USGS Scientific Investigations Report 2006–5152

Environmental Setting of the Lower Merced River Basin, California

By Jo Ann M. Gronberg and Charles R. Kratzer

 

Sacramento, California 2006



NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

Revised February, 2007 (Revision History)

Complete accessible text of report (3.8 MB PDF)

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Abstract

    In 1991, the U.S. Geological Survey began to study the effects of natural and anthropogenic influences on the quality of ground water, surface water, biology, and ecology as part of the National Water-Quality Assessment (NAWQA) Program. As part of this program, the San Joaquin–Tulare Basins study unit is assessing parts of the lower Merced River Basin, California. This report provides descriptions of natural and anthropogenic features of this basin as background information to assess the influence of these and other factors on water quality. The lower Merced River Basin, which encompasses the Mustang Creek Subbasin, gently slopes from the northeast to the southwest toward the San Joaquin River. The arid to semiarid climate is characterized by hot summers (highs of mid 90 degrees Fahrenheit) and mild winters (lows of mid 30 degrees Fahrenheit). Annual precipitation is highly variable, with long periods of drought and above normal precipitation. Population is estimated at about 39,230 for 2000. The watershed is predominately agricultural on the valley floor. Approximately 2.2 million pounds active ingredient of pesticides and an estimated 17.6 million pounds active ingredient of nitrogen and phosphorus fertilizer is applied annually to the agricultural land.

CONTENTS

Abstract

Introduction

Description of the Lower Merced River Basin

Physical and Cultural Features

Physiography

Geology

Soils

General Land Use

Agricultural Land Use

Pesticide Use

Fertilizer Use

Urban Land Use

Climate

Hydrology

Water Availability

Surface Water

Ground Water

Summary

References Cited


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