In summer, the warm surface waters and the cold, dense bottom waters remain completely separated from each other, forming a barrier known as the thermocline. The bottom waters are isolated from the atmosphere, and as sediments and organic matter decompose, they continuously deplete dissolved oxygen, plunging these waters into a state of severe hypoxia.

What are the consequences of this oxygen-depleted condition? As a typical seasonally stratified reservoir, the Kamancheh Reservoir experienced the release of oxygen-depleted water between 1986 and 1990, resulting in the death of over 300,000 salmon fry at downstream fish hatcheries. This ecological disaster became a key driving force behind the investigation and application of ultra-nano-aerosol reoxygenation technology in this reservoir.

 

So, how do hypoxic water bodies form, and what are their hazards? And what role can the ultra-nano-aerosol re-oxygenation system play? This article will provide you with a detailed explanation.

Toxic substances are released from sediments.

Hydrogen sulfide: Under hypoxic conditions, anaerobic bacteria decompose organic matter, producing highly toxic hydrogen sulfide. This gas is extremely poisonous to fish, damaging their gill tissues and nervous systems—even at low concentrations, it can be fatal.

Methylmercury: In the same anaerobic environment, conditions are ripe for certain bacteria to convert inorganic mercury into methylmercury—a form that is far more toxic. Methylmercury tends to accumulate along the food chain, posing a long-term threat to fish and organisms that feed on fish, including humans.

Iron and Manganese: Subsequently, metals such as iron and manganese will leach from sediments under anaerobic conditions. Although these metals are relatively low in toxicity, they can cause discoloration of the water, produce unpleasant odors, and form a deposit film on the surface of fish eggs.

The Kamanche Reservoir does not have a multi-level intake tower; its sole deep-water outlet happens to be located precisely within this oxygen-depleted, uniformly warm layer. This means that all the water released downstream into the Mokelumne River and the fish hatchery is precisely this “poisonous water”—water rich in hydrogen sulfide, methylmercury, and excessive metals.

What will the downstream fish hatchery face at this time?

Fish egg asphyxiation and poisoning

The development of fish eggs requires a continuous supply of clean, oxygen-rich water. Toxic substances such as hydrogen sulfide can directly poison fish eggs and newly hatched larvae. Meanwhile, the already low dissolved oxygen levels in the water body cannot meet the respiratory needs of the fish eggs, leading to suffocation.

Sediment cover

The bottom water released from the reservoir contains a large amount of suspended particulate matter (high turbidity). These particles settle down and cover the fish eggs, obstructing their breathing and waste removal, ultimately “suffocating” the eggs to death.

 

In summary, the hypoxic conditions at the bottom of the reservoir have created an “internal pollution source” that is directly discharged through the outlet into the downstream fish hatchery, thus forming a typical and deadly ecological disaster chain.

How the Ultra-Nano Aerosol Re-Oxygenation System Can Resolve the Crisis

The application of the ultra-nano-aerosol reoxygenation system in the Kamanchi Reservoir is not merely a matter of increasing oxygen levels—it is an ecological engineering technology that precisely targets the root causes of the aforementioned disaster chain. So, how does it work?

Direct action: Injecting oxygen directly into the “source of toxicity.”

The ultra-nano-aerobic system dissolves pure oxygen into water drawn from the bottom layer, then re-injects this oxygen-rich water flow into the homothermal layer in the form of a horizontal jet through a diffusion pipe positioned above the sediment.

 

When oxygen is delivered to the lower layers, it immediately reacts chemically with hydrogen sulfide, oxidizing it into non-toxic sulfate. This effectively cuts off the supply of hydrogen sulfide at its source. Meanwhile, the presence of oxygen inhibits the activity of anaerobic bacteria that produce methylmercury, thereby significantly reducing its formation.

Dissolved iron and manganese, upon encountering oxygen, are oxidized to form insoluble solid particles that precipitate back into the sediment, thereby being removed from the water body.

Indirect effects: Improving the overall aquatic ecosystem

Bottom-layer reoxygenation reduces the release of nutrients such as phosphorus and ammoniacal nitrogen from sediments. If these nutrients are brought to the surface layer during autumn water mixing, they can serve as "fuel" for next year's algal blooms. Therefore, the ultra-nano-aerosol reoxygenation system fundamentally reduces algal biomass by controlling internal pollution sources.

 

The ultimate benefits of the hatchery

The ultra-nano aerosol reoxygenation system significantly increased the salmon population during autumn floods, playing a particularly important role in dam migration and artificial breeding processes.

Fish eggs require an ample supply of oxygen for hatching, and the bottom-layer aeration provided by the ultra-nano aerosol re-oxygenation system offers crucial support, thereby promoting the survival and reproduction of salmon.

Between 1996 and 1997, the number of salmon returning each year was approximately 9,100, an increase of 5,550 compared to the long-term baseline of 3,550, demonstrating the system's significant effectiveness.

The number of migratory movements remained steadily increasing from 1996 to 2005 and in 2014, indicating that this growth is unlikely to be the result of natural fluctuations.

Of the 7,000 fish used for spawning each year, 4,231 can be attributed to the ultra-nano-aerobic reoxygenation system, further demonstrating its importance in the recovery of salmon populations.

 

The ultra-nano-aerosol reoxygenation system, when applied to the Kamanchi Reservoir, functions like a precision ecological scalpel. It does not disrupt the reservoir’s stratification; instead, it directly targets and treats hypoxic lesions, oxidizes toxic substances, suppresses endogenous pollution, and improves the overall ecological condition. By addressing the root causes, it breaks the chain of ecological disasters, transforming ecological crises into a model for restoring river ecosystems and promoting river conservation.

Reference materials:

Hypolimnetic Oxygenation 4: Effects on Turbidity in Camanche Reservoir and Its Downstream Fish Hatchery

Hypolimnetic Oxygenation 6: Improvement in Fisheries, Hydropower, and Drought Management with Installation and Operation Costs at Camanche Reservoir, California, United States

Hypolimnetic Oxygenation 3: An Engineered Switch from Eutrophic to a Meso-/Oligotrophic State in a California Reservoir