Useful Information

Lawn Irrigation

Lush, green lawns are not just a pretty feature in a perfectly manicured garden. There are several industries that rely on flawless greens as a core part of their functionality – sport and recreation fields, parks and golf courses are just a few.

Maintaining a perfect lawn, however, can be a complex task, and often requires expert knowledge and skills, as well as a range of specialised machinery and tools.

Aqualine is invaluable as a part of one of the most important aspects of lawn maintenance: good irrigation.

(For more information on Aqualine, see the Aqualine Product Page.)

Groundwater Recharge

An ideal way in which to save water that might otherwise have been wasted is to store it in an aquifer underground. In this way it can be withdrawn when needed.

There are many ways in which water can be returned underground. Historically, groundwater recharge has occurred primarily from the percolation of surface water from rivers and their tributaries. As rivers begin to meander over level ground, water is constantly seeping through the riverbed into the ground. Over time, however, the riverbed can become less permeable as silt deposits increase. At this stage it is possible to divert the river to clear the silt allowing for better penetration.

Different land uses also have an impact on the recharge of the aquifer. When a crop such as sugar cane or timber is planted, the runoff to rivers and streams will decrease as will the rate of ground water recharge. The development of an urban area can increase the runoff which results in less groundwater recharge.

Long-term, large-scale pumping without subsequent replacement of groundwater can result in fissures and land subsidence. This results in damage to roads, railroads, pipelines, houses, dams, etc. While these are all noticeable problems that can be dealt with, the most serious and often over-looked problem of subsidence is the permanent loss of an aquifer’s storage capacity.

Artificial recharge describes the method of storing high quality surface water in aquifers or geological formations that can receive additional water. In this way the level of groundwater is augmented and valuable water is not lost to stream flows or evaporation.

With Aquifer Storage Recharge (ASR), water is actually directed into and stored in the ground. This is done by injecting water into the most permeable parts of the aquifer. The result is that the water is fed underground at far greater rates than would occur under natural conditions.

Aquifer Storage Recovery (ASR)

Aquifer Storage Recovery (ASR) involves collecting water (stormwater, snow melt, etc.) at a time when it is abundant and then transferring it into naturally occurring underground spaces (aquifers) that consist of porous or fractured sediments of rock. The water is stored below ground and is recovered as needed.

Most ASR systems provide seasonal water storage, storing water during the wet season and recovering it later during extended droughts. Increasingly many water managers are constructing ASR systems to ensure reliability during emergencies, whether severe floods, earthquakes, contamination incidents (see Groundwater Contamination below), pipeline breaks, or potential damage due to warfare or sabotage.

Issues to consider are that the water resource must be abundant, plus there has to be a system for collecting it. The aquifer must be able to receive and deliver water at rates that are consistent with the projected use.

Natural water quality in the storage zone ranges from fresh, suitable for drinking without treatment, to brackish, including total dissolved solids. Most sites have one or more natural water quality constituents that are unsuitable for direct potable use except following treatment. Such constituents may include elements which are typically displaced by the stored water as the bubble is formed underground.

ASR provides a cost-effective solution to many of the world’s water management needs, storing water during times of floods or when water quality is good, and recovering it later during times of drought or when water quality from the source may be poor. By storing water in underground aquifers, one reduces or eliminates the need to construct large and expensive surface reservoirs. Due to long term over pumping of groundwater, levels can now be restored as water is recharged.

The main driving force behind the current rapid implementation of ASR technology around the world is water supply economics. ASR systems can usually meet water management needs at less than half the capital cost of other water supply alternatives. It is also important to note that by reducing or eliminating the need for construction of dams, and by providing reliable water supplies through diversions of flood flows instead of low flows, ASR systems are usually considered to be environmentally friendly.

Water is stored deep underground in water-bearing geologic formations, or “Aquifers” that may be in sand, clayey sand, sandstone, gravel, limestone, dolomite, glacial drift, basalt and other types of geologic settings.

Most operating ASR sites are storing treated drinking water. When recovered from storage, this water usually requires only disinfection before being sent out to the water distribution system. Treated wastewater is reclaimed and piped to golf courses, parks, gardens and other areas requiring irrigation to reduce the demand for potable water.

When rains begin and irrigation demand ceases, reclaimed water is stored in ASR wells in deep brackish aquifers, from which it is recovered when needed to meet irrigation demand during dry periods.

Several sites are storing untreated groundwater pumped from overlying or underlying aquifers, or from wellfields located at great distances from the ASR site. When needed, this water is recovered from the storage zone and combined with whatever flows are then available from the primary water sources, to help meet peak or emergency water demands.

Groundwater is increasingly viewed as a desirable application of ASR technology. The newest ASR application is for storage of partially treated surface water. Stored water is recovered to help meet peak demands for supplemental untreated water, whether for urban needs, ecosystem protection, low streamflow maintenance, agricultural irrigation, industrial water requirements, power plant cooling make-up water, or other needs.

Groundwater Contamination

Many developing regions suffer from either chronic shortages of freshwater or the readily accessible water resources are heavily polluted. According to the World Health Organisation (WHO), a large portion of the population in developing countries live in rural and suburban areas where conventionally treated drinking water is generally unavailable (WHO, 1993).

Accelerated population growth coupled with impoverished socioeconomic development with limited water resources and poor sanitation, leads to an increase in diseases associated with poor living conditions among which water-related and water-borne diseases play a major role. Many of the rural communities around the world get their drinking water supply from groundwater sources. The water is drawn from the boreholes and distributed to the community without any prior treatment. People from these rural communities often complain that the water tastes brackish which is normally an indication of poor quality, especially of high salinity.

Groundwater supplies have some advantages over surface water. Groundwater is generally of a more uniform character and relatively free from harmful bacteria. Groundwater can be contaminated as a result of poor solid, liquid and sanitary waste practices. Defective well construction and failure to seal abandoned wells as well as poor groundwater production management are also responsible for pollution.

Contaminated groundwater can still appear clean and yet contain pathogenic organisms; visual evaluation should therefore be avoided. Bacteria in the liquid effluents from the septic tanks and cesspools, to name a few, are likely to contaminate shallow groundwater aquifers if poorly constructed or located with respect to the production borehole. Furthermore, the presence of a shallow or perched aquifer increases the risk of contamination.

Salt Water Barriers

Over the past several decades, excessive pumping has triggered saltwater intrusion, which can threaten that region’s water supplies. As groundwater becomes depleted in the coastal regions, the ocean salt water tends to intrude into the freshwater supplies. This threatens the water for drinking or irrigation as the aquifer becomes contaminated.

Freshwater, being less dense than seawater, tends to “float” on the saltwater. The Ghyben-Herzberg relationship states that the freshwater zone should extend to a depth below the sea level equal to 40 times the height of the water table above sea level.

As freshwater heads are lowered through well production, the saltwater migrates towards the point of withdrawal. This movement of water into zones previously containing freshwater is known as saltwater encroachment.

The result is that wells might have to be drilled deeper in the hope that the water available in a lower aquifer has not also been affected. However, where supply wells are drilled too deeply or are pumped at too large a rate, upconing of the salty water may occur.

It is common practice to inject fresh water into the ground to form a “barrier” or “curtain”. This barrier prevents salt water entering the aquifer by providing a hydraulic barrier to sea water intrusion and permitting the groundwater basin to be safely drawn down below sea level. Some of the water that is pumped into this barrier will dissipate into the ocean, while the majority flows back into the groundwater basin thereby augmenting the groundwater supply.

Under these conditions steel pipes are subject to corrosion and can be difficult to manoeuvre. Even stainless steel pipes are subject to corrosion and internal scaling. The result is that the pumps would have to run for longer periods of time to ensure the same quantity of groundwater is being removed from the offending aquifer.

Because of its construction and the sophisticated use of modern materials, Boreline® is not subject to these effects and can be used continually over many years without any form of degradation.

Groundwater Extraction

Clean potable water is essential to life, yet so many of the world’s population do not have access to it. Problems faced by developers are very similar, namely the lack of large sources of unpolluted or salt-free raw water and the lack of funds.

Dams and pipelines are a tangible indication of money spent while there is a false perception that it is difficult to quantify volumes of groundwater available in most aquifers. This creates uncertainty and results in less spending and this potentially large supply remaining un-tapped.

Traditionally, steel pipes have been used with submersible pumps to transfer water from the depths of an aquifer to the surface. The water is then used for domestic, agriculture or other uses. There have been many problems associated with these heavy, bulky rigid pipes, but users such as, Water Utilities, Mines, Farmers and others have had no choice but to remain with these products.

Problems faced would begin with transporting the pipes to site as large trucks would be required. Installing the pump and pipe would be another time consuming exercise as a large crane with lifting gear are needed to lower the pump and pipe into the well or borehole. Pump removal for repair or servicing is just as frustrating.

Boreline®, is a Flexible Rising Main designed to solve many the problems associated with rigid systems. Because of its inherent characteristics, Boreline® rolls up flat thereby making it light and compact and very easy to transport. A small pick-up truck or LDV can be used to transport the Boreline® to site, immediately reducing the extra costs associated with a larger vehicle.

Once on site, the Boreline® is unrolled and attached to the pump using the available Boreline® couplings. These are available in 316 Stainless Steel (SS 316) or Bronze. The power cable is attached to the hose along the entire length using the available cable straps.

The pump is lifted and lowered into the well. The other end of the Boreline® is placed over a simple rolling wheel and attached to the pick-up. The vehicle is then used to lower the Boreline® into the well in minutes, using only a couple of assistants.

Boreline® has been designed with superior strengths in mind. The result is that the hose itself can support the pump, pipe and water up to a depth of 660ft (200m). No support ropes or cables are required.

Using Boreline® results in immediate cost savings in time and money.

Boreline® also does not corrode or scale internally. The figures for water flow and head losses calculated originally during the design phase are the same figures one gets after years of pumping. Because of its flexibility, the internal scaling which plagues the rigid systems, causing costs of pumping to increase, does not affect the Boreline®.

Removing the pumps for servicing is just as simple, resulting in labour cost savings.

Yield Testing

It is essential to have the yield of a borehole tested for numerous reasons:

• To establish the safe yield of the borehole. (This refers to the yield at which the borehole can safely be pumped).
• To determine the safe yield duty period that the borehole can be operated for indefinitely, without endangering the aquifer.
• To determine the quality of the groundwater in relation to its intended use, the performance characteristics of the borehole and the hydraulic parameters of the aquifer.

How long should the test-pumping take?
The length of the pumping test is directly proportioned to the duty period that the borehole is to be pumped at once the permanent pump has been installed.

For instance, a borehole supplying domestic water to a house will have a shorter duty period than an irrigation borehole. As a result, the type and length of the test pumping performed on a domestic borehole will be shorter than the test on an irrigation borehole.

Test Pumping

The test contractor should issue the customer with a certificate upon which the date, depth at which the test pump was installed, static water level, pumping rate at the end of the test and water colour is recorded.

It is normal to undertake a six hour test and then install a pump with a capacity of around 50-60% of the flow at the end of the test. This 40-50% safety margin is sufficient in most cases, but not always. The end user should always consult the pump installer as to exactly what type of test is the best for his needs.

Greater sophistication and longer water yield tests will cost more. In many cases the extra initial cost can save a great deal of money in the long run. Unless absolutely necessary, never pump the borehole at its full capacity.

Farmers, recreational clubs or commercial or industrial concerns will usually require a higher duty period, and as a result, a longer test. Occasionally the test, for example per 100% duty period, should continue for weeks and even months.

Boreholes to be subjected to a duty period of up to 10 hours per day should be tested for at least 24 hours. Water levels should be recorded at specific time intervals in the pumping borehole, together with the pump discharge for the duration of the test. Water levels (draw-down) should be recorded from the start of the test until the pump is stopped. The recovery of the water level in the borehole should then be recorded until the borehole has recovered to within 10% of the initial static water level.

Boreholes that are to be used every day and must supply a dependable daily water supply, for instance municipal, industrial or irrigation holes, should be test-pumped for longer periods of time. The test pumping should consist of a step draw-down test and a recovery test. This should be followed by a constant discharge test of at least 48 hours and a recovery measurement to within 5% of the original static water level.

Borehole Interference

Should two boreholes be situated close together, it is advisable to record the level in the borehole not being pumped (observation hole) while pumping the other hole. Should the borehole exhibit interference, the water level in the observation hole will decline.

This means that the boreholes are hydraulically connected and pumping from one hole affect the other. Consequently, if the two boreholes are to be pumped simultaneously they will have to be pumped at a rate lower than the tested rate to allow for the interference.

Water Samples

Towards the end of the pumping test a groundwater sample should be taken to determine the quality of the groundwater in terms of its intended use.

The depth of the fracture, along with the safe yield of the borehole and the pressure required by the end-user, are the three most important factors that the installer will have to consider on choosing the correct pump for the customer’s needs.

Boreline®

Yield tests are numerous and continuous and require the frequent installation and removal of pumps and pipes. With Boreline®, this process takes no more than a couple of minutes.

Contractors that have used Boreline® agree that the ease and speed of working with this product makes financial sense. The long-life expectancy of Boreline® also ensures years of hassle-free service.

Yield

A much-asked questions is whether or not a borehole will always continue to have the same yield. The answer to this is “No”. The water yield can vary depending on the time of the year, the number of new boreholes in the vicinity, the yearly changes in the annual rainfall and the local detrimental effects of increased transpiration as a result of the planting of large numbers of trees.

It is for these reasons that wide safety margins are allowed when installing the correct pumping system. Therefore, unless the borehole very obviously yields far more than the end-user needs and the water has also come clear during the flushing process, always insist on having the safe water yield determined for your borehole. An estimate of the water yield by the driller is not sufficient and can be inaccurate.

If you are lucky enough to have a borehole that yields plenty of water, do not pump more than you need.

Groundwater is a very precious resource and should not be wasted.

Mine Dewatering

Existing pump technologies are being applied in innovative new ways in an attempt to dramatically reduce the long and short term costs of dewatering mines.

The pump industry has been experiencing an increase in the demand for dewatering pump technologies, as low commodity prices have convinced mining houses to exploit the reserves of marginal mines.

A large number of existing mines are being refurbished, and the dewatering of these mines is playing an integral part in the reconstruction process of those marginal mining activities. Submersible turbine pumps have emerged as a viable, cost-effective alternative to a dewatering application.

Traditionally, pumping stations were built underground near flooded areas of the mine. These required flameproof motors that were flooded every time there was a heavy rainfall. The identification of heavy-duty submersible pumps to dewater mines as an alternative to the former pumping stations, has become a reality and is a viable option for mining houses.

These submersible dewatering pumping systems are easy to install and are considerably more cost-effective as the need to build pumping stations underground is totally eliminated. As the pumps are submerged, there is no requirement for a flameproof system resulting in further cost savings. This system also provides access to areas that were previously inaccessible and which can now be mined as soon as all the water has been pumped out.

Used in conjunction with Boreline®, this system is further enhanced by eliminating the need to transport and install cumbersome steel pipe. Boreline® is available in continuous lengths and rolls flat. The result is that a 200m (660ft) length can simply be transported in the back of a pick-up truck.

The quality of mine water varies considerably between mines, however, due to the aggressive properties of the water and extreme pH levels, pumps and pipes need to be constructed of corrosive resistant materials. Boreline® is ideal in these situations as the product is corrosion resistant even at extreme pH levels.

Users benefit when dewatering with submersible pumps and Boreline® as this eliminates the need for construction teams to build pumping stations at every dewatering point. Boreline® also results in less maintenance costs over the life of the product, less heavy equipment to install and retrieve and a lower stockholding of pumps and pipes for the mines.

Due to the easy transportability of this dewatering system, mines have responded by utilising emergency stand-by rigs that can be deployed to an area for immediate pumping. Response time is greatly reduced as any length can be installed within minutes.

As pressure continues to increase on input costs and efficiencies, mines are open to innovative ideas and technologies that will keep these operating costs under control in the long term.

Boreline® – you know it makes sense.

Renewable Energy Solutions

As the world’s population increases, so does the demand for energy. Using conventional methods to generate energy means the continuous use fossil fuel reserves resulting in increased emissions of greenhouse gasses, which result in further damage to the environment.

Renewable Energy is the energy use of sun, wind and running water to generate this much-needed energy. This energy can be used to generate light or heat used for domestic or commercial reasons but can also be used to drive a submersible pump which can deliver water.

Windmills were originally very popular where water was needed and power was not available, and were a solution to renewable energy. When compared to solar pumping, windmills are however more difficult and expensive to install due to their bulky nature. Over their lifetime they need constant maintenance which result in higher lifetime costs.

An advantage of using Boreline® is its long-term maintenance-free capabilities which are aligned with those of solar pumping. Boreline® rolls flat which makes it easy to handle and transport to the remote sites so ideal for solar pumping. Once operational, the product can be left as long as the pump is functional. No corrosion or internal scaling occurs and when the pump has to be removed for servicing, this is a very simple operation.

The table below can give an indication of the long term and short term benefits associated with solar pumping and the use of Boreline®. The factors mentioned are a general explanation and are dependent on many different issues.