A water feature needs to be integrated into the landscape plan for the location. A well planned water feature will look like it is part of the natural environment. In addition to ensuring the design is appropriate we need to have a constant water source, electricity and drainage as part of the feature. Water features will see varying rates of evaporation depending on the size, type of flow and climate they are exposed to. In our climate water features will generally lose 1" of water a week in hotter months (July - August) evaporation may be as much as 3" a week. In addition to evaporation you will need to circulate the water in your feature continuously. This circulation is required to to keep your water feature healthy. One fo the things to be aware of that heavy rains can overfill your pond and you should have a path or overflow pipe from your water feature to divert excess water to place where it will not cause damage.
A water feature is an ecosystem just like a lake or a stream but on a smaller scale. Nature has taken thousands of years to create balanced ecosystems and our water feature is going to needs some help to become a well functioning eco-system. Our water feature needs to ciruculate as mentioned above but we will also need to regular remove debris from the pond. We can do this with a skimmer or skimming net. We will need to ensure we have healthy bacteria to ensure the pond breaks down its waste and add nutrients back into the ecosystem. These bacteria live on surface in the water so it is important your pond has rocks and gravel to provide surfaces for the bacteria to attach to.
There is a lot more to learn about water features. One of our main suppliers has an excellent online Academy. Visit Aquascape Academy for more info.