WSP09548

• File Number: 8240.200.17.F
• Description: UCRBRIP Hydrology Sub-Committee
• State: CO
• Basin: Colorado Mainstem
• Date: 1/1/1985
• Author: CWCB
• Title: Critical Assessment of PHABSIM Model
• Water Supply Pro - Doc Type: Publication

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REPORT OF THE BIOTECHNICAL SUBCOMI'IITTEE

Introduction and Overview

The Biotechnical Subcommittee. and interagency working group, Nas organized in
May 1984. Its task Nas to determine the habitat requirements of the endangered
Colorado River fishes--those habitat characteristics that are essential to the
survival of these species. During the past several months, the subcommittee
has been cooperating with the Fish and Wildlife Service in the development of a
complex computer model of the habitat of the Upper Colorado River Basin
endangered fishes. The model consists of several components--actually
individual models that are interfaced with one another and thereby function to
predict the availability of habitat for endangered Colorado River fishes under
past. present. and possible future conditions of water development in the
basin. Component models Include a hydraulic model (HYDROSSl that predicts
discharge conditions under various potential water-development scenarios, a
temperature model that predicts river temperatures under these scenarios, and a
physical habitat simulation model (PHABSIMl that uses outputs from the previous
models to predict the availability of habitat for endangered fishes. The
predictive ability o~ the habitat simulation model Is there~ore directly
related to the predictive ability (accuracy) of the hydrology and temperature
models.

In January 1985 the Biotechnical Committee was given the responsibility of
critically analyzing the PHABSIN model relative to the model's ability to
predict flow-related changes In habitat for the endangered Colorado River
fishes. The specific objectives of this analysis. as established by the
committee. were as follows: 1> to identify the "data gaps" (major
deficienciesl evident in the modeling effortl 2) to identify approaches to
testing/validating the modell 31 to Identify data/research needs; 41 short-term
implementation of ESA Section1~ 3) long-term implementation of ESA Sectlon7~ _n,}
6) Conservation funding; and 71 future Biological SUb-committee activities~ I~~
This document describes the results of that analysis. ~u.>r,."A, ;:'0
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Major Deficiencies J-4~ J-IAR...~HIP-'
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ADDITIONAL CONCERN 5. The interagency effort has resulted in the development
of a flow/habitat modell however. there are other important environmental
parameters that--a1though not flow-related (e.g., contaminants. competitive
spp.. movement barriersl--might have important effects on endangered fishes.
These factors must be included or assessed if they are found to be important to
the maintenance and development of populations of endangered fishes.

RECOI'IMENDATION: Testing/validation of the modet" re9uires testing of the
following hypothesis: Nonflow-related characteristics of the environmen~ have
Important effects on the populations of endangered Colorado River fishes.

RECOMMENDATION: Data/research needed to test the above hypothesiS include the
following:

1