#  Evaluation of Tracer Tests on the Upper Santa Clara River, Los Angeles and Ventura Counties, California, during October 1999 and May 2000

***By*Marisa H. Cox,Gregory O. Mendez,Charles R. Kratzer,and Eric G. Reichard**

 

 U.S. GEOLOGICAL SURVEY 

 Water–Resources Investigations Report 03-4277 

Sacramento, California 2003 

 Prepared in      cooperation with the

Los Angeles County Sanitation District

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The interaction of surface water and hyporheic water   along the Santa Clara River in Los Angeles and Ventura Counties, California,   was evaluated by conducting tracer tests and analyzing water-quality data under   different flow conditions in October 1999 and May 2000. Tracer and water-quality   samples were collected at multiple river and hyporheic sites as well as at the   Los Angeles County Sanitation Districts Saugus and Valencia Water Reclamation   Plants. These water reclamation plants provide the main source of base flow   in the river. Rhodamine WT dye was injected into the river to determine river   traveltimes and to indicate when Lagrangian water-quality sampling could be   performed at each site. Sodium bromide was injected into the river at a constant   rate at the water reclamation plants to evaluate the surface-water and shallow   ground-water interactions in the hyporheic zone.

     In the upper reach of the study area, which extends   2.9 river miles downstream from the Saugus Water Reclamation Plant, traveltime   was 3.2 hours during May 2000. In the lower reach, which extends 14.1 river   miles downstream from the Valencia Water Reclamation Plant, traveltime was 9.6   hours during October 1999 and 7.1 hours during May 2000. The sodium bromide   tracer was detected at both hyporheic locations sampled during October 1999,   and at two of the three hyporheic locations sampled during May 2000. On the   basis of Rhodamine dye tests, flow curves were constructed from the discharge   measurements in the Valencia reach. Flow-curve results indicate net gains in   flow throughout most, but not all, of the upper parts of the reach and net losses   in flow at the lower part of the reach.

Lagrangian water-quality sampling provides information on the changes in chemistry   as the water flows downstream from the water reclamation plants. Along both   reaches there is an increase in sulfate (40-60 mg/L in the Saugus reach and   160 mg/L in the Valencia reach) and a decrease in chloride (about 45 mg/L in   the Saugus reach and about 10 mg/L in the Valencia reach). The increasing sulfate   concentrations are consistent with discharge of higher sulfate ground water   into the river. Along both reaches there is a trend of decreasing ammonia and   slightly increasing nitrate concentrations. This trend is consistent with nitrification.  

Samples were also analyzed for numerous compounds associated with wastewater,   but analysis focused on four indicators. Concentrations of wastewater indicators   in the Santa Clara River were low and decreased downstream from the reclamation   plants.

There is general consistency between the chemical and   tracer data collected from the hyporheic and the river-aquifer flow regime within   a reach. The water quality at the hyporheic site in a gaining reach of the river   resembled that of the local ground water and no wastewater indicators or injected   tracers were observed; whereas, the water quality at the hyporheic sites in   a losing reach of the river resembled the water quality of the river at the   corresponding river site, and injected tracers were observed.
CONTENTS
Abstract

Introduction

 Purpose, Scope, and Approach

 Acknowledgments

Description of Study Area

Hydrology

Land Use

Approach

Tracer Techniques

Water-Quality Sampling and Analysis

Streamflow Analysis

Flow Conditions

October 1999

May 2000

Comparison of October 1999 and May 2000 Data

Slug Injection Tracer Test Results

October 1999

May 2000

Comparison of October 1999 and May 2000 Data

Flow Curves

Constant-Rate Injection Tracer Reults

October 1999

May 2000

Comparison of October 1999 and May 2000 Data

Water Quality

October 1999

May 2000

Comparison of October 1999 and May 2000 Data

Wastewater Indicators

October 1999

May 2000

Comparison of October 1999 and May 2000 Data

Summary

References Cited

Appendixes

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