Branching out - silting up

On 1st July, 1851 two things occurred which changed the face of the Barwon catchment forever. On that date, Victoria was declared a separate colony from New South Wales and gold was discovered at Clunes on Creswick Creek, a tributary of the Lodden River. Five days later, James Esmond arrived in Geelong with samples of the gold found by himself and his two companions. Two days after that, the Geelong Advertiser published the news. By the end of the month, the Victorian gold rush had begun.

The first gold discovery in the Barwon catchment occurred only weeks after the initial discovery at Clunes on 8th August.

Information board near the site of Hiscock's first gold
discovery, situated roughly opposite the Buninyong Cemetery.

On that day, Thomas Hiscock - a blacksmith who had migrated from England ten years before - discovered gold in a gully which now bears his name, in the Buninyong Ranges west of the town.
Like the many creeks and gullies in the area, Hiscock's Gully ultimately drains into the Yarrowee/Leigh River and empties into the Barwon River at Inverleigh.

A memorial erected some distance to the east of the above
sign and which commemorates Hiscock's discovery

Ten days later, gold was also discovered at Poverty Point, Ballarat, on the banks of Canadian Creek only a few hundred metres from its confluence with the Yarrowee River. Within a matter of months around 20,000 hopeful prospectors had flocked to the region to work the easily accessible alluvial deposits.

Sign describing the first Ballarat gold discovery and
subsequent events

This initial rush was followed in subsequent years by the arrival of the big mining companies with the heavy equipment used to mine the deeper quartz reefs of the district. This saw excavation along the Leigh/Yarrowee, extend downstream past Garibaldi to the Leigh Grand Junction and beyond. 

The impact on the river and the creeks and gullies which flow into it was profound. The initial alluvial mining saw a significant reduction in the native vegetation as trees were cleared to make way for mining exploits or harvested for use in construction of the necessary infrastructure. Across the upper part of the catchment, the miners dug into the banks of the waterways, diverted water flows and turned over the soils of the creeks and river flats of the catchment. As they worked, large piles of discarded timber from felled trees washed downstream, causing logjams and impeding water flow. At the same time tonnes of rock and soil were displaced, leaving huge piles of tailings or mullock heaps littering the landscape.
Consequently, as early as the 1860s, the finer sediments from these deposits began to wash into the waterways and make their way into the Yarrowee River before working their way downstream towards the Barwon. On 29th October, 1869 a correspondent to the Geelong Advertiser wrote that:

For a number of years residents on and near the banks of the [Leigh River], and also those on that part of the Barwon below Inverleigh, have quietly looked upon their lands becoming impoverished by the settlement of silt upon them. The effect of the late flood, however, places the matter in a very serious light, and calls for immediate action. Beautiful flats of rich black soil have been converted into beds of clay, and that of the very worst description. Farms that a few years ago would have been suitable for the most exhaustive crops, are now rendered by the accumulation of sludge unfit for the production of grass....The bed of the river is rapidly filling up, consequently such floods must be more frequent and more disastrous.

By 1906 a Sludge Abatement Board had been established to monitor the water quality of rivers and was being called upon to address the complaints of the shires downstream on the Leigh which continued to bear the brunt of the problem. The sludge could be anywhere from about 45 - 180cm thick, with the largest deposits occurring on river bends. As the sediment flowed downstream and filled in pools and hollows, the rate of flow and the volume of the channel would also have decreased.

This image of the Yarrowee Dredging Co mine, 1889 (possibly the Yarrowee
Creek No 1 Gold Dredging Co) shows the degree of deforestation and erosion
caused by mining activity along the river. Image held by the
State Library of Victoria

In recent years, reports commissioned by the Corangamite Catchment Management Authority have confirmed what was evident 150 years ago. Modern understanding of the way vegetation affects hydrology, has also revealed the role deforestation must have played in increasing the quantity and rate at which runoff water entered the river. Today, the silts which were deposited after the beginning of the gold rush are referred to as Post Mining Alluvium and form the surface layer of soil in the area around Shelford and Inverleigh.
Meanwhile over on the Moorabool River, gold was also the order of the day, although the discovery and subsequent mining boom was a little later in coming. Gold was first discovered on the Durdidwarrah property of Augustus von Stieglitz in 1851, however the quantities were not considered workable. Some activity ensued in 1853 when Andrew Love and George Morton discovered alluvial gold on Sutherland's Creek, however, it was not until 1855 when William Hooley and Joseph Davis discovered a gold reef on Sutherland's Creek near Steiglitz that the rush really began.
From 1855 onwards, alluvial gold was extracted at various creeks and gullies along the Moorabool River including Sutherland's Creek, Dolly's Creek, Tea Tree Creek, Mt Doran, the Stony Rises (Elaine) and from the banks of the Moorabool itself at Morrison's however it was not until the 1860s that the large companies moved in and reef mining began in earnest.

The remaining brick footings of the United Albion Mine near Steiglitz

It seems however that the threat of a sludge deluge such as that seen on the Leigh, was not as much of an issue for the Moorabool River. Perhaps this is a reflection of the relatively greater proportion of reef mining in comparison to alluvial activity on the Moorabool.
It is interesting to note that a 2006 report commissioned for the Corangamite Catchment Management Authority showed that despite the greater water flow of the Barwon and the historic issues of increased sedimentation due to mining activities along the Leigh, it is the Moorabool which makes the greatest contribution to sediment deposited downstream at Lake Connewarre. There is no indication that this is related to earlier mining activities, instead it is postulated that the greater overall change in gradient along its length (by comparison with the Barwon and the Leigh) may account for the difference.