A hydraulic test device for free-flowing artesian boreholes with a case study in Table Mountain Group (TMG) aquifers, South Africa

Abstract

Accurate parameter estimation for aquifers is very challenging, particularly for artesian aquifers in which the potentiometric surface is above ground level. A common approach to parameter estimation for artesian aquifers is to make use of free-flowing and recovery tests. However, such aquifer tests on artesian boreholes are seldom carried out due to lack of an appropriate device readily available for data collection. This paper describes a hydraulic test device for recording flow rate, pressure, EC and pH measurements using an ultrasonic flowmeter, pressure transmitter, EC and pH meters. A procedure to set up the device in the field is outlined. To test the device, an artesian borehole in the Table Mountain Group (TMG) aquifers of South Africa was chosen as a case study, where the device was applied to measure and record flow rate and pressure of the aquifer, as well as EC and pH. Compared with previous free-flowing test data measured manually, the flow data captured by the device was accurate and reliable, and can be utilised to estimate the hydraulic properties of an artesian aquifer. The advantages and disadvantages of the device are discussed, followed by suggestions for improvement. Given that a large number of flowing artesian boreholes are present in the TMG area in which the pressure head of the aquifer is often above ground level, the applicability of the device presented is likely to be widespread. With due improvement of the test device, its wider application in similar conditions, e.g. to artesian holes in the Karoo, would be expected in future.