The cache is of a small size; however there is no room for swaps or trackables, and the log may be difficult to extract. PLEASE DO NOT remove the cache from its position ... just lift out the log and then replace in the same way. Bring your own pen and please handle the cache with care in extraction, and replace it exactly as you found it. The cache is not located in the stonework, so there is no need to lift or remove any of the original stones. Please respect the sensitive ecology of the area, and tread with care.
"High Water Mark”
Probably no statement about South Australia has been given wider currency that its claim to be the driest State in the driest continent. Only 3.3% of the land area receives a mean annual rainfall above 500 mm, while about 83% receives less than 250 mm. There is very little runoff within the State and the most important source of supply is the River Murray, which originates from head-water sources outside the State.
The Thorndon Park Reservoir was constructed over the years 1857 to 1860 and was the first storage reservoir for Adelaide’s water supply. The Reservoir was constructed to hold water diverted from the River Torrens. The type of construction is of compacted earth with an alluvial clay core sourced entirely from inside the reservoir area. The clay core was watered, hand rammed and trodden by bullocks in an attempt to achieve maximum compaction. The total cost of the completed works was £223,000. The original capacity was 138 million gallons; this was increased in1864 to142 million gallons.
Piped water under pressure was first supplied to some streets in Adelaide on 28 December 1860, the 24th Anniversary of the Proclamation of South Australia (Proclamation Day). The cost of water from Thorndon Park at 3.8c per kilolitre competed favourably, with that charged previously by the water carters of between 65c and 90c per kilolitre.
The Reservoir was decommissioned in 1977 and dedicated as a recreational reserve. In 2001 an irrigation pipe burst, flooding the outlet tunnel and undermining a section of the embankment. The reservoir was then drained to allow further investigation and subsequent repair works and augmentation.
The original Reservoir stone wall embankment on the southern side still exists today. The stone walling embankment was "pitch-paved" and each stone was individually hand laid. You can still see the “High Water Mark” of a time when the Reservoir was once at its capacity. This mark is distinguished by the distinct discolourations of the stone work.
This cache is placed in the vicinity of a section of the original stone wall embankment where you can inspect the “High Water Mark”.