Barometric pressure fluctuations can significantly distort water level measurements. A project in Namibia demonstrates how modern pressure sensors and the analysis of barometric efficiency (BE) and response function (BRF) help obtain accurate groundwater data.
Located in the southeastern part of the Otavi Plateau in Northern Namibia is one of the country's most significant karst aquifers. An international research team deployed four level probes over ten months to better understand the water level dynamics.
Piezometry revealed a main recharge zone in the topographically highest area. Precipitation infiltrates here, feeding the karst system, which drains in various directions through fractures and cavities. A measurement campaign with four transducers was conducted at Harasib Farm.
Using BETCO software, raw data were corrected for barometric influences. The result: a clearer representation of actual groundwater movement. The barometric efficiency initially ranged from 0.55 to 0.61 and decreased over time.
The barometric response function (BRF) describes how water levels adjust to sudden pressure changes. Notably, Dragon’s Breath and Harasib Lake show similar curves — indicating hydraulic connection and an unstressed system with double porosity.
Hourly water level data showed cyclic fluctuations in a 10–12-hour rhythm caused by tidal forces, which alter pore volume and induce pressure variations in the groundwater.
The data collected from the Otavi karst vividly demonstrate how atmospheric pressure and earth tides influence groundwater level interpretation. Correcting for barometric effects significantly improved data quality. The study confirmed the presence of a deep, unstressed, and well-permeable aquifer with a rapid response to rainfall events. Modern pressure transducers like those from STS provide reliable long-term monitoring even under challenging conditions.