The key to making your waterfall look natural, is to be sure to remove plenty of dirt and recessing the waterfall into the ground. Many people make the mistake of constructing it above the natural grade level of the original grade. Rocks do not look natural sticking above the surface of the ground. This is especially true if the waterfall rocks are the only ones visible on the bank, hill or grade where the waterfall is located. The rocks of the waterfall should give the appearance that, over the years, water has washed down the hill or bank, eroding away the original surface soil and exposing the rocks hidden beneath.
The next step is to apply the 3/8″ rebar 8 to 10 inches on center, criss-crossing each other, and fastening them together in a grid using a tie wire to fasten them together. Small 2″ x 2″ blocks called dobies are then placed under the grid to hold above the dirt. When concrete is applied, it must completely surround all the rebar. No rebar can be touching the soil or it will rust. And rust, like cancer, will spread and follow the rebar into the concrete structure. As the rebar rusts it swells, much like would when it gets moisture in it. The swollen rebar hydrologically causes the concrete to crack.
Use flexible PVC pipe, not rigid pipe, because it is easy to manipulate around the corners and over uneven ground. But most of all, by using flex you will eliminate the need for fittings such as elbows and couplings under ground, thus eliminating possible future sources of leaks.
You can install the flex under the rebar or alongside it, down the waterfall’s course. One of the major flaws with liner constructed pondless waterfalls is that they use sump pumps which suck energy (60% more than centrifugal pumps). They then fill the cistern containing the pump with gravel, reducing the available water space. Consequently, when the waterfall is started up, most of the catch basin or cistern is drained of water before the previously pumped water can return to the basin. This makes it necessary to regularly add water to the basin or the pump will run dry and burn up. It is very important to add a reliable water leveler to a pondless waterfall since you are not able to see the level of water in the catch basin.
In concrete construction, anti-vortex suction drains (just like what is used in swimming pools) can be installed in the bottom of the basin. Galvanized grating can then be spanned across the basin and rock placed on top of the grating to hide it.
Now the basin is empty and free of gravel to allow plenty of room for water storage. An out-of-pond, high-efficiency centrifugal pump can be used to circulate the water. Unlike sump pumps that are used in liner construction, a centrifugal pump uses 60% less energy, is easy to maintain, carries three times the warranty, has four to five times the life expectancy, and there is no need ever to access the basin or remove stinky, filthy gravel to get to the pump.
Most concrete pumpers know how to apply concrete to waterfall rebar, and they only charge a couple of hundred dollars. Troweling is easy; anyone can do it because it does not need to be smooth. Just knock down the rough edges and smooth with a sponge.
The concrete itself only costs $100-$125 a yard with most pondless waterfalls requiring only 2 to 3 yards. Check out the cost of a liner kit alone (without any labor)! and search the internet under “Pond liners vs. concrete.”
Don’t waste your money on a temporary solution. Reinforced concrete actually cost less and will last decades longer.