After a very short time the water level in the borehole reaches a preset level (i.e. 15 cm or more above the bottom), at which time the out-flow rate from the permeameter (the volume of water entering the soil around the borehole) decreases, and over time approaches a constant value.
Once the outflow rate from the permeameter has reached a constant value, the volume of water entering the soil around the borehole is determined from the known inside crosssectional area of the permeameter, and the decrease in water level inside the permeameter with time. The water level inside the permeameter is measured at ground surface with a handheld, digital manometer connected with plastic tubing to the top of the permeameter inside the borehole. It can also be measured with a pressure transducer connected with plastic tubing to the top of the permeameter. Connecting the pressure transducer to a datalogger allows for automated measurement of the hydraulic conductivity.
Used for determination of subsurface, saturated soil hydraulic conductivity.
Collects data from different soil depths, between 0 to 20 m below ground.
Manual data collection at ground surface using a digital manometer.
Automated data collection at ground surface with a datalogger.
Volume of water needed is low.
Permeameter can be refilled from ground surface while situated at the bottom of the borehole.
Simultaneous data collection from several permeameters with one datalogger.
Made of strong polycarbonate and acrylic materials.
Compact and light weight.
Comes with digital manometer, and necessary tubing and connectors.
After each experiment, the water level with time data is down loaded to an excel spreadsheet which is used to compute the outflow rate. Next the outflow rate is plotted versus time. The slope of the outflow rate versus time relationship is determined at the point where the outflow rate has reached a nearly constant value. The slope value is then entered in the equation to calculate the saturated hydraulic conductivity. All of this can be done in a short spreadsheet program.
To calculate the hydraulic conductivity (K) of the soil, plug in the rate of fall (R). Rate of fall, cm/min, is easily determined by using the digital handheld manometer.
K=C*A*R/(2*pi*H*H)+(C*pi*a*a)+(2*pi*H/(a star))
Inside diameter of permeameter
Outside diameter of permeameter
Length of permeameter
Effective storage volume inside permeameter
