Alluvial Gold Mining or River Gold Mining
We covered some of the basics of alluvial gold mining in Prospecting For Gold that we shall not revisit here. Instead we will look at more techniques of the river gold miner.
Once you have established a good location for mining alluvial gold you want to process as much material as quickly as you can, with as little effort as you can. This is the way to make money from gold mining. If you are happy panning in your spare time just for the experience then you need not read on.
We looked briefly at using sluice boxes for alluvial gold mining. There are different kinds of sluice box set-ups. There is the sluice box that you lay in the flow of the river and use the current of the river to wash the waste material through. You can feed the sluice box by shoveling material into the head of the sluice box, or you can sit the sluice box on the bedrock (the hard rock bottom) if the situation allows and then you can sweep the floor of the river through the sluice box. If you are choosing this method you need to make sure that your sluice box is indeed on the hard rock bottom, and that you make sure that the gold you disturb cannot flow around your sluice box.
In the early days prospectors used water guns or hydraulic monitors to wash the sides of creeks and in some cases whole hill sides down and through a sluice box. They found a water source above where they were working and channeled it through water races and pipes down into the water cannon to achieve high pressures. 
This kind of mining is generally not considered acceptable because of the high impact on the environment. However, there are other tools gold miners can use.
One of the more popular ways to mine rivers of alluvial gold today is the gold dredge. These can vary in size from a backpack unit to great floating barges the size of hotels. If you are considering using a dredge you need to consider factors such as what your permit allows, what your budget can afford both to buy and then to run. You need to consider how deep the hard rock bottom is and how high you will need to suck the gravel, this will affect the size of the pump you require. The size of the of rocks and gravel will affect the size of the nozzle that you need to run. If you are working below the surface you will want to consider the option of a dredge that can pump hot water through your wetsuit. You may also need to consider the access to your claim. Can you get your dredge out of the water easily in the event of flooding?
Where the water flow is not significant enough to run a conventional sluice box or to run a gold dredge, gold miners developed technology such as the High Banker Sluice. These sluice boxes work with a minimal flow and they are able to recycle the water to improve performance. The Trommel is another way of sorting the gravel in an efficient manner when water is restricted. These are advances on the rocker boxes and other gold mining technology used by miners a hundred years ago. They are also just scaled down versions of what the high production commercial miners use.
