Flow rate, static and dynamic water level in the well
Once you have a water well on a country site, you need to understand that this is not a simple hole in the ground. In fact, you have developed your own complex hydraulic structure, which has its own characteristics that should be monitored periodically.
At the same time, you will need to learn what a dynamic water level in a well is and other terms necessary for its uninterrupted operation.
These also include:
- depth;
- debit;
- static depth.
These indicators are recorded by the master after the completion of the drilling of a well and are noted in the basic document - the well passport to the water. In the case of depth and flow rate, everything is more or less clear, but not everyone knows and therefore confuses the question of the static and dynamic horizon for many. Further it will be told in detail about what these numbers are, why they need to be known and how to apply them in practice..
The concept of a static level and its features
The static level or piezometric level refers to the depth in a water well, which is measured from the surface to the water mirror at rest when the pump is off. The indicator is very important and valuable, so even in some areas of the country there is a special monitoring service that measures the static water depth in the observation wells. Data are the basis for keeping records of groundwater reserves.
Usually in sandy shallow wells, the static water level in a well very often coincides with the water table. Often, the owners of such wells ask a question about the location of the water mirror just a meter or two or even flush with the surface.
Does the well from the upper layers of the soil fall into the well? A simple experiment will help in resolving this issue. The following experiment: if pumping water from the well and lowering the water column in the casing does not lower it in the annulus, then there is no overflow.
The coincidence of the water level in the sandy shallow wells with the groundwater horizon occurs because they are hydraulically connected to each other. At the same time, it does not at all mean that the chemical composition of the water in them is the same and all contaminants from the surface directly fall into the well.
Very often, the connection of water pillars is possible in large thickets of natural lakes, river beds and other reservoirs, reservoirs that are “windows” in a waterproof layer. As a result, two horizons unite with each other and the rules of communicating vessels begin to operate, when the mirror in the well almost coincides with the nearby reservoir.
Of course, backwater is also possible, in which the water column is artificially increased, for example, because of the terrain, but this is extremely rare.
The concept of the dynamic level and its features
The dynamic level is the horizon of the water mirror, which is obtained when the pump is running. It is also measured in meters from the ground surface and is usually marked on the well passport.
It should be noted that each pump will have its own dynamic well level, which in most cases differs from the others and depends on the performance.
It is also an important indicator and should be known in order to choose the optimal height for hanging the pump, the price of which can be substantial.
Next, you will learn how to correctly measure the dynamic horizon with a lowered running pump and a pipeline with a cable. (See also the article Which Pump is Better for a Well: Choice Features.)
The principle of operation and adaptation
To do this you need a simple device that you can easily make with your own hands in a few minutes.
The principle is quite simple:
- take a piece of plastic or other plastic tube with a length of 100-150 mm;
- drown its upper end, for example, drive a wooden chopik and twist a screw into it so that you can fix the rope. Also tighten the screws and the entire diameter of the chopik;
- Lower the device into the well on a rope or measuring tape.
Tip: wait for the cotton, which will occur at the moment, as soon as the tube touches the mirror of water.
How to measure
Below is a simple but effective instruction.
- Turn on the pump.
- Lower the tube and rope construction into the well.
- Periodically twitch at a height of 200-300 mm, checking the depth of the water mirror.
- Straighten the rope as needed.
- Notice that the mirror has stopped falling, which means that you have reached the dynamic level for this pump.
- Secure the rope.
- Continue to pump out water from the well for another 30-60 minutes, periodically checking the depth of the water mirror.
When the horizon descends slightly or does not descend at all, consider that the dynamic depth has been established. Lift the rope and measure its length, which was submerged well, to determine it for a water source.
Why do you need it
When you have determined the dynamic and static level of the well and know the performance of the pump, you can easily calculate its flow rate. For example, if the pump has a capacity of 1 m3/ hour the difference between them is 5 m, and the water column is 16-18 m, the actual well flow rate will be 3 m3/ hour (16/5) or 200 l / meter, which is called the specific flow rate.
Tip: do not lower the dynamic horizon below 2/3 of the total height of the water column of the well.
When calculating the size of water pillars, keep in mind that they cannot be considered permanent. They fluctuate from season to season, for example, the static depth drops in the dry season.
Conclusion
Knowledge of the flow rate, static and dynamic levels of the well allows you to perform the necessary calculations for its uninterrupted operation. In the presented video in this article you will find additional information on this topic.