8283

• UCREFRP Catalog Number: 8283
• Author: Silk, N., J. McDonald and R. Wigington.
• Title: Turning Instream Flow Water Rights Upside Down.
• USFW Year: n.d.
• USFW - Doc Type: Boulder, CO\
• Copyright Material: YES

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Conventional
Constant Instream
Flow Water Right

o

Oct Nav Dee Jan Feb Mar Apr May Jun Jul Aug Sep
Time
FIGURE 1. Conventional Constant Instream Flow Water Right

Although such an instream flow water right might protect one life stage or habitat
component of a targeted riverine species, it would hardly protect the variable and
complex flow regime of an entire river ecosystem. The question of how much flow
should be protected for a river ecosystem has many more dimensions. Due to the
hydrologic variation that defines the ecological niche of each species in such an
ecosystem, we must also ask: What is the timing and magnitude of each flow level? How
long does the flow level need to be maintained? How fast or slow should the rate of
change be from the former and to the next flow level? Even if we could answer these
questions for an individual fish or invertebrate species, to protect the full complement of
native biodiversity living in a particular river we would have to answer these questions
for all species in each river.

A small step toward expressing 'such flow variation in an instream flow right is to
specify its amount by season or months. In Arizona, the amounts permitted for the
appropriation of instream flow water rights for wildlife and recreational purposes have
been based on median monthly flows. Such a step toward expressing hydrologic
variation in an instream flow right converts one statistical value for that variation into a
constant amount for any month and produces a stair-stepped flow quantification (Figure
2).

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