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Open-File Report 2014–1101

Stable Isotope (δ18O and δ2H) Data for Precipitation, Stream Water, and Groundwater in Puerto Rico

By Martha A. Scholl, Angel Torres-Sanchez, and Manuel Rosario-Torres

Thumbnail of and link to report PDF (1.31 MB)Abstract

Puerto Rico is located in the northeastern Caribbean Sea (18.2 °N, 66.3 °W), with the Atlantic Ocean on its northern coast. The U.S. Geological Survey’s Water, Energy, and Biogeochemical Budgets (WEBB) program study area in which most of these data were collected comprises the El Yunque National Forest and surrounding area of eastern Puerto Rico. Samples were collected in two forested watersheds, the Rio Mameyes and the Rio Icacos/Rio Blanco, on opposite sides of a ridge in the Luquillo Mountains on the eastern end of the island (fig. 1). Elevation in both watersheds ranges from sea level to approximately 1,000 meters (m). Near sea level, land use is mixed pasture, moist forest, and residential, grading to completely forested within the boundaries of El Yunque National Forest. Forest type changes with elevation from tabonuco to palo colorado to sierra palm to cloud forest above approximately 950 m (Murphy and others, 2012). The Rio Mameyes watershed is oriented north-northeast, and the basin is underlain by volcaniclastic bedrock (basaltic to andesitic volcanic sandstone/mudstone/conglomerate/breccia). The Rio Icacos/Rio Blanco watershed is oriented south-southeast. The Rio Icacos is one of the headwaters of the Rio Blanco and is underlain by quartz diorite. The lower Rio Blanco basin is underlain by andesitic volcaniclastic bedrock. This report also contains a long-term rain isotope dataset from the San Agustin site, in north-central Puerto Rico (fig. 1).

Puerto Rico has a tropical climate dominated by easterly trade winds, and seasonal climate patterns affect the hydrology of the study area. The summer wet season is characterized by convective precipitation from tropical easterly waves, troughs, and cyclonic low-pressure systems, including tropical storms and hurricanes; in contrast, the drier winter season is characterized by trade-wind showers and frontal systems. The highest single-event rainfall totals tend to be associated with tropical storms, hurricanes, and cold fronts, although frequent low-intensity orographic showers occur throughout the year in the mountains. The stable isotope signatures of rainfall (δ2H and δ18O) are broadly correlated with the weather type that produced the rainfall (Scholl and others, 2009; Scholl and Murphy, 2014).

First posted August 14, 2014

For additional information, contact:
Branch Chief, National Research Program
Eastern Branch
U.S. Geological Survey
432 National Center
Reston, Virginia 20192
http://water.usgs.gov/nrp/

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Suggested citation:

Scholl, M.A., Torres-Sanchez, A., and Rosario-Torres, M., 2014, Stable isotope (δ18O and δ2H) data for precipitation, stream water, and groundwater in Puerto Rico: U.S. Geological Survey Open-File Report 2014–1101, 29 p., https://dx.doi.org/10.3133/ofr20141101.

ISSN 2331-4258 (online)



Contents

Introduction

Methods

Stable Isotope Data

Acknowledgments

References Cited


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