Packing an umbrella in preparation for fieldwork in a semi arid region may seem a bit strange, particularly when it only rains a few days a year. But I was optimistic; l was hoping for rain in order to see how the landscape and the rivers changed following rainfall. I was visiting the Iluka Jacinth Ambrosia Mine
, located approximately 200km north west of Ceduna in South Australia to undertake a geomorphic assessment of the ephemeral rivers and provide design guidance for the rehabilitation of watercourses that had been removed through the course of mining.
During the first few days of fieldwork we had blue skies, a stunning landscape and lots of very dry rivers. I was struck by the variety and extent of vegetation for an area with such little rainfall. On the last day of fieldwork, the heavens opened and it poured with rain for about 10 minutes and then it rained on and off for the rest of the day. I am pleased to say the umbrella came out and kept me dry while others around me (who had previously scoffed at my umbrella) were drenched!
Storm brewing over the mine site
About 10mm of rain fell that day and it very quickly soaked into the ground with very little runoff. While the rivers didn’t run, the vegetation certainly made the most of it with species such as the fantastically named vagrant lichen unfurling its leaves once rehydrated by rain drops,and the old myall trees soaking up the rain and distributing the moisture to roots 15m below.
Unfurled foliage of the vagrant lichen
Although the rivers didn’t run, a real surprise was finding the rivers we were assessing didn’t discharge into Lake Ifould
as had been assumed by many people before us. A dune lunette that borders the terminal lake prevents river flows from entering the lake and so water seeps into the groundwater table instead. We estimate that in order for the rivers to flow and water to collect at the Lake Ifould lunette, it would require an intense rainfall event for a minimum of 30 minutes. l would love to be there to witness that event but l think l might need to pack more than an umbrella to keep me dry.
Dry river channel characteristic of the region
Making good use of an umbrella with our client (who also had an umbrella handy)!