Adelaide region. The largest are the Torrens and Onkaparinga catchments. Adelaide relies on its many reservoirs for water supply with the Happy Valley Reservoir supplying around 40% and the much larger Mount Bold Reservoir 10% of Adelaide's domestic requirements respectively. Geology Adelaide and its surrounding area is one of the most seismically active regions in Australia. On 1 March 1954 at 3:40 am Adelaide experienced its largest recorded earthquake to date, with the epicentre 12 km from the city centre at Darlington, and a reported magnitude of 5.6. There have been smaller earthquakes in 2010, 2011, 2014, 2017, and 2018. The uplands of the Adelaide Hills, part of the southern Mount Lofty Ranges to the east of Adelaide, are defined on their western side by a number of arcuate faults (the Para, Eden, Clarendon and Willunga Faults), and consist of rocks such as siltstone, dolomite and quartzite, dating from the Neoproterozoic to the middle Cambrian, laid down in the Adelaide Rift Complex, the oldest part of the Adelaide Superbasin. Most of the Adelaide metropolitan area lies in the downthrown St Vincent Basin and its embayments, including the Adelaide Plains Sub-basin, and the Golden Grove, Noarlunga and Willunga Embayments. These basins contain deposits of Tertiary marine and non-marine sands and limestones, which form important aquifers. These deposits are overlain by Quaternary alluvial fans and piedmont slope deposits, derived from erosion of the uplands, consisting of sands, clays and gravels, interfingering to the west with transgressive Pleistocene to Holocene marine sands and coastal sediments of the shoreline of Gulf St Vincent. Urban layout Adelaide is a planned city, designed by the first Surveyor-General of South Australia, Colonel William Light. His plan, sometimes referred to as "Light's Vision" (also the name of a statue of him on Montefiore Hill), arranged Adelaide in a grid, with five squares in the Adelaide city centre and a ring of parks, known as the Adelaide Parklands, surrounding it. Light's selection of the location for the city was initially unpopular with the early settlers, as well as South Australia's first governor, John Hindmarsh, due to its distance from the harbour at Port Adelaide, and the lack of fresh water there. Light successfully persisted with his choice of location against this initial opposition. Recent evidence suggests that Light worked closely with George Kingston as well as a team of men to set out Adelaide, using various templates for city