Instruments for Measuring Groundwater

Hydrogeology — the science that studies the origin, conditions of occurrence, composition, and patterns of underground water movement. It also studies the interaction of underground waters with rocks, surface waters, and the atmosphere.

All waters of the Earth's crust located below the Earth's surface in rocks in gaseous, liquid, and solid states are considered underground waters. Underground waters are part of the hydrosphere — the water shell of the Earth. Freshwater reserves in the Earth's interior amount to up to 1/3 of the waters of the World Ocean. About 3367 underground water deposits are known in Russia. Less than 50% of them are exploited. Sometimes underground waters cause landslides, waterlogging of territories, soil subsidence, and complicate mining operations in mines. To reduce the inflow of underground waters, drainage of deposits is carried out and water drains are constructed.

Why it is necessary to monitor the groundwater level:

• The dynamics of underground waters is the main basis that allows for the correct calculation of underground water reserves. Hydrodynamic calculations rely on experimental data, i.e., performing test pumping from water intake wells with mandatory monitoring of the rate of level decline over time(i.e., during pumping, a level meter is lowered into the well, and the level change is recorded over several hours or days at a certain frequency). That is why the fieldwork stage at the water intake is mandatory when assessing underground water reserves.
• Changes in groundwater levels cause uneven subsidence of soil masses and pose the greatest danger to buildings and structures.

Why it is necessary to monitor the conductivity and temperature of groundwater:

• Wastewater from enterprises is subject to significant pollution due to the concentration of heavy industry enterprises, a high level of urbanization, and a developed transport network. If such an enterprise makes a discharge, by measuring the water conductivity, we will immediately see a sharp jump and understand that urgent measures need to be taken.
• By measuring temperature, similarly recording a temperature spike, we can unequivocally judge that a discharge was made into the water by unscrupulous enterprises.
• Underground waters are diverse. They differ in composition, temperature, direction and speed of movement, and other characteristics. By conductivity and temperature values, we can obtain data about the source of formation of these underground waters.
• Changes in water temperature during pumping with pumps become immediately visible on graphs, which also allows indirect judgment of the water level, even if the pressure sensor has failed.

To monitor underground waters, we offer comprehensive systems to solve these tasks:

1) Digital level and temperature converters Series 36XW

These devices are ideal for monitoring wells located near the power source and a computer for data reading. We simply receive signals about level and temperature values with the required frequency and high accuracy up to 1 cm. Sensors connect to a PC. The devices come with software. Thus, we can promptly take measurements and record and analyze data online in graphical or tabular formats  (L).

2) Monitoring groundwater level and temperature using autonomous data loggers Series DCX-22

These devices are hydrostatic pressure sensors combined with temperature sensors, lowered to the bottom in one housing together with a data logger and a lithium battery. A special cable with a capillary tube for atmospheric pressure compensation comes to the surface; at the cable exit point, there is a special moisture-proof module for connection.

When using this solution, we need to occasionally come to the equipment installation site and connect to the logger using a special cable to download data to a computer or PDA. These devices also come with convenient software and the ability to configure necessary calculations, whether depth or distance to the water surface.

In addition to the above, Keller is the only manufacturer that produces a solution with two absolute pressure sensors DCX-22AA. Thus, we can use a cable without a capillary tube, and accordingly not worry that it will clog with condensation, dirt, bend, or simply break! This also allows extending the cable if we initially miscalculated the length!

3) Monitoring level, temperature, and conductivity using an autonomous data logger and data transmission via GPRS to email or via (SMS)

See the article for more details Autonomous measurement systems with data transmission via GPRS (GSM-2)

Also read our article about our experience working with these systems in low temperature conditions.