Every well owner/operator has a responsibility to monitor the water levels in the well they are using, whether for personal or community use, to comply with State regulations or for scientific monitoring. There are several methods to acquiring this data, each with its own benefit and issues. Providing accurate data with economical and efficient equipment has driven people to search for a better method, hence the sonic technology movement.
Sonic meters monitor levels by sending a low frequency sound pulse into a well which reflects off the water's surface. It then performs a time distance measurement on the reflection to provide a reading in feet and inches. These meters which are available in portable or permanent configurations, mount easily in the vent hole of the well, do not require anything to be lowered into the well and will provide accurate readings in seconds. Sonic meters, such as the Eno Scientific Well Sounder 2010 PRO and Well Watch 670, also include a built in data logger for simple and complete data collection with the ability for long term monitoring and telemetry integration.
People frequently confuse the term 'sonic' with the 'ultrasonic' meters that are also non contact level indicators. These methods are distant cousins in the sound spectrum family. Where the Sonic meters are low frequency, the Ultrasonic meters are very high frequency, similar to a laser beam. The long waves of the Sonic units have the ability to travel around corners, through coils of pipe and around obstructions in the well making them very versatile. The Ultrasonic meters are very directional and require line of sight to the object they will be measuring. Ultrasonic meters are beneficial for measuring short distances where they are not contained, such as tank or open surface water level measurements. The Sonic meters must be contained in a relatively small diameter space, 12” and below, or can be contained in a sounding tube for larger diameter wells.
 |
Another method for taking measurements are water level tapes. These come in a variety of styles and are commonly used for taking measurements of various wells. They are basically a rolled up tape measure with built in conductor wires. When the tape measure hits water the wires are bridged and the tape beeps to alert the user to the presence of water. The issue is that there can be multiple places in a well where water enters the casing and any one of these entrance points can cause the wires to bridge and the tape to beep causing a false reading. Most wells are also outfitted with pumps, wiring, stabilizers, etc and the process of weaving an object down through this equipment can be very difficult. Some wells have only a fraction of an inch of available space to operate in and if the tape gets stuck it has to be cut off and replaced. Not a big deal if you don't mind random tape pieces in your well and the expense of buying a new tape every time this happens (note: water level tape prices vary on length, a 300' tape can cost as much as a Sonic meter that can measure down to 4000') In addition, if the tape is not properly sterilized between wells it can cause cross contamination. The tapes are also only useful for manual readings which can be time consuming depending on the depth to water and there is no data logger so I hope you bring a pen and paper.
Pressure transducers are a submersible method which requires a pressure sensor to be lowered down into the well and left for long term monitoring. The benefit of transducers are the level of accuracy they provide however they are costly and have similar limitations to the level tapes. They need unobstructed space to be lowered into and are not ideal for wells with turbulence. They also store the data internally but do not provide any type of real time display so the data must be downloaded. Transducers are purchased depending upon the custom length you provide. If the water table drops below the set transducer level then you will need to replace it with a longer cable. Products that are submerged for a length of time will eventually corrode and will need to be replaced so be prepared to pull it all back up.
Each method has its benefits but why would you take the risk of lowering an object into your well if you could get the same readings in a fraction of the time without the risk of contamination and lost/broken equipment? This is why people have migrated towards a better, safer and more economically feasible method. Check it out for yourself www.enoscientific.com
