9581

• UCREFRP Catalog Number: 9581
• Author: U.S. Bureau of Reclamation.
• Title: Final Environmental Impact Statement - Navajo Reservoir Operations Volume II Technical Appendices.
• USFW Year: 2006.
• USFW - Doc Type: Grand Junction - Durango, CO.
• Copyright Material: NO

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Appendix C
Hydrologic Modeling Analysis

Introduction.

This appendix details the analysis process for determining impacts to hydrology from
operation of the No Action Alternative, the 250/5000 Alternative (Preferred Alternative),
and the 500/5000 Alternative. The results of this modeling effort are also presented.

Understanding the impact of the alternatives on the water resources of the San Juan River
basin requires modeling the complex relationships associated with multiple diversion and
return flow points in the basin. A number of basin-scale models exist that take hydrologic
input data and simulate the behavior of various processes under different sets of water
allocation and infrastructure management. A distinguishing feature of these simulation
models is their ability to assess water resource system responses over the long term.

There are several best-science river basin simulation models available, anyone of which
would be appropriate for developing and analyzing San Juan River flow recommendations.
RiverWare was selected primarily because of its flexibility and capability to simulate all key
features within the San Juan River Basin. RiverWare has been implemented in the San Juan
Basin since 1998 in support of assessing the relationship between flow recommendations for
endangered fish in the San Juan River and water development. This implementation has
been completed by the U.S. Bureau of Reclamation (Reclamation) and Keller-Bliesner
Engineering as a consultant for the U.S. Bureau of Indian Affairs (BIA). The application for
this analysis is an extension of that work.

Modeling Approach

RiverWare.-RiverWare is a generic hydrologic modeling tool using an object-
oriented design and a graphical user interface (Gill) to allow users to develop data-driven
and variable time-step models for both planning and operational uses. Because of its
flexible and extensible design, it can be readily customized to fit specialized modeling needs
for any river system. One of the features of RiverWare is its ability to solve a river basin
network (developed by the user with the graphical user interface) with different controllers
or solution techniques. Currently, there are three different controllers: simulation, rule-
based simulation, and optimization. A fourth controller for water ownership and
accounting is currently being developed. RiverWare has been in development since 1993
and is the result of a continuing collaborative effort between the Center for Advanced
Decision Support for Water and Environmental Systems at the University of Colorado,
Reclamation, and the Tennessee Valley Authority (TV A).

A model of a river system network is constructed by placing objects from a palette onto a
work space using the Gill. Objects in RiverWare represent the features of a river basin. The
objects supported by RiverWare are storage reservoirs, power reservoirs, pumped storage
reservoirs, river reaches, aggregate river reaches, confluences, aggregate diversions for

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