(GP/GT) for Additional Water Supply in the Lower Rio Grande

February 19, 1990
MEMO
• "J :
7?O!1 :
SiJ3JECT:
Interested TAA Members
Kevin Rafferty, Geo-Heat Center
Heating Requirements for Thermal Refuge Areas
Following this year's Texas Aquaculture Association meeting and
field trip, I had the opportunity to meet with several of the
commercial growers and tour their facilities (including: Redfish
~nlimited, Sout~west Mariculture and Sealantic Inc.). Much of t~e
discussion on the field trip and in subsequent meetings focused on
the issue "thermal refuges" to shelter t~e fish during extreme
winter conditions.
The design for a refuge which seemed acceptable for most operators
involves an arrangement modeled after that used successfully by
Richie Farms this winter. In this case a cover was suspended by
cables over a corner of the pond forming a triangular sheltered
area. The cover was installed approximately level with the pond
banks (only a foot or two off the water). On the side facing the
pond, the cover was extended underwater and weighted in order to
form a wall between the refuge and the open pond. A space was left
between the cover and the bottom of the pond for fish passage.
Richie Farms had the advantage of using an 86°F well to provide
heat for their thermal shelter. For most other operators, some
other source (boilers, etc.) would be required to provide the heat
input. The enclosed curves were developed to assist in heater
sizing.
Three curves are provided, one each for 50°, 60° and 70 0 p pond
water. This temperature refers to the value which would apply to
the wate:::- under the cover. Three types of- lines appear on each
graph. The lines sloping' from "lower left to upper right correspond
to outside air temperature and represent the heat loss through the
cover (from the air under the cover to the outside air). The lower
curve, sloping from the upper left to the lower right represents
the heat gain from the pond surface to the air under the ~over.
The upper curve sloping from upper left to lower right is a plot
of the required heat input to the water. To use the graphs, first
select the graph associated with the minimum temperature which you
·.... ish to maintain in t.1j,e refuge (50°, 60° or 70°F). Using the
minimum outside temperature Which you feel appropriate to your
location, find the intersection between the curve for that
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