Dead fish at Ho Guom:

While many people believe that Sword Lake was heavily polluted, Prof. Ha Dinh Duc - who closely associated with this lake explained, dead fish is a natural phenomenon; There should be no conclusions about Ho Guom ecological environment and no intervention.

- As a long-term attachment to Ho Guom, what does GS say about the mass death of fish over the past few days?

I just thought it was natural. Dead fish are most discovered on 24/7. However, two days later, according to our observation, this situation has plummeted. By the 26th day, the amount of dead fish at the lake was almost gone. We are still in the process of researching to find out the cause and overcome this consequence.

- Many people say that dead fish is caused by Ho Guom's water pollution. And that may also be the main reason for the former, the Sword Lake Turtle has emerged a lot .

To confirm whether the lake is polluted, it is necessary to check and verify the concentration of pollutants in the water. At the very least, we have to re-examine 20 of the 31 standard parameters to assess surface water quality. Currently, there is not enough evidence to confirm that the lake water is heavily polluted. As the turtle emerges, it is natural, it cannot be relied upon to protect the lake water. At the bottom of the mud for too long, the turtles must also float up to get food and get oxygen. That is the law of nature. If anyone wants to evaluate science, it is necessary to have specific evidence, it cannot be indiscriminately concluded.

- Was the cause confirmed due to severe hypoxia? And why is lake water lacking oxygen, GS?

Fish carcass on the surface of Sword Lake (Photo taken on July 28, 2008).Photo: Le Cam

Yes, that's a cause. On 24/7, the DO concentration (water dissolved oxygen concentration) in the water in Ho Guom was determined at 4 points ranging from 0.25 to 0.95, ie below 1. Meanwhile, according to Surface water quality standards, allowable DO concentration for non-domestic water is 2 or more. Thus, the DO level at Ho Guom on 24/7 is lower than the dangerous level causing the fish to suffocate and die too much. However, on the 25th and 26th, when measuring again at 7 different points, we found that DO concentration returned to the permitted level, only one DO score below 1.

Initially, we found that the lack of oxygen could be caused by two reasons. First of all, there are residual oxidized organic matter in the previous sunny days. The second reason, the activity of algae on the bottom of the lake is too strong, leading to the algae sucking out oxygen in the water. Currently the water level in the lake is too shallow. According to our latest measurement, the deepest water level in Sword Lake is approximately 1m60. Thus, it is understandable to run out of oxygen in the water. How is it done and what are the reasons for waiting for testing and research to make it clear.

- So how does the lack of oxygen affect the life of Turtle Lake Sword, especially Turtle?

I can affirm that it has no effect at all. Turtle is a species with high tolerance. According to a study by Cambodian scientists about a species of turtles that have them close to Ho Guom turtle, 95% of the turtle's life time lies under the sand. Therefore, the water environment has little impact on the life and activities of turtles.

- Heard, GS and his colleagues are implementing the project "Research and application of mud pumping technology in Germany to stabilize and restore the environment of some lakes in Hanoi". Why don't we filter and filter the mud for Ho Guom?

How do people try to filter mud? How to change water? It is true that we are studying this project. The partners from Thailand and Japan also jumped in and studied this project with us. However, it has not been included in the application. It is expected that in November 2009, Germany will bring equipment to help us smoke the mud test in Ho Guom. We will try each cell one by one, if we see a positive movement, continue to try another box; but if the situation is too bad, the plan must be canceled.

Moreover, to suck and filter mud, it will cost a lot of money. We don't have enough money to do this now, so we don't dare to recommend it yet. The change of Ho Guom water is almost impossible. Where will water flow? Where can a few thousand blocks of lake water be stored? The destruction of algae under the lake will certainly not guarantee and keep the lake's ecosystem intact.

- So, there is no feasible method to help Ho Guom overcome this situation?

Not sure. We know that the Sword Lake has two main entry gates. A tribute to the Water Puppet Theater. This door has been sealed for a long time. There is a drain on Hang Khay, the water level is always higher than the drain level. I have come up with a plan to build this gate with a door like an irrigation door, which can be lifted off. In the rainy season, the door will be lifted, the lake water escapes in part, the rest is mixed with rain water, oxygen will be conditioned in this way. Every year we do this once, I guarantee that the amount of oxygen in the pool water is always regulated. I can confirm that up to now, this is the most effective, most feasible and inexpensive way. But somehow, I have proposed this plan for many years but have not seen any static construction.

But in my opinion, this is only a natural phenomenon, human intervention is not necessary. So far, we do not have any feasible solution for this. On the 24th, dead fish emerged quite a lot. DO levels in the water that day fell to the lowest level. However, through the rain the next day, the amount of DO we measured returned to the allowable level. And these days, through measurements, we have not seen any phenomenon of low DO concentration. Thus, this is an activity according to the law of nature. In my opinion, it is best to naturally adjust yourself. People sometimes shouldn't interfere too much with nature.

- Thank you, GS!