9617

• UCREFRP Catalog Number: 9617
• Author: Scott, M. L., M. A. Wondzell and G. T. Auble
• Title: Hydrograph Characteristics Relevant to the Establishment and Growth of Western Riparian Vegetation
• USFW Year: 1993
• USFW - Doc Type: Hydrology Days Publications
• Copyright Material: NO

INTRODUCTION

Riparian zones or bottomlands are water courses and
associated areas of alluvial sediments. In arid and
semi-arid regions of North America, riparian
woodlands bordering streams and rivers are
distinctive features representing topographic
positions that are consistently moist enough to
support the growth of trees in a .landscape that is
otherwise too dry. Riparian zones represent important
transitional areas between upland and aquatic
ecosystems (Gregory et ale 19~1) and provide
essential habitat for a wide diversity of vertebrate
species (Brinson et ale 1981, Knopf 1985).

Western riparian ecosystems, particularly at lower
elevations, are often dominated by~species of po~lar
and willow. These early successional speC1es,
including plains cottonwood (Populus deltoides subsp.
monilifera (Aiton) Eckenwalder) 'are adapted to
relatively frequent, intense disturbances produced by
the energy of flowing water in riparian environments
(Osterkamp and Costa 1987). streamflow in most large
western rivers and streams is now influenced br
management activities including agricultura
diversion and damming for power generation and flood
control. Such activities have; caused dramatic
changes in the diversity, structure~ and organization
of riparian vegetation throughout western North
America. Changes in the magnitu~e and timing of
flows have led to marked declineslin the extent of
riparian vegetation in some river systems (Johnson et
ale 1976, Fenner et ale 1984, Rood.and Mahoney 1990).
However, in situations where natural flow
fluctuations historically prevented establishment of
vegetation, the moderating e.ffects of water
development have led to at least tem~orary increases
in the extent of riparian vegetat10n (Nadler and
Schumm 1981, Williams and Wolman 1984).

Ha,nagement of riparian resources within a larger
framework of water management will require clear
articulation of flow characteristics relevant to
riparian vegetation. In this paper we discuss stream
hydrograph characteristics critical to conditions
required for establishment, growth, and survival of
native riparian vegetation.

ECOLOGICAL REQUIREMENTS

The capacity of moving water to erode, transport, and
deposit alluvial materials is central to the
structuring and maintenance of western riparian
ecosystems (Brinson et ale 1981). Early successional
species, like many riparian willows and poplars,
possess a number of ecological characteristics that
make them particularly well-suited to physical
conditions in riparian zones. We discuss the
ecological requirements for germination,
establishment, growth, and long-term survival of
riparian vegetation, using plains cottonwood as an
example.

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