Category Archives: Dam Building

Leaks in Dams: How to Save Water, Time and Effort

From large hydroelectric sites to private decorative reservoirs, dams are invaluable geographical areas. Given their various applications across industrial and agricultural settings, there’s no doubt that dam structures should be assessed and monitored on a regular basis.

Interestingly, one of the main problems that hydro engineers, contractors, and dam owners face is leaking. Even though dams are normally expected to lose water – often due to sedimentation, seepage, and evaporation – leaks in dams can be unpredictable. We should note that reservoir sedimentation is defined as the process of accumulating sediments or solid materials, which can lead to decreased storage rates and eventual abrasion of dam components. Seepage, on the other hand, is defined as the water movement from the upstream face of the reservoir to its downstream surface.

In contrast, leakages occur when water escapes through an opening, such as a hole or a crack. Leaks in dams can be caused by various issues, such as erroneous design principles, inappropriate cut-off trench under the embankment, use of unsuitable soils, failure to remove vegetation, aging, and poor maintenance. Leaking dams are detrimental not only to farm life and economies but people’s health. The collapse of the Whaley Bridge reservoir in the UK proves that dam leaks pose a threat to life.

Due to the uncertainties around dam leaks, professional help and on-site inspection are crucial. Because if one is unable to identify the cause of the problem, any experimental solution will be unsafe and wasteful!

Risk Assessment, Client Communication, and Investigation – Essential Steps to Fixing Leaky Reservoirs

Risk assessment and investigation are the first steps to treating leaks in dams. Sometimes the problem is obvious; the dam doesn’t fill in adequately, water is escaping through the walls, recent storm damage, and so on and on. In some cases, subtle markers, such as unusually healthy crops below the reservoir, might indicate leaks. Daily measures can also help owners calculate how much water is being lost, and how much of the daily losses are due to leaking.

Nevertheless, if leaks in dams cannot be identified easily, professional help and on-site investigation are mandatory to help earth dam owners to solve the right problem and find a balance between costs and effectiveness.

Thus, client-contractor partnerships should be based on trust. While contractors should always propose strategies that are economically sound and effective in the long-term, clients should be willing to provide transparent information and embrace new strategies.

Muchalinda Dam: Changing Direction and Strategy | A Case Study

The beautiful Muchalinda Dam is a powerful example of changing direction and strategy, a process in which dam owners and experts should build a relationship based on trust and transparency. Here we should mention that Muchalinda Dam, located near the Buddhist Monastery in Wilton, New South Wales, has a total area of 2404 square meters.

An initial assessment proved that the dam was leaking significantly. During a two-week inspection, experts noticed a loss of 800 mm or 1% of its total volume, as well as an increase in the sitting groundwater levels. Interestingly, the presence of such alarming markers often indicates that internal holes, such as pipes and tunnels, are increasing in size. Note that piping or tunneling occurs when seepage causes a line of weakness, which might create an opening.

Yet, the experts involved in the initial assessment of the Muchalinda Dam were not given comprehensive pieces of information. It became clear that the information regarding the clay content in the dam and its low-level mark were inaccurate, and the leak wasn’t caused by problems in the upper band. Further evidence showed that the Muchalinda Dam was originally designed to provide a road base, not to contain water. Not only the initial structure had a different use, but after a solid rock shelf had been hit, further activity was stopped and the rubble was pushed into what is now the leaking dam wall.

Additionally, experts detected the following errors:

• Use of heavy machinery on sandstone, which can cause cracks
• Rock spoil rolled into a dam wall
• Lack of soil compaction
• Use of porous non-clay materials

Furthermore, as the dam hadn’t been keyed into the rock, seepage-induced piping and saturation undercut were detected.

Based on the collected data and the Mohr-Coulomb Failure Theory used to analyze rock mechanics and failures, experts proposed three strategies to help to fix the leaks in dams:

• Demolish the dam
• Fix the leakage
• Leave it as it is and report the dam as a dangerous facility with structural flaws

In order to fix the Muchalinda Dam, though, experts insisted on changing direction. They suggested the following steps (as opposed to using a wet blanket):

1. Drain the dam (24 hours)
2. Spread bentonite and clay (7 days) to cut water supply to sub-surface pipes
3. Roll-in bentonite (5 days)
4. Refill the dam (24 hours)

Here we should note that, if left untreated, it’s expected that the wall of the Muchalinda Dam will collapse within 12 months.

Leaking Dams: Long-term Solutions and Safety

When it comes to leaks in dams, dam owners can decide to demolish their dam or tackle the problem. Neglecting a leak, though, can only endanger public and environmental safety.

As mentioned above, various causes and solutions to a leaking dam exist. Some of the common strategies to repair a leak in dams include the use of:

• A plastic membrane liner
• Concrete linings
• A local clay liner
• A bentonite clay liner
• Compacted earth clay linings
• Sealants, such as gypsum or sodium tripolyphosphate
• Bituminous sprays or coatings
• Polymer plugs

That said, building a new dam in a place with suitable soils can sometimes be cheaper and allow changed land use. 

Interestingly, bentonite, the material proposed for the repair of the Muchalinda Dam, is defined as an active liner, a type of flocculate clay. This type of white clay expands 400 times its weight by absorbing water and can be used to fill a void as a comprehensive seal. Moreover, the bentonite clay is eco-friendly and cost-effective; it absorbs different chemicals and can stop toxic materials from reaching crops and plants.

If dam owners decide to use bentonite clay as advised by experts, they can choose between two methods: wet blanket and dry blanket strategies. When employing the bentonite dry blanket method, the bentonite is spread over the dam area at a rate of approximately 15 kg/m2. If the dam contains rock, though, the rock should be covered with at least 300 mm of compacted clay mixed with bentonite.

The bentonite wet blanket method, on the other hand, does not require dams to be emptied. The bentonite is spread over the water surface at a rate of 30 kg/m2. Yet, this method can be unpredictable, with a success rate of 70%; and when it comes to water management, dam owners should aim for 100% effectiveness, especially in arid areas.

Risk Assessment, Client Communication, and Repair of Leaks in Dams: Conclusion

Water losses can have numerous negative effects on both local and global levels. Though many new dams are expected to lose water through evaporation, sedimentation, and seepage, leaks can be unpredictable and dangerous. While some leaks are obvious, some problems are difficult to detect. Thus, professional help and risk assessment are crucial to help dam owners to choose the right solution to their problem.

To repair leaks in dams, experts can employ various strategies, such as building a new dam, using polymer plugs, or applying bentonite clay. In fact, bentonite is considered one of the most effective and active materials to improve dam design, water management, and safety.

Many times problems are caused by erroneous design principles and poor maintenance, which can be embarrassing to workers, contractors, owners, and users at the same time. Thus, transparent communication becomes essential to help all the parties involved build a relationship based on trust. In the end, expertise and trust go hand in hand, so dam owners won’t spend their resources like water.

Have you heard about safe water-covers also known as dam covers? They are used in areas where dams and other large storages of water are the main sources of clean drinking water. In South East Queensland, they are used to reduce the loss of water into the atmosphere (evaporation).

The amount lost in a single year is equal to a day’s consumption. Besides, the growing population of those living in Australia shows that there’s a need to find new ways of preventing such huge losses of water. Take a look!

Methods of Reducing Loss of Water into the Atmosphere

Here, we will talk about two ways of reducing the loss of water into the atmosphere. Their use has been tested and reviewed by different scholars. They are:

1.    Using Suspended Dam Covers

It’s easy to identify these sheets because of their weight and long-lasting nature. They are also made from either a shaded screen full of little holes or a thick plastic. When installing, place them from left to right on the water surface using steel wires or poles for support.

They are known for preventing sun rays from hitting the water surface. This causes a decrease in the thermal energy getting into the dam or pond. The end result is a reduction in water temperature and any chance of it changing to gas. They can even reduce water vapor pressure by controlling wind force.

2.    Use of Floating or Modular Dam Covers

To stop the changing of water from liquid to gas, the use of flat sheets or modular dam covers is another good method. They block sun rays and prevent the entry of vapor from all directions. Now, the difference between them and suspended sheets is that they are just supported by the water. However, for larger dams, you’ll need to use stronger supportive systems.

Another difference between the two is that floating dam covers cannot survive the effects of strong winds. That’s why they are used in small water storage systems. Tests on larger sources are still being carried out.

Are these dam covers good enough? We need to point out that floating covers don’t fully cover the surface of water. This allows vapor to escape through the few available spaces. It also means that there’s lesser use of energy, and winds can still blow away the moist air.

We’sve also discovered that these covers will only allow small amounts of oxygen to get into the water compared to suspended sheets. This is because of the open spaces in the floating structures. Other factors that affect their use include their design, construction materials, and shape.

Types of Dam Covers You Can Get in Today’s Market!

In Australia, there are four key types of floating and suspended covers that are easily available and simple to use. They include:

Brands of floating dam covers available in Australia include ‘E-VapCap’ and ‘AquaCap’. For suspended sheets, these are ‘SuperSpan’ and ‘NetPro’. All of them are dense and don’t allow entry of liquid or solid substances.

How to Reduce Release of Vapor in Dams

There are a lot of studies explaining the different ways of reducing the release of water into the atmosphere. Many of them show that using floating and suspended covers is the best way of preventing the escape of vapor. They explain how they decrease strong winds and reduce the effects of solar radiation.

These studies show that dam covers such as ‘AquaCap’, have a 60% usage rate. They not only reduce water temperature but also do an excellent job of killing different types of seaweeds. Other covers from the ‘E-VapCap’ company reduce the rate of evaporation by 95%.

While all available studies have focused and increased their efforts on the water-conservation efficiency, very few have talked about how they affect the surrounding conditions. Therefore, here, there’s a need for more improved research. This will help in approving their use, especially in large-scale holding tanks and ponds.

What Do Advanced Tests Say?

According to 2007 studies, an increase in surface area will makes it difficult to fix in these dam covers. Using the Wivenhoe Dam scholars also learned that:

With water surfaces above 67m, the dam recorded a 107.514km2 surface area and a water-holding level of 1,165,238ML

The same year, water surface level was between 50 and 53m above sea level

It also showed wind speeds of 10 m above sea level with vapor and air temperatures of 1.2m.

The Measuring Formula

People have used different calculations in measuring the loss of water into the atmosphere. In the above tests, the Penman-Monteith Equation proved to be quite effective. This formula puts into account changes in heat as well as other important things such as: Vapor pressure, Air temperature, and wind force or speed

How Do These Dam Covers Affect The Surrounding Environment?

We need to mention that these covers can cause serious problems to the surroundings. A good example is the Wivenhoe dam which supports a lot of animals and plants. Here, by blocking entry of sun-rays, plants will lack enough sunlight needed in making food. This will also affect the animals which rely on these vegetation for sustenance.

In almost the same way, low oxygen supply lowers water quality and kills other living creatures like the fish living in the pond. Besides, while preventing entry of sunlight has greatly reduced the levels of seaweed, other dangerous effects have been almost impossible to ignore.

For example, contaminating the water in the dam, which is located upstream, can seriously affect the lives of those living downstream. So, there’s a need for more improved studies on the use of these dam covers to make sure that they don’t destroy both plant and animal life.

Are They Affordable?

Did you know that floating and suspended dam covers can last for ten years? They require lower costs of installation and maintenance. Also, since they float freely on large and small-scale water surfaces, you won’t need to pay for more supportive systems

However, for larger areas of water, remember to put in place one or two supportive systems. Fencing is another extremely important step you will need to do. Although it’s something many forget to do, we have found it to be a brilliant way of keeping out humans and wild animals. Besides, it also protects the overall structure of the dam covers which makes them last for a long time.

Installation Problems

It’s important to maintain high levels of safety as you install either floating or suspended sheets as dam covers. Although water bodies will not look the same once you are through, understanding the importance of using them will help you to establish strong safety measures.

Here are other problems that come with the installation of floating and suspended dam covers.

Fear that these covers might detach and damage dam gates

The dam covers might be ineffective when piled up together

Some blocks are hardly operational and only destroy the structure of the covers

Differences in how they respond to changes in weather

Due to few information on the importance water covers, their application on large water surfaces is low

Some are expensive and unavailable

Areas Which Call for More Research

There’s still a lot to do in the study of floating and suspended dam covers. For instance, the physical side of these covers requires a long testing process. Here, some of the areas to keep in mind are:

The ability of gases and liquids to flow through

How much do they damage the quality of water?

Which supportive methods will you need?

Calculating wind reduction and solar radiation levels.

Remember that the installation location of these structures should be carefully studied. This will make sure the water quality and ocean life is not greatly affected. “So, are they easy to install?” This is another issue that continues to trouble many people.

Well, many believe that floating structures are easier to fix unlike the suspended sheets. “Just push them from the shoreline or throw them over the boat,” they say. Unfortunately, we’ve found that this is not always true. Both of them require a well-developed installation process if they are to function properly.

Wrapping Up!

You can now see the importance of using floating and suspended dam covers in reducing the release of water vapor into the atmosphere. Although they are sometimes quite expensive and some have high installation costs, they still have an extremely important role to play in evaporation reduction.

So, maintaining safe operation and the use of these covers should be looked at carefully before anything else. This will secure aquatic life and prevent unexpected damages in the dams or ponds.

Lastly, you can see that these are reliable and effective ways of conserving water. Furthermore, their use and availability will help us to avoid misusing this precious commodity not only in the region but in larger Australia. Good luck!