A high elevation weather station and cloud precipitation collector for Jonkershoek

Approaching the site, looking down the Jonkershoek Valley towards Stellenbosch in the distance. (Picture: Abri de Buys) Dr Gavin Bingham touches down in the ZU-RDX with a cargo pod full of equipment and a cloud precipitation collector strapped securely in the passenger seat. (Picture: Abri de Buys) The SAEON team assembles the weather station. (Picture: Genevieve Thompson). View larger version The job done! Complete weather station with cloud precipitation sampler and GPRS communication. (Picture: Abri de Buys) View larger version

The SAEON Fynbos Node’s strategic development of infrastructure and datasets around the 70 year old existing streamflow experiment at Jonkershoek has made a leap forward.

SAEON collaborators and scientists previously involved with Jonkershoek research and monitoring agree that precipitation inputs into the catchments are understudied and not well understood despite a substantial network of rain gauges in the valley. This is particularly the case for more remote, higher elevation areas where there are fewer rain gauges and they are harder to attend to on a regular basis.

A further question related to higher elevation hydrological inputs is what the contribution of cloud or mist precipitation is to the total water input that is measured downstream at the weirs.

After the recent successful construction and testing of a cloud precipitation collector it was time to begin the planning and preparation for a high elevation weather station in Jonkershoek. A site was chosen at 1 214 metres above sea level on top of the mountain at the head of the Jonkershoek Valley. Approval to develop our monitoring infrastructure was granted by Cape Nature, and we were able to proceed in earnest with the next step of our plans.

No ordinary installation

Due to the remoteness of the site and the weight of the equipment, as well as tools and supplies needed to install the station securely for the long term, this was no ordinary installation procedure. It became clear that it would take a superhuman effort to carry all this from the nearest vehicle access point, about five kilometres away and 500 metres below the site.

A decision was thus made to contact the Bateleurs, an organisation of private aircraft owners who volunteer their equipment and skills for environmental causes. The Bateleurs put us in contact with Dr Gavin Bingham, pilot of his own ZU-RDX helicopter.

After the last supplies were bought, the sensors and logger as well as the modem that would relay data back to the office were set up in the office and tested. A team composed of Fynbos Node members volunteered to take part in the field work, which could only be done on a weekend, due to the schedule of our pilot. And so, arrangements were made to meet Gavin at Stellenbosch Airfield. The team left Kirstenbosch Gardens at 06:00 and proceeded to meet Gavin at 07:00 on 3 March 2013.

The aim was to get the equipment moving up the mountain while temperatures remained cool enough for the helicopter to hover at altitude with the extra weight. First up though, we had to transport a member of the team to the site, to help with offloading of equipment that would arrive with subsequent flights. After deploying a flare to check the wind direction, the first of several successful landings was made near the site. Several flights later, all the equipment was on site. This was made to look easy by Gavin’s piloting skills along with the handy cargo pod that attaches between the skids of the ZU-RDX helicopter.

In the meantime, the ground team, who had driven the vehicle to the closest access point and hiked in, arrived on site. With that, we started testing the modem to ensure we would have a strong signal to communicate remotely from the office. We also dug holes, mixed cement, planted masts and started on the final assembly of the weather station while the cement was drying. The last two flights brought up the remaining members of our team who had assisted with the packing and loading of equipment at the airfield and with the assistance of everyone, quick progress was made.

By the time the last passenger was dropped off on site, flying conditions had deteriorated significantly. The aircraft’s ability to hover safely is dependent on the density altitude, which is strongly influenced by temperature. As temperature increases and air becomes less dense, the lift created by the rotor becomes weaker and the aircraft can hover safely with less weight.

However, since we had a back-up vehicle at the nearest road access, we were happy at this point to declare the flying mission a great success. Gavin returned to the Stellenbosch Airfield and we managed to send some tools and packing material back down with him, to lighten the load that the team had to carry down at the end of the day.

With the station assembled, anchored and running, and the sun low in the sky, we decided to call it a day and made our way down the mountain with a sense of accomplishment and a few small outstanding jobs left to do. These were subsequently completed by Abri and Siyasanga Mpehle, Technical Intern at the SAEON Fynbos Node, along with some teething problems that had to be sorted out.

We are happy to report that the weather station installation was a success and that we are able to get real-time data, any time of the day, from our office at Kirstenbosch Gardens.

A big thank you to the Bateleurs, Dr Gavin Bingham and the Fynbos Node team who made this possible.