A Conceptual Model for Floodplains in the Sacramento–San Joaquin Delta

Jeffrey J. Opperman

doi:10.15447/sfews.2012v10iss3art4

Abstract

Floodplains are among the most biologically productive and diverse ecosystems on Earth and they provide significant benefits to society such as attenuation of floodwaters, groundwater recharge, filtration of nutrients and sediments, carbon sequestration, fisheries productivity and recreation. However, floodplains are also among the most converted and threatened ecosystems. Floodplain habitats in the Sacramento-San Joaquin Delta, and throughout California’s Central Valley, have been greatly reduced from their historic extent and key processes that create and maintain floodplains, such as flood flows and meander migration, have been greatly altered. These widespread alterations to habitats and processes have lead to declines in many species’ populations in California’s Central Valley and Delta, creating challenges for both environmental and water management. To address these challenges numerous entities and programs are now focused on restoring floodplains and other Delta habitats. This paper provides a conceptual model for floodplains that characterizes the key features and identifies the critical processes, drivers, and linkages that allow floodplains to produce a variety of functional outputs of management importance. These outputs include: (1) the floodplain habitat mosaic, including riparian vegetation and its associated wildlife; (2) spawning and rearing habitat for native fish; and (3) food-web productivity that can support native fish on the floodplain as well as be exported to downstream ecosystems. The model emphasizes that the production of these outputs from floodplains requires vertical and lateral hydrological connectivity across a broad range of flow conditions. For example, long-duration flooding in the spring promotes native fish spawning and food-web productivity that benefits native species.

Highlights

The Sacramento–San Joaquin Delta, within California’s Central Valley (Figure 1), encompasses a broad suite of habitat types including open water, tidal marsh, agricultural fields, and river-floodplain ecosystems (TBI 1998)
Because of the Delta’s importance for agriculture and as the hub of the California water system, reversing this decline poses a considerable challenge for natural resource managers
I focus on the key processes and features required to maintain a set of outputs from floodplains that have management significance, including native fish populations, biologically available carbon and other aquatic food resources, and riparian vegetation and riparian-associated fauna

Summary

Introduction

The Sacramento–San Joaquin Delta, within California’s Central Valley (Figure 1), encompasses a broad suite of habitat types including open water, tidal marsh, agricultural fields, and river-floodplain ecosystems (TBI 1998). These characteristics structure the biotic and abiotic environment for several important “outputs” that depend on inundated habitat, such as Sacramento splittail (Pogonichthys macrolepidotus), juvenile Chinook salmon, and the production of phytoplankton (Model 3).

Objectives

Results

Conclusion