Ponds and retention basins go through a maturing process that often results in less than ideal water conditions due to the accumulation of organic materials, excess nutrients and human impacts. Knowing the four stages of change and what is happening will help you decide which actions to take for improvement.
The aging process of a pond is a cycle of change called eutrophication. Nature eventually wins and water bodies are gradually converted into marshland. The speed of this process is largely impacted by the input of excessive nutrients and the reduction of depth caused by the accumulation of soil. The first phase of a new pond or retention basin is called the oligotrophic stage. Once the pond is filled it might have Caribbean clear water (see right to the bottom) and very little pond life present until it starts to warm up and algae starts to grow. This is not a bad thing, you are witnessing the development of the food chain and because green algae has little competition at this stage for nutrients from other plants, it starts to grow.
Here is a check list for actions to take:
– Please don’t apply chemicals to the water, let the natural process get established.
– Prevent soil erosion, plant ground cover and encourage terrestrial plants to grow at the water’s edge. Put the weed wacker away.
– Avoid the use of lawn fertilizer near the pond, it might grow more algae.
– Introduce forage minnows like fatheads or shiners to feed on insects and to act as an aquatic barometer for water quality. Minnows become food for larger fish.
– Place a couple of chairs by the pond and relax, maybe cook some marshmallows.
The next phase is called the Mesotrophic stage. You may simply call it the enjoyment phase, it’s the reason you wanted a pond in the first place. The water looks like pond water because it has microscopic plants and animals thriving in it and the bottom has a healthy distribution of aquatic weeds that secure the bottom soil and offer aquatic critters an underwater housing development. Weeds are good until someone who owns a swimming pond jumps in and touches them with a bare foot, let the screaming begin. Fish are cool to watch and usually accept a free meal with little complaint. Seldom will you notice dead fish on the surface in the summer or after ice out.
Check list of observations:
– The pond bottom has an active layer of aerobic bacteria and micro- organisms that consume expired plant material and deciduous leaves. Little or no organic sediments are visible
– The soil on the bottom is clay colored and not black. No rotten egg odor is noticed.
– Aquatic weeds are present but not a nuisance.
– Algae occurs at times but goes away.
– No duckweed is present.
– Soil from surface runoff or a creek is not filling in pond.
– No hydrogen sulfide or septic smell from the water.
The third progression of change for a pond is called the eutrophic stage. Based on our field observations this is when several less desirable changes start to become apparent. Eutrophic ponds tend to produce more aquatic plants, aquatic animals and algae due to the availability of excess nutrients like nitrate, phosphate and ammonia. If your pond has reached this stage or you are considering purchasing property with a eutrophic pond you have a few options for improvement.
– First determine the nutrient load by having the water tested for nitrate and phosphate. This may need to be done once a month.
– Measure the depth of organic sediments (black muck) on the bottom at three locations along the edge of the pond. Mark these spots for future reference.
– Hire the right person if you need help. Not all pond people are educated equally.
– Determine how the nutrients are entering the pond and minimize these sources.
– When possible avoid chemical treatments, they can create residual problems.
– Determine if an aeration system is needed to help with restoration.
– Avoid turning your pond into a science experiment. Know what to use and measure the progress. Maintenance is necessary at this stage.
The hypereutrophic stage is when you need to determine if restoring the pond is going to be worth it. You might think of a pond at this stage as a swamp. Swamps are rich in nutrients and very diverse with wildlife but not great to swim in. The process of biological restoration might take years and be costly so it would be wise to consider draining and cleaning out the pond with machinery. If dredging is not an option here is a process to implement.
– Evaluate the water for nutrients and measure the depth of organic sediments at multiple locations around the pond.
– Determine how much of the sediment layer is organic verses soil with a Volatile Suspended Solids test (VSS).
– You may need to use aeration to supplement the organic reduction process. It is possible to push air through poly hose over 2000 feet if the power source is not close the pond. Windmills and solar aeration systems have limited output.
– Educate yourself before selecting biological products to reduce nutrients and organic sediment. Very few work as advertised.
– Obtain a quote to dredge the pond or to make a new one.
We have been involved with many pond restoration and maintenance projects during the last twenty four years. Our advice is non-biased and comes from real field experiences. If you need suggestions or someone to help you restore your pond please contact us.