Geoscience Reference
In-Depth Information
Table 26.2
20-year history of flow experiments from the Glen Canyon Dam, 1990-2010.
Flow treatment
Duration
Objective(s)
Replication
Monitoring
Varied patterns of
daily power-plant
releases (to inform
environmental
impact statement
studies).
10-day periods with
4-day monitoring
(14 months in
1990-1991).
Sandbars, fish
conservation, river
navigation, sand
transport, water
temperature,
modelling support.
Daily release patterns
were repeated over
10-day cycles for a
given flow scenario,
then flows were
lowered and
stabilized while
sandbar monitoring
occurred.
Discharge, stage,
temperature and
suspended-sediment
transport, fish and
other aquatic
parameters,
including synoptic
quality of water.
Interim daily
fluctuating flows
(experimental
re-operation of dam
under low
fluctuating flows
(LFF)).
August 1991 to
October 1996.
Conserve sandbars,
fish, improve river
navigation, limit
sand transport.
Diurnal flows were
limited, and were
varied with annual
hydrology.
Discharge, stage,
temperature and
suspended-sediment
transport, fish and
aquatic food.
1996 record of
decision (ROD) -
rules governing
daily fluctuations
(interim LFF rules
are changed to
modified low
fluctuating flow
operations).
Ongoing since autumn
1996 with only
occasional
interruptions to
conduct other
related flow
experiments, such as
high flow and low,
steady flow tests.
Sandbars, campsites,
aquatic food, fish,
archaeological sites.
Yes; annually with
variation derived
from upper
Colorado River Basin
hydrology.
Discharge, stage,
temperature,
suspended-sediment
flux, fish, aquatic
food, campsites,
archaeological sites.
Beach/habitat-
building flows
(or high-flow
experiments).
Spring 1996 and 2008;
autumn 2004.
Sandbars and related
near-shore habitats.
Yes, both sand
depleted and
enriched conditions
with peak flows of
2.5 to 7 days.
Sandbars and sand
mass balance, sand
grain size, native
(humpback chub)
and non-native fish
(trout), cultural
sites, campsites,
food production,
riparian plants,
power revenue.
Habitat maintenance
flows.
Autumn 1997, spring
and summer 2000.
Sandbars and native
fish, including
humpback chub.
Yes, under both sand
depleted and
enriched supply
conditions.
Sandbars and related
near-shore habitats,
fish and food, plus
riparian plants.
Spring and summer
steady flows.
April-September 2000. Humpback chub.
No.
Native fish abundance.
Autumn steady flows.
2008-2012.
Humpback chub.
Yes - annually during
September-October
over 5 years.
Near-shore juvenile
chub habitat use
and survival.
Enhanced winter
fluctuating flows.
2003-2005.
Limit rainbow trout
recruitment through
increased juvenile
mortality rates from
flows.
No - one 3-year block,
increased winter
fluctuations in
January through
March.
Rainbow trout
abundance in
tail-water reach
below dam.
