Articles & Case Studies

Wireless water reservoir monitoring

Posted: Thursday 27th March 2014

In arid Namibia, farms depend on water pumped from underground aquifers into surface reservoir holding tanks where it can then be distributed for the wellbeing of livestock and humans.

Given the large, rural nature of many farms in the region, landowners often have to rely on unskilled staff to monitor and control this key aspect of running an estate. This was the challenge facing Aloegrove, a safari lodge and cattle farm located close to Otjiwarongo, South East of the famed Etosha National Park.

Land owner, Johan Doman, demanded a high degree of confidence that ‘all is well’ at the borehole reservoir and outlying game waterholes. This was requiring staff to visit the borehole three times per week to monitor water levels or provide necessary maintenance.

The solution:

Doman commissioned Wood & Douglas, and Namibian-based, Desert Technical Solutions (DTS), to design and install remote electronic monitoring that would provide a flexible, reliable and cost effective resolution to maintaining Aloegrove’s rural water supplies.

Aloegrove’s single borehole and open top reservoir required an ultrasonic sensor be installed to provide continuous readings of the water level. This still however left the problem of a lack of GSM coverage or presence of AC power at the borehole.

With no GSM coverage at the borehole site direct alarm signalling to a mobile phone is not practical. Wood & Douglas therefore installed a local radio network from the borehole to the base station located at the lodge 6.4km away which does have good GSM coverage. Data is transmitted between the borehole and the lodge, using Wood & Douglas Orion modems, and as this link to the lodge is in the 450MHz range it does not require clear line of sight.

AC power at the reservoir is provisioned by a 12V DC solar based battery system, with additional circuitry provided by Wood & Douglas to reduce the standby power consumption of the monitoring electronics and radio. All this hardware has been housed in a rugged IP66 rated enclosure, important at Aloegrove where the local baboon troop can be destructive. To minimise power consumption from the solar supply, the outstation only reports once per hour to the base station. This status message sent via the UHF radio link gives the current water level in the storage tank as a percentage value and also reports the solar battery status.

The base station listens to the outstation message and interprets the data which is displayed for the lodge staff. If the outstation sends a water level status message below a user preset alert trip level, or sees a low outstation solar supply or misses the hourly report message, the base station sends out a warning cell phone text message to the land owner allowing the problem to be immediately actioned.

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