0 /*Cano Las Pozas

 1 16 61 2.500E+00 3.000E-02 -0.000E+0 /*Cano Las Pozas

 1 17 61 2.500E+00 3.000E-02 -0.000E+0 /*Cano Las Pozas

 1 18 61 2.500E+00 3.000E-02 -0.000E+0 /*Cano Las Pozas

 1 13 58 2.000E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 13 57 2.000E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 14 57 2.000E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 15 57 2.500E+00 3.000E-02 -1.000E+0 /*Cano Las Pozas

 1 6 59 5.000E-01 3.000E-02 -6.000E+0 /*Cano Cabo Caribe

 1 6 58 5.000E-01 3.000E-02 -6.000E+0 /*Cano Cabo Caribe

 1 7 58 1.000E+00 3.000E-02 -4.000E+0 /*Cano Cabo Caribe

 1 7 57 1.000E+00 3.000E-02 -4.000E+0 /*Cano Cabo Caribe

 1 7 56 1.000E+00 3.000E-02 -4.000E+0 /*Cano Cabo Caribe

 1 8 55 1.500E+00 3.000E-02 -2.000E+0 /*Cano Cabo Caribe

 1 9 55 1.500E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 10 55 1.500E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 10 54 1.600E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 11 54 1.700E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 11 53 1.600E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 10 52 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 10 51 1.700E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 11 51 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 12 51 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 12 52 1.800E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 13 51 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 13 52 1.900E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 14 51 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 14 50 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 14 52 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 14 49 2.000E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 13 49 1.800E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe 

 1 11 49 1.900E+00 3.000E-01 -2.000E+0 /*Cano Cabo Caribe

 1 9 37 0.000E+00 3.000E-01 -2.000E+0 /*Laguna Tortuguero Outlet

 1 10 38 0.300E+00 3.000E-01 -2.000E+0 /*Laguna Tortuguero Outlet

 1 11 38 0.600E+00 3.000E-01 -2.000E+0 /*Laguna Tortuguero Outlet

 1 12 31 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 12 32 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 30 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 31 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 32 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 33 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 37 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 38 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 39 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 40 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 41 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 42 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 43 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 44 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 13 45 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 36 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 37 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 39 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 40 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
76 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 1 14 41 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 42 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 43 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 14 44 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 15 43 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 15 44 0.900E+00 0.120E+00 -2.000E+0 /*Laguna Tortuguero

 1 5 61 0.500E+00 1.000E-01 -9.500E+0 /*Rio Cibuco 

 1 6 61 0.500E+00 1.000E-01 -9.000E+0 /*Rio Cibuco

 1 6 62 0.500E+00 1.000E-01 -8.500E+0 /*Rio Cibuco

 1 7 62 0.500E+00 1.000E-01 -8.000E+0 /*Rio Cibuco

 1 8 63 0.500E+00 1.000E-01 -7.500E+0 /*Rio Cibuco

 1 8 64 0.500E+00 1.000E-01 -7.000E+0 /*Rio Cibuco

 1 8 65 0.500E+00 1.000E-01 -6.500E+0 /*Rio Cibuco

 1 8 66 1.000E+00 1.000E-01 -5.000E+0 /*Rio Cibuco

 1 8 67 1.000E+00 1.000E-01 -4.000E+0 /*Rio Cibuco

 1 9 68 1.500E+00 1.000E-01 -3.000E+0 /*Rio Cibuco

 1 10 68 1.500E+00 1.000E-01 -2.500E+0 /*Rio Cibuco

 1 11 68 2.000E+00 1.000E-01 -2.000E+0 /*Rio Cibuco

 1 11 67 2.500E+00 1.000E-01 -1.500E+0 /*Rio Cibuco

 1 12 67 2.500E+00 1.000E-01 -1.000E+0 /*Rio Cibuco

 1 12 66 2.500E+00 1.000E-01 -5.000E-1 /*Rio Cibuco

 1 13 66 2.500E+00 1.000E-01 0.000E+00 /*Rio Cibuco

 1 14 66 3.000E+00 5.000E-01 5.000E-01 /*Rio Cibuco

 1 14 65 3.000E+00 5.000E-01 8.000E-01 /*Rio Cibuco

 1 15 65 3.500E+00 5.000E-02 1.000E+00 /*Rio Cibuco

 1 15 64 4.500E+00 5.000E-02 1.500E+00 /*Rio Cibuco

 1 16 64 5.000E+00 5.000E-02 2.000E+00 /*Rio Cibuco

 1 16 63 5.500E+00 5.000E-02 2.500E+00 /*Rio Cibuco

 1 17 63 6.000E+00 5.000E-02 4.000E+00 /*Rio Cibuco

 1 17 62 9.000E+00 5.000E-02 6.500E+00 /*Rio Cibuco

 1 18 62 1.100E+01 5.000E-02 8.000E+00 /*Rio Cibuco

 1 19 62 1.250E+01 1.100E-01 9.000E+00 /*Rio Cibuco

 1 19 63 1.300E+01 1.100E-01 9.000E+00 /*Rio Cibuco

 1 20 64 1.350E+01 1.100E-01 9.000E+00 /*Rio Cibuco

 1 20 65 1.400E+01 1.100E-01 1.000E+01 /*Rio Cibuco

 1 21 65 1.450E+01 1.100E-01 1.100E+01 /*Rio Cibuco

 1 21 66 1.500E+01 1.100E-01 1.300E+01 /*Rio Cibuco

 1 22 66 1.650E+01 1.100E-01 1.400E+01 /*Rio Cibuco

 1 23 67 1.800E+01 1.100E-01 1.550E+01 /*Rio Cibuco

 1 24 67 1.900E+01 1.100E-01 1.650E+01 /*Rio Cibuco

 1 25 67 2.000E+01 1.100E-01 1.750E+01 /*Rio Cibuco

 1 25 68 2.100E+01 1.100E-01 1.850E+01 /*Rio Cibuco

 1 25 69 2.250E+01 1.100E-01 2.000E+01 /*Rio Cibuco

 1 25 70 2.350E+01 3.000E-02 2.150E+01 /*Rio Cibuco

 1 25 71 2.400E+01 3.000E-02 2.200E+01 /*Rio Cibuco

 1 25 72 2.500E+01 3.000E-02 2.250E+01 /*Rio Cibuco

 1 26 72 2.800E+01 3.000E-02 2.300E+01 /*Rio Cibuco

 1 27 72 3.000E+01 3.000E-02 2.600E+01 /*Rio Cibuco

 1 28 72 3.050E+01 3.000E-02 2.850E+01 /*Rio Cibuco

 1 28 73 3.300E+01 3.000E-02 3.100E+01 /*Rio Cibuco

 1 21 65 1.400E+01 4.000E-02 1.200E+01 /*Rio Indio 

 1 22 65 1.450E+01 4.000E-02 1.150E+01 /*Rio Indio

 1 22 64 1.500E+01 4.000E-02 1.100E+01 /*Rio Indio

 1 22 63 1.600E+01 4.000E-02 1.400E+01 /*Rio Indio

 1 23 63 1.700E+01 4.000E-02 1.500E+01 /*Rio Indio

 1 23 62 1.800E+01 4.000E-02 1.600E+01 /*Rio Indio

 1 23 61 1.950E+01 4.000E-02 1.750E+01 /*Rio Indio

 1 24 61 2.100E+01 4.000E-02 1.900E+01 /*Rio Indio

 1 24 60 2.300E+01 4.000E-02 2.100E+01 /*Rio Indio

 1 25 60 2.450E+01 4.000E-02 2.250E+01 /*Rio Indio

 1 26 60 2.600E+01 4.000E-02 2.450E+01 /*Rio Indio

 1 27 60 2.700E+01 4.000E-02 2.500E+01 /*Rio Indio

 1 27 61 2.800E+01 4.000E-02 2.600E+01 /*Rio Indio

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 77

 1 27 62 3.000E+01 4.000E-02 2.800E+01 /*Rio Indio

 1 28 62 3.200E+01 4.000E-02 3.000E+01 /*Rio Indio

 1 29 61 3.300E+01 4.000E-02 3.100E+01 /*Rio Indio

 1 29 62 3.400E+01 4.000E-02 3.200E+01 /*Rio Indio

 1 30 62 3.500E+01 4.000E-02 3.300E+01 /*Rio Indio

 1 30 61 3.600E+01 4.000E-02 3.400E+01 /*Rio Indio

 1 30 60 3.700E+01 4.000E-02 3.500E+01 /*Rio Indio

 1 31 60 3.800E+01 4.000E-02 3.600E+01 /*Rio Indio

 1 31 59 3.900E+01 4.000E-02 3.700E+01 /*Rio Indio

 1 32 59 4.000E+01 4.000E-02 3.800E+01 /*Rio Indio

 1 32 58 4.100E+01 4.000E-02 3.900E+01 /*Rio Indio

 1 33 57 4.200E+01 4.000E-02 4.000E+01 /*Rio Indio

 1 34 57 4.300E+01 4.000E-02 4.100E+01 /*Rio Indio

 1 34 56 4.550E+01 4.000E-02 4.400E+01 /*Rio Indio

 1 35 56 4.800E+01 4.000E-02 4.650E+01 /*Rio Indio

 1 35 55 4.900E+01 4.000E-02 4.750E+01 /*Rio Indio

 1 36 55 5.000E+01 4.000E-02 4.850E+01 /*Rio Indio

 1 3 1 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 3 2 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 4 3 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 5 4 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 5 5 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 6 6 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 6 7 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 5 8 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 5 9 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 5 10 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 5 11 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 6 12 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 6 13 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 14 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 15 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 16 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 17 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 18 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 19 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 20 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 21 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 7 22 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 8 23 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 8 24 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 8 25 0.000E+00 1.000E+02 -2.000E+0 /*Atlantic Ocean

 1 8 26 0.000E+00 1.000E+02 -2.000E+0 /*Atlantic Ocean

 1 8 27 0.000E+00 1.000E+02 -2.000E+0 /*Atlantic Ocean

 1 8 28 0.000E+00 1.000E+02 -2.000E+0 /*Atlantic Ocean

 1 8 29 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 8 30 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 8 31 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 7 32 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 7 33 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 6 34 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 5 35 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 4 36 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 37 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 38 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 39 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 40 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
78 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

 1 3 41 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 42 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 43 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 44 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 45 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 46 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 47 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 48 0.000E+00 3.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 49 0.000E+00 1.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 50 0.000E+00 1.000E+02 -2.000E+0 /*Atlantic Ocean

 1 3 51 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 3 52 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 3 53 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 2 54 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 2 55 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 3 56 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 3 57 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 4 58 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 4 59 0.000E+00 1.000E-01 -2.000E+0 /*Atlantic Ocean

 1 4 60 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 61 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 62 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 63 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 64 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 5 65 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 5 66 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 67 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 68 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 4 69 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 5 70 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 5 71 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 5 72 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

 1 6 73 0.000E+00 3.000E+01 -2.000E+0 /*Atlantic Ocean

STRONGLY IMPLICIT PROCEDURE INPUT FILE:

 100 5 

 1.0 0.01 1

OUTPUT CONTROL INPUT FILE:

 4 0 30 0 IHEDFM,IDDNFM,IHEDUN,IDDNUN

 1 1 1 1 1,1,IBUDFL,ICBCFL: PER. 1 STEP 1

 1 0 1 0 Hdpr,Ddpr,Hdsv,Ddsv

Appendix 1. Input files for the Manatí-Vega Baja model of the upper aquifer—Continued.
Appendix 79

Appendix 2a. Summary of sensitivity of ground-water recharge.

[Outlined values indicate final calibration results for 1995 hydrologic conditions. Results consist of the difference between observed and 

computed head, the percentage difference within a specified range, and the volumetric budget terms in cubic feet per second. Multiplier 

applied to the calibrated rate values are underlined. Refer to fig. 16 for control-cell location.]
80 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Appendix 2b. Summary of sensitivity analysis for simulated injection and pumping rates at wells.
Appendix 81

Appendix 2c. Summary of sensitivity analysis of aquifer transmissivity.
82 Simulation of Flow in the Upper North Coast Limestone Aquifer, Manatí-Vega Baja Area, Puerto Rico

Appendix 2d. Summary of sensitivity of riverbed conductance.