Natural Pond

[Hygge]

Hi
I wonder if anybody would be kind enough to offer some help please? We bought a house 2 years ago with a large, natural, flowing pond. I should make it clear that we know nothing about ponds at all! I am therefore giving any and all information that may be of use to those of you who do and apologise for this being a long post.
So, by 'flowing', I mean that water comes into the pond at one end through the ground and a couple of pipes that run under our garden from the surrounding agricultural land, see below:

and leaves at the opposite end via a kind of weir before going through various underground pipes until it reaches a ditch which flows into the local river just down the road.

As you can hopefully see from the photo below, the pond has a large willow tree on either side of it.

By 'natural' I mean the pond has been here a very long time (pre-1860 when the house was built) so there is no liner etc (this may not technically be the definition of a natural pond so I hope this clarifies it!) There are no fish at all in the pond but it does contain large numbers of pond snails and frogs. At the deepest point the water is around 3ft deep and is much shallower at the edges. There is a large depth of silt in the bottom - maybe a 12 inches or so in the deepest part.
The first year we were here (2016) we had green algae form on the surface which I removed with a garden fork. The second year (2017) the algae returned along with something that looked like a type of grass. At this point, following some avid googling which told me not to remove the algae, I immersed a bale of barley straw in the pond near to the water inlet side (sorry, I can hear you all groaning following reading some of the posts on here but I didn't know any better at the time) After a month or so the algae died back and turned from a bright green colour to a pale gold, at which point I removed the dead remains along with the 'grass' which was very easy to just pull out.
After reading that the algae was feeding on excess nutrients I tried adding a few water lilies to the pond, these have thrived and have formed 3 quite large clumps (one of which can be seen in the second photo)
This year the algae is back but it is interspersed with another type of week/plant which is growing pretty ferociously and lots of duck weed (but no grass this year?!!) I pulled some of the new plant/weed out the other day, see below:

I have no idea if this is a good or bad plant/weed but there is probably as much of this as there is the algae now. See below a small area:

My assumption so far, based on what I have read on the internet, is that the algae is probably a result of a combination of factors that are resulting in a perfect storm:
1. The water coming in from the arable land could be high in nutrients due to sprays etc
2. The pond gets very little sunlight due to the over-hanging willow trees
3. There is nothing in the pond to remove the nutrients
But I don't know what I am talking about so would really appreciate any help! I guess my main questions are:
# What can I do to eliminate the algae issue?
# Is the new plant/weed good or bad? So should I leave it or remove it?
# Will adding more water lilies help? Or any other plants?
# Is there anything else I can add? Obviously the water flows into the local river so it needs to be environmentally sound.

Apologies again for the long post and many thanks in advance if anyone is able to throw some ideas my way or correct my current assumptions.
Kindest regards
Kerry

 

[carolinaguy]

Great post. You have a eutrified pond on your hands due to an excessive amount of fertilizer runoff and other nutrients. In the United States we have what are called county agents who work for state agricultural departments or are contracted and work from university staffs. In our state, Clemson University fulfills some of that role and has a website, www.hgic.edu I think. They have a huge library of pond management information that they share. Of course their information is South Carolina climate based, but the stuff is still good.

A eutrified pond will kill off all fauna — snails, worms, clams, fish, everything by depleting all oxygen at night. My first blush reaction is to pull out as much vegetation as you can and compost it. The surface needs to be cleared I think. You probably need to have the water and soil tested. Clemson does this for six dollars US. I assume there is an organization available to you that will do something similarly. Then you can react based on their conclusion.

 

[sissy]

I had one in the other house I bought but it had a liner and was fed by Frying pan creek . Not sure what the other owners did and why as the house had been empty for over 4 years on 12 acres .Took a month of cleaning it and decreasing the size .But mine was not that bad and they can become a mosquito breeding ground .They have the same problem with the Chesapeake Bay .cow poo and fertilizers washing into it .

 

[Jhn]

The shade over the pond is helping with the algae.

You do have nutrient consumers the lilies and the pondweed are consuming nutrients just not enough.

Agree, on clearing the surface of the pond.

There are a couple ways to attack it.

One, where the feed pipe comes into the pond, how far away does it go, where does it start?

I ask because I would unearth the pipe a good distance back from the pond, cut it, and create a wetlands/bog filter the water would need to run through to get to the pond. The idea is the plants in this filter get to the nutrient rich water before it gets to the pond. Depending on slope, you could incorporate step pools, as well to allow sediment to settle out before it gets to the pond. You could use a liner, bentonite or depending on if it is a natural spring feeding through the pipe could probably do it w/o either just using filter cloth, sand, gravel and various size stone/ cobble, but w/o knowing soil in the area you are located it is hard to say.

Secondly, you could add circulation to the pond once you clean it out, through an aerator.

Lastly, cleaning out the pond once surface is cleaned. If there is alot of silt in the pond, you could use a gas powered trash pump to pull/suction the silt out of the pond, if you had a place to silt fence off creating a pen then pump it into that area. Of course, this would empty the pond of water, but if it has a steady flow of water feeding into it no big deal.

 

[Hygge]

Thank you for all your great responses! I will happily clear the surface of the pond as it looks such a mess. I was only leaving it as I wasn't sure if I was doing more harm than good! Should I clear this stuff out too?

I wasn't sure if it was a kind of oxygenating plant that may help?
Thanks again for your thoughts, I will have a good read of these properly over the weekend and get a plan in place.

 

[Lisak1]

I don't know what that plant is, but it sure is pretty! Does it grow completely underwater? Is it coming from the bottom?

 

[bagsmom]

Is it hornwort?

 

[bagsmom]

The shade over the pond is helping with the algae.

You do have nutrient consumers the lilies and the pondweed are consuming nutrients just not enough.

Agree, on clearing the surface of the pond.

There are a couple ways to attack it.

One, where the feed pipe comes into the pond, how far away does it go, where does it start?

I ask because I would unearth the pipe a good distance back from the pond, cut it, and create a wetlands/bog filter the water would need to run through to get to the pond. The idea is the plants in this filter get to the nutrient rich water before it gets to the pond. Depending on slope, you could incorporate step pools, as well to allow sediment to settle out before it gets to the pond. You could use a liner, bentonite or depending on if it is a natural spring feeding through the pipe could probably do it w/o either just using filter cloth, sand, gravel and various size stone/ cobble, but w/o knowing soil in the area you are located it is hard to say.


I love the idea of cutting back the drainage pipe and having it flow through a bog filter!

I don't know why my comments always get incorporated into the quote -- but I'll say it again -- cutting back the drainage pipe and having it flow into a bog for filtration is a great idea!

 

[carolinaguy]

Do not look at plants as oxygen producers. That they produce oxygen through the photosynthesis process as a byproduct is misleading. The real biological process is the consumption at night by plants of oxygen in the absence of light. The plants suck out every ounce of oxygen from the water that they can absorb and drop the oxygen level below survival, it’s like elevating the pond to 35000 feet where there is so little oxygen that we humans die in about 90 seconds. That analogy is flawed by the change in atmospheric pressure yes, but the idea is that there is not enough oxygen to sustain life. Every oxygen breathing animal in a eutrified pond suffocates at night. It’s an episode of the plant walking dead in eutrification. Get rid of the zombie plants.

 

[Tara]

If the pond is natural, do you have to use the flow from the pipes to top off the water. If you do are you sure the water is not just a shared (underground water source), this was done before more water mains were made available. If it is agricultural run off, I'm surprised it's allowed drain into the river. Maybe test the water, it could be just a neglected pond. If you don't want fish maybe add a water feature, and circulate some water. Clean it and get a pump and make a waterfall. There is a lot of options. If the law permits it, and you build a bog you could have beautiful plants there. Best of luck, and let us know how it goes.

 

[Hygge]

Is it hornwort?

That's what I was thinking. It just floats around, doesn't seem to have any roots in the bottom of the pond.

 

[Hygge]

I don't know what that plant is, but it sure is pretty! Does it grow completely underwater? Is it coming from the bottom?

No roots, not coming from the bottom. It just floats around!

 

[Tara]

Just had a thought about your pond. If it's there a long time perhaps you have a blockage somewhere in the inflow pipe. The reason I'm asking is because back in the day, farmers were just about geniuses in getting water onto their land. Your pond may have been set up initially as a constant flow of fresh water coming in and out continuously to feed animals. The constant non stop flow kept the water becoming stagnant. May check the old land records.

 

[bagsmom]

Great post. You have a eutrified pond on your hands due to an excessive amount of fertilizer runoff and other nutrients. In the United States we have what are called county agents who work for state agricultural departments or are contracted and work from university staffs. In our state, Clemson University fulfills some of that role and has a website, www.hgic.edu I think. They have a huge library of pond management information that they share. Of course their information is South Carolina climate based, but the stuff is still good.

A eutrified pond will kill off all fauna — snails, worms, clams, fish, everything by depleting all oxygen at night. My first blush reaction is to pull out as much vegetation as you can and compost it. The surface needs to be cleared I think. You probably need to have the water and soil tested. Clemson does this for six dollars US. I assume there is an organization available to you that will do something similarly. Then you can react based on their conclusion.

I was thinking about your description of a eutrified pond. I wonder if this is occurring in my lotus pool and in my container water garden. In still water, can the condition be corrected by removing a lot of the plants but leaving some? I have many plants in the lotus pool, especially. The water is clear and beautiful -- but I've wondered why no frogs used it to lay eggs in. Maybe they did, but nothing survived?

 

[carolinaguy]

Maybe. The keys to eutrification are that the surface tends to be totally covered with vegetation so that there cannot be enough oxygen exchange between the water and the atmosphere to keep up with demand in the water and there is no flow through the pool from an outside source . The pool may be 20 feet deep but it will be clear and lifeless to the bottom. The cause is excessive nutrients in the water. If your pool has some evidence of life in the form of invertebrates under water then it’s not completely devoid of oxygen, but it may be so depleted that at night oxygen saturation is too low to support tadpoles.