USGS

Carbon Fluxes, Water Levels, and Related Environmental Data, Twitchell Island, Sacramento-San Joaquin Delta, California, November 1992 through September 1995

By Barry D. Kerr, Bronwen Wang, and Judy Z. Drexler

 

U.S. GEOLOGICAL SURVEY

Open–File Report 03-370

Sacramento, California 2003


Prepared in cooperation with the
California Department of Water Resources


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Abstract

    Most of the Sacramento-San Joaquin Delta was leveed, drained, and converted to agricultural use by the 1930s. Land-surface elevations have since subsided by more than 20 feet in some areas. Subsidence increases the likelihood of levee failure and flooding, which, in turn, jeopardizes water delivery and water quality in the Delta. This is of major concern because the Delta supplies water to two-thirds of California. Previous research has shown that oxidation of peat soils is the primary cause of subsidence in the Delta. Therefore, a possible strategy for remedying this situation is to convert drained agricultural fields back to wetlands, which are flooded at least part of the year. Rehabilitation of wetlands would promote the growth of peat, thereby mitigating and possibly reversing subsidence.

    This report describes a study that evaluated this strategy. In three experimental enclosures or ponds, carbon inputs were measured in the form of plant biomass and outputs in the form of carbon dioxide (CO2) and methane (CH4) fluxes. Each of the ponds received one of the following water treatments: seasonally flooded, seasonally flooded and irrigated, or permanently flooded. Land-surface elevation, ground-water levels, and soil and air temperature also were measured. This report presents the data collected during the initial phase of the study, which ran from November 1992 through September 1995.

CONTENTS

Abstract

Introduction

Description of Wetland Enclosures

Methods and Data

Soil Moisture

Soil Percent-Carbon Content and Bulk Density

Ground-Water Levels

Elevation Measurements

Gaseous Carbon-Flux Measurements

Biomass Measurements

Summary

References Cited

Tables


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