Skip Links

USGS - science for a changing world

Water-Resources Investigations Report 99-4118

Prepared in cooperation with the Republic of Palau

Storage Capacity and Water Quality of Lake Ngardok, Babeldaob Island, Republic of Palau, 1996–98

By Chiu Wang Yeung and Michael F. Wong

Thumbnail of publication and link to PDF (383 kB)

A bathymetric survey conducted during March and April, 1996, determined the total storage capacity Lake Ngardok to be between 90 and 168 acre-feet. Elevation-surface area and elevationcapacity curves summarizing the current relations among elevation, surface area, and storage capacity were created from the bathymetric map. Rainfall and lake-elevation data collected from April 1996 to March 1998 indicated that lake levels correlated to rainfall values with lake elevation rising rapidly in response to heavy rainfall and then returning to normal levels within a few days. Mean lake elevation for the 22 month period of data was 59.5 feet which gives a mean storage capacity of 107 acrefeet and a mean surface area of 24.1 acre. A floating mat of reeds, which covered 58 percent of the lake surface area at the time of the bathymetric survey, makes true storage capacity difficult to estimate.

Water-quality sampling during April 1996 and November 1997 indicated that no U.S. Environmental Protection Agency primary drinking-water standards were violated for analyzed organic and inorganic compounds and radionuclides. With suitable biological treatment, the lake water could be used for drinking-water purposes. Temperature and dissolved oxygen measurements indicated that Lake Ngardok is stratified. Given that air temperature on Palau exhibits little seasonal variation, it is likely that this pattern of stratification is persistent. As a result, complete mixing of the lake is probably rare. Near anaerobic conditions exist at the lake bottom. Low dissolved oxygen (3.2 milligrams per liter) measured at the outflow indicated that water flowing past the outflow was from the deep oxygen-depleted depths of the lake.

For additional information contact:

District Chief
U.S. Geological Survey
677 Ala Moana Blvd., Suite 415
Honolulu, HI 96813

http://hi.water.usgs.gov/

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Yeung, C.W. and Wong, M.F., 1999, Storage capacity and water quality of Lake Ngardok, Babeldaob Island, Republic of Palau, 1996–98: U.S. Geological Survey Water-Resources Investigations Report 99-4118, 26 p.



Contents

Abstract

Introduction

Description of Study Area

Data-Collection Methods

Storage Capacity

Water Quality

Summary

References cited


Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo USA.gov logo U.S. Department of the Interior | U.S. Geological Survey
URL: http://pubsdata.usgs.gov/pubs/wri/wri99-4118/index.html
Page Contact Information: GS Pubs Web Contact
Page Last Modified: Wednesday, 07-Dec-2016 13:37:33 EST