Waterfall

In a swim pond or koi pond, waterfalls are not just for looks or the cool sound of water splashing on rock.  They also filter and aerate the water helping to keep the pond water sparkling clean.  In fact, they are often referred to as "filter falls" or  "biofalls."  I bought an Atlantic BF2600, which is basically a very sturdy plastic tub with a 26" spillway.  It comes with a grate that fits inside several inches above the bottom, two filter pads that rest on the grate, two "media" bags that hold the filter media of your choice and rest on top filter pads, and another grate for the top on which you place rocks to help disguise the waterfall tub.  

Similar to the gravel in the regeneration zone, the filter media will be a home to beneficial bacteria that will convert dissolved nutrients.  I read that lava rock was a good media. Luckily, it is available at Lowes as propane grill briquettes over in the outdoor living department.  Four 7 pound bags seems to make a good layer in my falls.

Water enters the waterfalls through a 2" bulkhead fitting (also included) at the bottom.  As with the skimmer, you drill the hole for the bulkhead fitting depending on which side of the tub is convenient for your set-up.  I put it on the back since the pump will be behind the waterfalls.  Also like the skimmer, the pond liner is attached to the face of the waterfalls to keep the water in the pond where it belongs.  Again, the manufacturer supplies a faceplate, silicone and all the hardware needed.  If the waterfall is to be placed outside of the pond liner, additional liner is used to contain the water in a stream that flows to the pond.  Unlike the skimmer, however, you don't have to use a transit to calculate water levels --  just place the waterfalls on level, firm ground wherever you like.  The only calculation needed is is to figure the head -- if the falls are too high, the head may be so great that your pump may be pumping far less water than what you were counting on.  Most of the pump manufactures' web sites will have information on calculating head and pump outputs at various heads.   

Once the falls are in place, it's time to create.  We started with a heavy layer of the cobble, and then placed a couple of large, flat rocks donated by Brian donated. The one on top was really heavy and had to be placed with some chains and the backhoe.

Water is either stupid or obstinate, and won't necessarily go where you want it to. About half the volume of water falling on to each of the large rocks was running down the backside of the rocks and disappearing into the underlying cobble, greatly decreasing the whole visual effect of a cascading water feature.  To help keep the water moving in the right direction, Atlantic makes an expanding foam which is just like "Great Stuff" except that it is black, making it practically invisible when water is flowing over it.  I used it to set smaller rocks and fill in voids between rocks, and that got all the water spilling down the face of the waterfall.  The photo below shows our initial effort before using the foam. Additionally, the water flowing out of the filterfalls is about half the output of the pump -- the other half is being directed through a 2" pipe into the deep zone so that water does not stagnate there. The photo also shows the pump house and the barrow that will conceal it -- more on that stuff later.