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Sanitary quality of surface water during base-flow conditions in the Municipality of Caguas, Puerto Rico, 2014–15: A comparison with results from a similar 1997–99 study

Scientific Investigations Report 2017-5045

Prepared in cooperation with the Autonomous Municipality of Caguas
By:
and
https://doi.org/10.3133/sir20175045

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Abstract

A study was conducted in 2014–15 by the U.S. Geological Survey (USGS), in cooperation with the Municipality of Caguas, to determine if changes in the stream sanitary quality during base-flow conditions have occurred since 1997–99, when a similar study was completed by the USGS. Water samples were collected for the current study during two synoptic surveys in 2014 and 2015. Water samples were analyzed for fecal and total coliform bacteria, nitrate plus nitrite as nitrogen, nitrogen and oxygen isotopes of nitrate, and human health and pharmaceutical products. Water sampling occurred at 39 stream locations used during the 1997–99 study by the USGS and at 11 additional sites. A total of 151 stream miles were classified on the basis of fecal and total coliform bacteria results.

The overall spatial pattern of the sanitary quality of surface water during 2014–15 is similar to the pattern observed in 1997–99 in relation to the standards adopted by the Puerto Rico Environmental Quality Board in 1990. Surface water at most of the water-sampling sites exceeded the current standard for fecal coliform of 200 colonies per 100 milliliters adopted by the Puerto Rico Environmental Quality Board in 2010. The poorest sanitary quality was within the urban area of the Municipality of Caguas, particularly in urban stream reaches of Río Caguitas and in rural and suburban reaches bordered by houses in high density that either have inadequate septic tanks or discharge domestic wastewater directly into the stream channels. The best sanitary quality occurred in areas having little or no human development, such as in the wards of San Salvador and Beatriz to the south and southwest of Caguas, respectively. The concentration of nitrate plus nitrite as nitrogen ranged from 0.02 to 9.0 milligrams per liter, and did not exceed the U.S. Environmental Protection Agency drinking-water standard for nitrate as nitrogen of 10 milligrams per liter. The composition of nitrogen and oxygen isotopes of nitrate indicates that the origin of nitrate in the streams is most likely animal and human waste. A baseline was established for the concentrations of selected human health and pharmaceutical products at stations in some of the streams within the Municipality of Caguas. Thirty-eight human health and pharmaceutical products were present at or above the measurement detection level.

Suggested Citation

Rodríguez-Martínez, Jesús, and Guzmán-Ríos, Senén, 2017, Sanitary quality of surface water during base-flow conditions in the Municipality of Caguas, Puerto Rico, 2014–15: A comparison with results from a similar 1997–99 study: U.S. Geological Survey Scientific Investigations Report 2017–5045, 20 p., https://doi.org/10.3133/sir20175045.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods of Study
  • Sanitary Quality of Surface Water During Base-Flow Conditions
  • Summary and Conclusions
  • References Cited
  • Appendix 1
  • Appendix 2

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Sanitary quality of surface water during base-flow conditions in the Municipality of Caguas, Puerto Rico, 2014–15: A comparison with results from a similar 1997–99 study
Series title:
Scientific Investigations Report
Series number:
2017-5045
DOI:
10.3133/sir20175045
Year Published:
2017
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Caribbean Water Science Center
Description:
Report: vii, 20 p.; Plate: 20.66 x 40.73 inches
State:
Puerto Rico
City:
Caguas
Online Only (Y/N):
Y
Additional Online Files (Y/N):
Y