Down to Earth

Pond Inspections

By Mike Otto

Here in my part of the planet, along the Red River in north Texas, it rained much of May and a lot of June, with totals topping our yearly average.

This is spring time in Texas and big rains are not unusual. The only difference this time is the amount—ponds are full, creeks are constantly running with lots of water and the big rivers were out of their banks.

Our main North South Interstate running from South Texas to the border of Canada, Interstate 35, lapped at the bottom of bridge at the border of Texas and Oklahoma. Experts told us more than 190,000 cubic feet per second was flowing into Lake Texoma at the height of these events.

For perspective, the minimum water bill for most families is about 3,000 gallons per month. There was enough water flowing each day under that I-35 bridge in May to supply one month’s water for almost 700,000 families.

The excessive high water will ultimately be gone into the Gulf of America in a few days, leaving us with a good, full start to the summer.

July and August is a good time to do an inspection of our ponds and lakes, the shore lines, primary spillways, and emergency spillways.

This is what we want:

·       Rain water to hit the ground,

·       Flow into low places to run into our ponds,

·       Fill the pond up to the top, go over the spillway, back into the creek and continue its journey.

What we DO NOT WANT is rain water hitting the ground, rolling fast and eroding dirt. When water moves outside its intended path, or flows over the dam, it will cause erosion problems.

No one wants their dam to burst and wash out the county road downstream, or chew up the backside slope, or the emergency spillway.

This summer, let’s gets our shovel, a pair of rubber boots and head out. It is easy when the water is running in to see what is going on, where it all comes from, and if it all goes where we want it to go. 

Start at the start; where is the water flowing into the pond? Does the drainage area originate on your property or does it come from the neighbor’s land? Along the path where the water is flowing, is there a sufficient vegetation to hold soil? Is the current flow causing any erosion, washing away dirt and creating any holes? If the water continues to flow after the main rainfall, it is advisable to inspect the area again once the water settles into the pond to get a clearer picture what the water is doing.

Keep in mind everything, loose soil, twigs, leaves, and other organic debris above the pond will eventually work its way downstream and fill the pond in. That is the way Mother Nature, with an assist from gravity, works.

We can slow that process down a lot with due diligence, good vegetation and proper care, and that is why we are having this inspection.

Once the water settles into a pond, it acts a little differently. It does not matter if the pond is a quarter acre or one hundred acres. When moving water slows, dirt it picked up will start of drop out. Sometimes it will settle quickly, sometimes slowly, but that is also part of Mother Nature’s job. It happens every time.

This brings us back to our initial point: the healthier the vegetation along the waterways, the less dirt and silt will be carried into the pond, thus prolonging your lake or pond’s lifespan.

While natural processes ultimately prevail, establishing good vegetation and implementing erosion control practices can significantly extend the time before the pond fills with sediment.

Next, you want to look at the water level when it is full. Is it close to the top of the dam, are there trees with water up on the trunk? Look at the dock, walking path, the property line. Does water back up into a field that it is not supposed to be?

If water is still draining over the spillway, re-check the permanent high-water level when it finishes flowing.

A new pond that is filling up for the first time may need some adjustments. The level of the water will be equal on all sides, sometimes it may not look like it, but your pond surface is flat.

The same is true when you buy a new property and see the water level at full pool for the first time.  Look it over carefully and it will be easy to see what needs to be done, if anything.

You are looking for bare soils, eroded areas, places where vegetation or some other erosion prevention needs to be.

Water can NEVER go over the top of a dam. If it does, fast-flowing water will wash the dam out. This is easily adjusted but the first thing we need to know is if any adjustments are needed. 

The top of the dam may have been worn down from years of cattle tromping, wind erosion with no vegetation—even beavers can build a path and cause a weak spot only noticeable when the pond is full.

Although some trees can handle wet conditions, most will die if water remains too high around their base. This makes the present high-water level a good time to identify and mark trees that are too close to the pond. Often, in new construction, the potential impact of the pond’s water level on nearby trees is overlooked, resulting in a delay approach.

Water that is only a few inches or a foot deep around the edge is not a big problem but if you have a foot of water fifty feet from the main body of the pond needs to be fixed.

Managing shallow water is a headache. It will fill with aquatic plants.

A pipe is the most common first line of defense to release excess water from a pond. Most of the time, this primary spillway pipe is set a minimum of two vertical feet below the emergency spillway.  Note: The emergency spillway has its name because it is considered an emergency if water goes over it. Most of these are located at the end of a dam.  

The size of the primary spillway pipe is designed to release the same amount of water that is coming in, and avoid using the emergency spillway…also referred to as the secondary spillway.

When water is getting too high onto the dam, it needs an inspection. The pipe could be too small, or maybe it has some restriction.  The vertical distance from the pipe to the next spillway may not be adequate, or the dam is just too low.

With water running through the pipe does it look to be restricted with brush or tree limbs?  I have seen pipes completely filled by beavers. Pipes can be unplugged and that is a must…but know those industrious mammals will come back and plug it again.

You will see beaver sign around the pond, girdled trees, willows cut down, small limbs skinned of all their bark, sawdust next to a gnawed tree, and pointy stobs where small trees once stood.

Walk the backside of the dam, look closely at the pipe to make sure no water is running beside the pipe. That is not uncommon. It means there is water escaping from the front side without going through the pipe. If water is going around the pipe, that won’t heal.

If that is the case it is only a matter of time before there are some big repairs. Only with a great amount of luck will that be repaired without removing the pipe.

Just as important is water coming out of the pipe that is not entering at the inlet. This is also not uncommon but sometimes it can be stopped without draining the lake.

Most of the time the cause is poor pipe material (corrugated metal) that has corroded and rusted through. This will not show up for a number of years and is a good reason regular inspections are important.

Trees on the back slope of the dam need to be removed as soon as they are spotted. Once they start to mature, roots will grow toward the water. It is easy to see why that is no good.

Trees fifty feet from the backside slope need to be removed also.

Give the emergency spillway a good look, too. Is the vegetation healthy? Cattle must be kept off the spillway, just like the rest of the dam.  They not only eat the vegetation, but often start a trail for water to erode the soils.

Take home points:

·       From upper watershed to where water starts to flow downhill toward the lake everything needs to be inspected, at least yearly. Good vegetation extends the life of the lake. 

·       Keeping silt out is a great exercise but requires action.

·       Once the lake is finished, the first rainfall starts to fill it.

·       The dam and spillway will last decades with good grass cover.

·       Trees are great for shade around the water but never on the back slope or close to the backside toe.

·       A pipe may never go bad, but when it does, it can go fast and require a lot of work, and money, to fix.

·       Just like cattle, beavers have no business being near the lake.

Taking a few minutes now to address these potential issues can save a significant number of headaches down the road.