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Farmers’ rainfall data - a valuable resource for studying changing trends in climate
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As the debate on climate change continues and more research is being done in this field, increased emphasis is placed on the value of long-term climate data records. Farmers’ rainfall data can prove highly valuable for studying the changing trends in climate.
South Africa has a very variable rainfall regime across the country - some areas are clearly seasonal (both summer and winter rainfall), some are aseasonal (can expect rain at any time of the year) and in the far north-west of the country there are very arid areas that receive only a small amount of rain each year. Not only is there a huge variability in rainfall across the country, in some regions where thunderstorms can produce the majority of the rainfall, the rain events can be very isolated.
Understanding climate trends
In order to understand the climate trends and the magnitude of variability, a comprehensive network of data is required. However, there is a limit to the availability of long-term climate data from formal weather monitoring sites. Although there is a wide network of weather monitoring stations there will always be gaps, particularly in the rural areas.
Agriculture is one of the main industries within South Africa, and no matter what type of farming is done (dairy, crop, wine, etc.), it will be heavily dependent on the annual climate. For this reason, many farmers collect and preserve very detailed accounts of the rainfall over the years. With many farming operations being family owned and having passed through generations, in some cases extensive rainfall records exist.
Your data can aid research
These data can be very valuable for scientific purposes, not only for uncovering trends in rainfall and understanding how isolated the rainfall is, but also to validate the data collected at formal monitoring sites. In any data management process, errors can and do creep into the data.
An example of the value of farmers’ data in the validation process came from the Agulhas region.
The long-term data record from a formal station showed a period of very high rainfall during the 1950s. While none of the single day records were clear errors, the cumulative figures during this time were hard to believe, but we had no concrete proof that they were erroneous.
When we managed to obtain a long-term record of the rainfall from a farmer in the region, we found that while there was above average rainfall in this region during this period, it was nowhere near as extreme as the formal station data suggested.
This allowed us to confirm that the extreme events were in fact invalid and the data analysis could continue rather using the farmer’s data to study the trends in that region.
Farmers rally to provide data
In June 2012, an article was published in the Landbouweekblad magazine requesting farmers to submit their rainfall records to SAEON. Since then a steady trickle of data has come in, with some records being beautifully hand-written by the farmers themselves.
It has been a very rewarding process to work with these farmers, and some of the stories, as well as the passion that these families have put into collecting the data is amazing. In many cases the way the data have been collected is linked to the farm history and how the farm has been passed down the generations. In one case where a farm had to be sold, the family felt that archiving their rainfall data was actually going to preserve their legacy on the farm.
Records have been received from a variety of areas, including Prieska in the Northern Cape, Theunissen in the Free State, Port Elizabeth in the Eastern Cape, Paarl in the Western Cape and others in between.
The format in which the data have been received also varies, with some farmers keeping electronic records, others faxing through the information, SAEON collecting and scanning a handwritten book of records, and one farmer using “snail mail” to send through hand-written annual records.
All of these records are now available electronically via the SAEON Metacat Data repository and are freely downloadable.
Data recorded to date include:
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While the response from farmers has been really encouraging, far more data records are still required to build up this repository and increase the value of the "Farmer Rainfall Data Campaign".
Anyone with rainfall records, no matter how short or long; daily, monthly or annual are encouraged to archive their data with SAEON. For further information, please contact Victoria Goodall , Data Scientist at SAEON’s Fynbos Node (Tel 021-799 8745).
