Pond Boss Forums GENERAL QUESTIONS Help Keeping water temp cooler in summer

is there anything man made that can be done to shade or keep pond cooler in the summer? i have spring fed gravel bottom pond. 2 acres. spring water temp is 52 degrees, surface temp is upper 70's. average dept is 6 ft maybe 7 at depest.

If surface temp is upper 70's, what is your goal in cooling it down? What species do you have or other reasons for the cool-down?

Sounds like a trout pond?

If spring-fed, does your outlet pipe run all summer? If so, you should set up your pipe to draw from the surface, or just below, to pass the warmest water through the outlet.

Another option would be to deepen the pond. More thermal mass leads to lower summer temperatures, just based on the lag in warming the average temperature of the pond.

Another option would be some floating islands of water plants. That should provide some shade, perhaps a little cooling from transpiration, and the plants will take up some of the nutrients that might otherwise go to algae growth. Further, the dangling roots would be a new micro-environment for zooplankton and some of your forage fish.

The search function should turn up some of the past threads on floating islands.

Also, you could build a dock from land, or a floating dock for swimmers if either of those was in your long-term plans. That would provide a tiny amount of shade in the pond.

Finally, do you have AC electricity at the pond? There are some aerial water sprayers for aeration of the water, but they are mostly decorative. (It is much more efficient to use bubble aeration in the water column to add oxygen to your pond water.) I would assume that type of sprayer creates some evaporative cooling in the atmosphere above your pond. (Which would cool the air ABOVE your pond, but would IMHO have very little effect on your water temps.) Perhaps if you turned that type of sprayer sideways (or created your own sprayer) and directed it at the pond surface, then you might get the evaporative cooling to occur right at the surface of the pond. (However, I think this would not give you much cooling for the cost and effort.)

If you are trying to make the pond more amenable for the survival of trout, I believe most of our trout people on Pond Boss do add a little water column aeration in their ponds. Slightly warmer water with more oxygen is better for trout that would otherwise be struggling in the low dissolved oxygen conditions that come with the warmer water temperatures of summer.

Good luck with your pond! I hope some of my wild ideas trigger a few good thoughts on your end that might actually apply to your conditions.

“Surface temp in the mid 70’s”. Those of us in Texas can only dream of that. We will hit 107 or somewhere around that today. Been that way for awhile and not much relief in sight.

They DO make large chillers to cool indoor aquariums. Think of Sea World scale chillers.

Adding trout to the pond this fall. Hoping they Would live through the Summer. I have a lot of shade trees but just seeing if there are any other options. Pond is set up as a bass/bg/perch pond right now. With it being spring fed I thought it be cool to get a couple dozen brown trout in there.

Water does drain all year. Drains from top of the water column. I did damn it up and raised the water about another foot I have 5 docks on pond already. Once it freezes over I might rent a big backhoe and dig out a couple spots 12-15 feet deep.

I am NOT a trout guy, but I don't believe they die from the heat directly, but rather because warm water holds much less dissolved oxygen than the cold water they are adapted for.

I agree that having a spring-fed pond with an outlet drain that passes surface water gives you a chance of keeping trout throughout the summer. (Which state is your "Cambridge"?)

Your key to trout survival will be to provide them with cooler, more oxygenated water. Maximizing those two factors is difficult because boosting one factor usually hurts the other factor.

I will address the water temperatures first, since those thermodynamic rules are less "pond dependent".

A temperature stratified pond in the summer will have a lower AVERAGE temperature, AND cooler water in the deeper portions. I think trying to achieve a cooler average temperature for the pond should be one of your goals to support your trout. Almost 100% of your heat loss from the pond comes from the surface of the pond. RADIATIVE heat loss is a temperature dependent function. The higher the water temperature at the surface, the more radiative heat losses that will occur from the pond at night. Basically a pond that is 80F at the surface and 60F at the bottom will radiate away more heat than a pond that is 70F throughout the water column. After a few weeks of summer, the stratified pond will start to exhibit a lower average temperature.

The other important means of heat loss is evaporative cooling. This process is also temperature dependent. The stratified pond with warmer surface water will also have more evaporative cooling during the night than the perfectly mixed pond with uniform temperature. The stratified pond will even have more evaporative heat losses during the day - even if the pond is still increasing in temperature due to solar insolation and heat transfer due to warmer air above the pond.

Unfortunately, here comes the complicated part: a well stratified pond will tend to have less oxygen in the cooler water where the trout are residing! A perfectly aerated pond will tend to be well-mixed and have a more uniform temperature throughout.

So the correct answer is to get an aeration system working in your pond in such a way that the pond can still lose as much heat as possible overnight. That is a VERY pond specific condition to create with your aeration system.

There are several aeration experts on the forum, that may be able to help you with that problem. (And it is a very complicated problem.)

I can only really help on the temperature side (which is only half of the problem). Do you live at the pond? If so, then one option may be to let out water episodically rather than continuously. Perhaps turn off your outlet for 2-3 days, and then go drain 3-6" of the hottest water off of the surface starting at 5PM when you get to the pond after work?

Another option is to dig some deeper areas as you suggested. This is an expensive option, and is not a perfect solution. When your pond does stratify in the summer, the cold deep pools will become anoxic and trout will NOT reside in that water. (I believe some of the aeration guys do use the cooler water as a heat buffer. They put their aerators a few feet off the bottom of the deepest pools, or put the aerators adjacent to the deepest pools but at a somewhat shallower depth.)

Right now, it might be a good idea for you to start collecting some valuable data. Does one of your docks reach out into deeper water? If so, you might start recording temperatures for your surface waters and your waters at depth. That information throughout the year will definitely help you revise your aeration plan as needed.

The other item is to purchase a dissolved oxygen meter. I believe every single trout person on the forum that has warmer water ponds either owns an expensive oxygen meter, or a VERY expensive oxygen meter. If you are going to be spending a lot of money on pond alterations and on stocking trout, you may need to bite the bullet on that expense.


P.S. I just went back to the top and re-read your original post. If you have enough 52F spring water entering the pond, then your trout may be able to survive some upper 70s surface water temperatures. Water from springs is typically very oxygen deficient! Maybe some mild aeration columns will be enough to get your trout through the summer? (My comments above about stratification and water temperatures did NOT include the scenario with a supply of 52F water continuously entering the pond.)

Experimentation is also a valuable tool. Are your two dozen brown trout the minimum order? That number of trout should have no problems (area wise) in a 2-acre pond. Put them in this fall, and then monitor your temps closely next summer. If they don't make it through, then you can consider what more expensive options (deepening, aeration, etc.) that you need to perform to have a sustainable trout population.

Good luck!

As Fishinrod suggests covering some of the pond's surface would help...it is easy however costly but one could purchase closed-cell styrofoam [1.5 inch thick] in 4feet by 8feet size and as floating pads along the shoreline, or join them into wide islands roped to the bottom with concrete blocks...currently cost of these sheets ranges in the $30--40 each range. The foam insulates very effectively, lasts for many years exposed to sunlight and the bottom side will grow algae and all manner of water creatures.

I currently have a few sheets that float around the pond during the summer...in the fall these 'islands' are pushed under the pontoon dock to protect the aluminum pods from ice -- also run the aerator next to the dock pontoon which prevents the open pond from crushing the pods...and this also adds oxygen to the pond water during the ice snow cover during January/February...you could move your island pads under your docks or around the docks in winter too.

There may well be many solutions to help lower your summer water that require energy -- geothermal comes to mind -- a closed loop water lines heat treatment system -- from surrounding cold ground temperatures to be heat sinks for pond water -- electric pumps moving thousands of gallons of water hourly during the warmer summer days -- if one can keep the temperature withing trout range for 60-90 days -- maybe one stocks trout every fall, enjoys fishing catching eating as many as possible until summer water temperatures are too high...size and number limited but catch and eat enjoyment would still exist.

Or just make sure that the O2 levels are at saturation. A customer had trout still alive at 80°F. But the mg/l was in the upper 9's. Bottom diffusion aeration system plus a volcano type agitator. Golden Rainbow trout is what they were.

How big is the pond? What is the average water clarity in feet during all mid summer? Less depth equals less water volume which means the dissolved oxygen does not last as long especially in mid summer and winter when it is important to have maximum amount of dissolved oxygen for trout. .
Your shade trees will deposit a lot of leaves into the pond. Leaves lying on the bottom decomposing consume lots of dissolved oxygen which is needed by the trout. This is not a good thing especially in mid summer when trout usually struggle to find cool well oxygenated water. Lots of decaying leaves decomposing are not a good thing when trying to maintain trout during July and August.