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Man-made Reservoirs

Man-made reservoirs, sometimes called artificial lakes, are important water sources in many countries around the world. In contrast to natural processes of lake formation, reservoirs are artificial, usually formed by constructing a dam across a river or by diverting a part of the river flow and storing the water in a reservoir. Upon completion of the dam, the river pools behind the dam and fills the artificially created basin (UNEP 2000). Seasonal changes of runoff and precipitation feed the reservoir. There are big differences in the size of man-made reservoirs such as big artificial lakes or small pond-like waterbodies. The stored water can be used for irrigation, drinking water after purification, or to produce energy.

Introduction

On-stream storage reservoir formed by a dam across a valley and its water cycle

A reservoir is an artificial lake called a man-made reservoir. It can be formed by building a dam across a valley, by excavating the land, or by surrounding a piece of land with dykes and diverting a part of the river flow into the reservoir. The water is stored in the reservoir and can be used for irrigationhydro-power, or as a water source for domestic or industrial use. Man-made reservoirs are also very effective constructions to control unexpected floods (see also stormwater management). A reservoir is fed by precipitation, rainwater runoff, or a constant flow of a river. Water loss can occur due to evaporation (especially in arid regions) and depending on the reservoir bottom due to percolation (small reservoirs are often linked). Sediments from rivers or surface runoff can reduce the storage volume of a man-made reservoir significantly (FAO 1992).

Water stored in a valley usually has a higher level than the valley bottom downstream of the dam. Because of this difference in level, the valley can be irrigated by a gravity system or other distribution systems. Water can be taken from the reservoir via a concrete or steel pipe. This pipe connects the reservoir to an irrigation canal downstream. A valve is usually located on the upstream end of the pipe to control the discharge of water into the canal (FAO 1992). The kinetic energy of reservoirs is often used to produce electricity (see also hydropower small-scale and hydropower large-scale).

Ecological Impacts

Where no such water body previously existed the presence of a reservoir in a drainage basin and the abstraction of significant water amounts for storage upstream significantly impacts the watercourse, the flora and fauna, and the human inhabitants in the drainage basin. These potential impacts should be identified and thoroughly examined prior to reservoir construction, in order to comprehensively assess the total value of the reservoir project. Procedures to identify and properly evaluate potential environmental, social, and economic consequences of reservoir construction involve the so-called ‘Environmental Impact Assessment’ (EIA). Such an assessment is now obligatory by law in many countries for all new dam constructions (UNEP 2000).

Ecological impacts of reservoir dams have been reported from various aspects such as barrier for migratory animals like anadromous fish, eutrophication of reservoirs by plankton blooming, decreasing flow volumes in tailwaters, stabilization of flow regimes by flood peak cut, changes in thermal regimes of river water, river bed degradation and increase in substrate grain size by sediment trapping, etc. (TAKEMON 2006). Furthermore, big dams and the extraction of water (e.g. for spate irrigation) can create riparian conflicts (see water conflicts). Also, read the paragraph “Impact on Environment” in the rivers factsheet.

Comparison of the riverbed landscape between upstream and downstream reaches of the Yasugawa Dam in the Yasu River in central Japan. The dam is as old as 53 years and the distinctive riverbed armouring can be observed. White part of rocks indicates thick accumulation of organic matter originated from the reservoir
Comparison of the riverbed landscape between upstream and downstream reaches of the Yasugawa Dam in the Yasu River in central Japan. The dam is as old as 53 years and the distinctive riverbed armoring can be observed. The white part of rocks indicates a thick accumulation of organic matter originated from the reservoir. Source: TAKEMON (2006) 

Basic Design Principles

Factsheet Block Body

Adapted from UNEP (2000)

Different types of reservoir systems.
Different types of reservoir systems. Source: UNEP (2000) 

Like lakes, reservoirs range in size from pond-like to very large water bodies (e.g. Lake Powell, U.S.A.). The variations in type and shape, however, are much greater than for lakes. The term ‘reservoir’ includes several types of constructed water bodies and/or water storage facilities:

  • Valley reservoirs – created by constructing a barrier (dam) perpendicular to a flowing river.
  • Off-river storage reservoirs – created by constructing an enclosure parallel to a river, and subsequently supplying it with water either by gravity or by pumping from the river.

The latter reservoirs are sometimes called embankment or bounded reservoirs and have controlled inflows and outflows to and from one or more rivers. In addition to single reservoirs, reservoir systems also exist and include cascade reservoirs – consisting of a series of reservoirs constructed along a single river, and inter-basin transfer schemes – designed to move water through a series of reservoirs, tunnels, and/or canals from one drainage basin to another.

Pumping from a Reservoir for Irrigation

Adapted from FAO (1992)

A small reservoir in the hills of Tepoztlán (Morelos, Mexico), which is mainly filled by precipitation catchment. The water is extracted by gravity and is protected by a fence to avoid contamination from animals or unauthorised use. The reservoir is sealed with an impermeable liner
A small reservoir in the hills of Tepoztlán (Morelos, Mexico), which is mainly filled by precipitation catchment. The water is extracted by gravity and is protected by a fence to avoid contamination from animals or unauthorized use. The reservoir is sealed with an impermeable liner. Source: STAUFFER (2009) 

The fields located around the reservoir upstream of a dam or surrounding a natural lake are higher than the reservoir or lake’s water table. Here irrigation is only possible with the help of pumping stationsmanual or motorized pumping.

The water level in the reservoir is usually highest at the end of the rainy season, and lowest at the end of the dry season or the irrigation season. Pumps installed at reservoirs and lakes must be able to handle these fluctuations, which are not only vertical but even more pronounced horizontally because the water recedes back to the lowest parts of the reservoir. A dead branch of a river can also be made to function as a reservoir. The branch is filled with water during the wet season and closed off during the dry season so that …

10 Tips for Buying a Tank

This section is designed to help you make an informed decision and choose the best tank for your needs, ensuring that it continues to do an effective job for many years to come.  It’s also vital to know that a water tank is made of the right material for your family’s health and local conditions.  Ask your agent or manufacturer if your poly tank meets and contact us for more information.

Enduraplas Blogs | Water Storage & Rain Harvesting | Buying a Water Tank

Polyethylene Storage Tanks for Water & Chemicals? They will be able to show you a copy of their certification or the tank will be clearly marked as being licensed to the standard.  

The standard isn’t mandatory, or necessarily applicable depending on your tank material, here are some great questions to ask when buying a tank to ensure you’re getting a quality product:

Where was the tank made?

Some imported tanks are made from material that isn’t suitable, might not have a warranty, or include fittings that are difficult and expensive to replace.

Is the plastic used in the tank certified as safe for drinking (potable) water?

Whether it’s just the lining or the entire tank, properly certified polyethylene is safe for drinking water. Unfortunately, some imported tanks may not be made from a material that has been properly tested.  It is important to note that some councils do not allow tank water to be used for drinking.

Does the manufacturer maintain a product trace system?

Good manufacturers will be able to trace your product to its source materials and will hold records of when and where it was made.  They will also be able to provide details of the tests it underwent before leaving the factory.

Does the tank have a warranty?

Don’t be seduced by lengthy extended warranties. Ten years is a very reasonable warranty period for plastic tanks.  Steel and concrete tanks typically have longer warranty periods, 10-20 for steel and 20-30 for concrete. Carefully read the conditions and installation instructions before you buy so that you know your rights and obligations should you ever need to make a claim.

Has the tank design been tested?

Like any material, plastic has some limitations when it is placed under stress (by filling). It’s important that your tank has been well designed and properly tested to ensure it’s suitability for purpose.  Although steel and concrete are stronger materials, it is still important to make sure the design is suitable.

Is the stated capacity of the tank calculated according to the Standard?

The calculation in the standards ensures that manufacturers can only state the actual amount of water that can be stored in the tank once fittings have been installed.

How should I maintain my tank and installation to ensure my warranty remains valid?

Your manufacturer should provide you with written guidelines to help you maintain the base fittings and installation of your tank so it will last and continue to provide excellent quality water storage.

Has the thickness and colour of the plastic been calculated according to the Standard?

The Standard sets strict guidelines concerning the thickness and colour of the material to prevent light entering the tank as this can lead to algae growth.

Does the plastic contain UV protection specifically for our Australian climate?

Our local climate can be incredibly harsh.  Polyethylene is ideal because it contains UV-stabilizing ingredients.  It’s important to check whether the polyethylene used in the manufacture of your tank has been made in Australia. Polyethylene made in Australia has more than twice the UV protection called for in the Australian Standard so you can be sure it is suitable for the tough Australian conditions.

Is the tank made by a member of the Association of Rotational Moulders?

The Association of Rotational Moulders (ARMA) is a representative body of the majority of leading poly tank manufacturers in Australia and New Zealand. We help our members to maintain their status at the forefront of the industry and to set the leading standards in the water tank marketplace.…

How to Select the Best Fluid Reservoir for your Dispensing Application

Often the fluid reservoir for assembly fluids such as glue, oil, grease, and epoxy is decided by the fluid manufacturer. Many industrial fluids are pre-packaged in syringes, cartridges, bottles, or pails before reaching the factory floor. There are, however, a few recommendations manufacturers can consider when selecting the best possible fluid reservoir for an efficient, productive dispensing process.

Looking at the volume of products you’re manufacturing, the type of fluid you’re using, and types of fluid reservoirs available can help you choose the optimal solution and improve the quality of your dispensing results. Although it’s always best to first talk to an expert fluid application specialist, here are a few recommendations to help along your journey.

Let Your Production Volume Be Your Guide

Production capacity should be a key consideration when deciding what type of fluid reservoir you need. If your manufacturing process requires just one 10cc syringe barrel per station per shift with no issues, there’s no need to look at other solutions. If you find your process requires multiple 10cc syringe barrels per station per shift, it may be time to opt for a larger syringe, cartridge, or even a tank to reduce the downtime it takes to swap out smaller syringe barrels frequently throughout the day.

Keep in mind that dispensing syringes and cartridges may still be the best option regardless of production capacity. It depends on the material being dispensed. Because syringe barrels and cartridges are disposable, they’re easier to handle with minimal clean up or maintenance.

  • Recommendations for Low-Volume ProductionFor low-volume production or very small, precise deposits, you’ll likely need a 3cc to 55cc syringe barrel. For low- to medium-volume production with high-viscosity materials, you’ll more often use a 2.5 oz to 32 oz (75 ml to 960 ml) cartridge. For lower viscosity/self-leveling materials, a tank may be considered.
  • Recommendations for Medium-Volume ProductionFor medium-volume production with lower viscosity/self-leveling materials, a 1-liter (0.26 gal) or 5-liter (1.32 gal) tank would be optimal. For high-viscosity materials, a cartridge may still be the best option.
  • Recommendations for High-Volume ProductionFor high-volume production and/or larger deposit sizes of lower viscosity/self-leveling materials, a tank is the best option. For high-volume production with high-viscosity materials, a ratio pump should be considered.
Cartridges Filled

Bigger Fluid Reservoirs Aren’t Always Better

It may seem like choosing a bottle or pail instead of a dispensing syringe or cartridge would increase production since it may not require replacing as often. However, certain considerations such as cleaning and wasted material should not be overlooked.

If the fluid tank you select doesn’t have a replaceable liner or accept pre-filled bottles or pails, cleaning becomes a problem, especially if the fluid is an adhesive or reactive fluid. The time it takes to clean the tank to prevent material from hardening or contaminating new material could surpass the time it takes to switch out a pre-packaged syringe or cartridge.

Fluid waste is another consideration. Industrial syringe barrels and cartridges are designed to minimize fluid waste. When fitted with perfectly matched pistons, fluid can be dispensed completely with hardly a trace residue left in the reservoir. This is important when your process requires an expensive, specialized assembly fluid.

Useful Tip: When selecting a fluid tank, always opt for a tank with a liner and a large opening that makes it easy to clean. Or opt for a tank that accepts pre-filled bottles or pails to make replacing the fluid fast and easy with no cleaning required.

Tanks are Great, but Only with Pourable Fluids

Fluid viscosity is another key consideration when selecting the optimal fluid reservoir for your dispensing application. Whereas fluid cartridges and syringe barrels can handle any fluid viscosity, fluid tanks only accept pourable or self-leveling fluids, otherwise known as low- to medium-viscosity fluids. This can impact your process when, for example, you have a high-volume production capacity and a high-viscosity fluid.

When this is the case, a ratio pump is often the best solution since it accepts pre-filled 5- and 55-gallon drums and provides up to 2500 psi (172 bar) of pressure to promote superior flow of thick fluids to the dispensing equipment.

If you have a low- to medium-volume production capacity and a high-viscosity fluid, a dispensing syringe or cartridge is best because the piston helps dispense the material evenly for accurate, repeatable results.

If you put a thick material such as petroleum jelly into a fluid tank, the tank’s pressure may introduce air tunneling into the material since the air cannot be applied evenly onto an uneven surface. This would result in inconsistent material deposits, which could create unnecessary rework and rejects.

Dispensing Method and Fluid Type Also Matter

Sometimes the method of application influences the type of reservoir you should use. For example, if the application requires a manual dispensing method, it’s often easier and more ergonomic for the operator to hold a syringe barrel as opposed to a dispense valve with air and fluid tubing connected.

On the other hand, if you have an automated cyanoacrylate or fast-curing glue application, you would likely opt for a tank as opposed to switching out multiple syringe barrels per shift. But if you had an automated silver-filled epoxy application, you may not have a choice. You may have to switch out multiple syringes barrels because of the nature of the fluid itself. Fluid reservoir selection often depends on a combination of factors, including the dispensing method, the type of fluid, and requirements of the application.

Fluid Reservoir Troubleshooting

One common pitfall when selecting a fluid reservoir is choosing a fluid reservoir without a precision pressure regulator. This often leads to inconsistent dispensing results because when you set a non-precision pressure regulator at 40 psi, it will fluctuate from 35 psi to 45 psi throughout the course of a day.

Nordson EFD fluid tanks feature precision fluid pressure regulators, which essentially means if you set one at 40 psi, it will maintain constant pressure for a much more precise, repeatable dispensing result. This creates the …