Remote Monitoring of Borehole Water Levels

The monitoring of water levels in boreholes in a particular region is important for a water extraction company, as it allows the water extraction to be controlled across the area to keep the water table at a consistent level throughout. However, the widespread and remote nature of these boreholes means that the communication of these water levels can be difficult and costly.

A water industry company in South Africa has combined their radio telemetry systems with Series SBLT2 submersible level transmitters to provide a cost effective and accurate solution.

As the name suggests, boreholes are drilled (or bored) into the ground, and used to monitor the water level and quality. Boreholes used for water extraction are typically completed by installing a vertical pipe or casing to prevent the borehole from caving in and also to prevent surface or rock-borne contamination.

Other applications of the Series SBLT2 include installation in irrigation water canals. Water is pumped from a river into a canal, which can be several kilometers long. At certain points along the way, water is siphoned off to farms. There are radio telemetry stations which monitor the water levels in between these points.

The Dwyer Instruments, Inc. range of submersible level transmitters operates by measuring the hydrostatic pressure at the bottom of the borehole. This pressure is directly proportional to the depth of water. A built-in breather tube allows the sensor to automatically compensate for changes in barometric pressure, and a hydrophobic Teflon filter protects this breather tube from moisture build up.

The hydrostatic pressure is converted to a 4-20 mA signal proportional to a fixed level range. The small diameter of the SBLT2 or the even smaller MBLT is perfect for installation in boreholes. With a maximum cable / breather tube length of well over 200 meters, even the deepest of boreholes can be monitored.

These systems need to be installed in remote regions and be self-powered, usually from solar panels and batteries. The low power consumption (20 mA max) and the simple two-wire connection of the SBLT2 means that the power requirements are kept to a minimum.

These remote locations also require a maintenance-free system. With no float or other moving parts to wear, and no compressors or tubes to clog, the SBLT2 is perfect for this application. The SBLT2 is also unaffected by agitation, condensation, or foam and is easily extracted from the borehole for cleaning or calibration.

Please reach out if you have any questions about submersible level transmitters. The Dwyer team is always happy to assist with any of your needs and can be reached via phone or email.