Michigan Department
of Natural Resources
Fisheries Research Report No. 2047, 1997
ASSESSMENT OF MANAGEMENT
ALTERNATIVES FOR ALTERING
THE THERMAL REGIME OF THE BETSIE RIVER, MICHIGAN
Tammy
J. Newcomb
and
Thomas G. Coon
Abstract.-The
Betsie River in northern Michigan is classified as a marginal trout stream
because in some reaches, instream summer temperatures exceed the tolerance
limits for trout species. In 1989, Thompsonville Dam failed, which resulted
in an additional 15 km of stream available to migratory steelhead Oncorhynchus
mykiss adults and juveniles. However, water temperatures in the upper
watershed may still limit the production and distribution of these fish.
The objectives of this study were to: 1) describe the current thermal
regime throughout the Betsie River watershed and characterize it in relation
to juvenile steelhead life history requirements, 2) evaluate empirical
water temperature models based on air temperature to predict instream
temperatures throughout the watershed, and 3) develop a physical process
temperature model to evaluate the thermal effects of removing a remaining
low-head dam in the headwaters or, alternatively, the addition of cold
water from the hypolimnion of the source lake. Under current channel conditions,
summer temperatures in the upper Betsie River routinely exceed the optimal
growth limits for steelhead and sometimes the upper incipient lethal level,
with mean summer temperatures from 21-23°C and maximum temperatures up
to 28°C. Although, instream water temperatures were strongly correlated
with air temperatures (r2 = 0.81 to 0.92), air temperature
was a poor predictor of winter water temperatures. The physical process
model predicted instream summer temperatures reasonably well and provided
for simulation of management alternatives. Removal of Grass Lake Dam would
likely result in mean daily summer water temperatures 2°C lower than under
current conditions in both typical-flow and low-flow water years for the
reach from Green Lake to Grass Lake. In the Grass Lake to Thompsonville
reach, mean daily water temperatures were predicted to be less than 1°C
lower than under current conditions in a typical and low-flow year. The
addition of hypolimnetic water would result in temperatures 4°C lower
than under current conditions in the Grass Lake to Thompsonville reach.
Although these management alternatives may provide better thermal habitat
for juvenile steelhead during the summer in this 15 km reach of river,
the trade-offs, including the loss of wetland habitat and fishery and
recreational boating opportunities in the current impoundment, should
be considered.
Fisheries Research Report No. 2047 
- Full Text Acrobat Reader File.
