The first thing to consider when building a pond is location. Lots of debate in this area, but I wanted to share my thoughts. The first thing to consider when building a pond is how far away to put it.
The hope is that you will be going out every day to spend time with your Koi. They love attention and they love to be fed. You will want to be able to monitor not just your Koi, but ensure that they are happy and healthy.
My recommendation is to keep the Koi close to your back door OR easy to get to. If you have to hike to the pond or navigate a path to get there, the journey may become a chore if you are traveling it several times a day.
The next thing to consider is having enough room for the pond and the filter equipment (or at least have a plan as to where the filtration should go). Its always good to think about the foot print you want for your pond and make sure its got the room it needs, with some extra for growth. Trust me, you will want to grow out your pond either by adding plants OR expanding your filtration. Its best to make sure the location you pick isn't too small - look for a spot that gives some extra room to grow.
Next thing, you might want to consider the seasonal changes for the location. Koi can get sun-burned (especially Kohakus and light colored Koi) so you need to plan for a way to provide shade from the UV rays. A high wind area or places of intense heat will cause the water to evaporate faster so its good to be aware of how the environment will impact your pond. You might want to also consider what the location is like in the other seasons including spring & winter - see if the location is notorious for snow drifts or its frequently flooded during a hard spring rain. Its also important to note that these issues don't necessarily make a location bad or good, but it does mean you will want to plan to address these potentials issues in your overall design (more to come on how to work around these issues).
Another thing to consider is what predators will be after your Koi. Koi are considered quite the catch to raccoons, bears, and herons. Colorado happens to fall into the migratory path for the herons, so it's important to think about whether the location makes it easier or harder for predators to get at your pond. (Again, will have more ideas about how to ensure your Koi pond is predator proof).
Finally, take some time sitting at the location you choose and just observe. Choosing the location of your Koi pond is all about making sure you can enjoy your Koi. You may find that the best viewing spot for the pond will face your neighbor's bathroom window (yeah - I got that!). You may find that the view forces you to see a part of the yard that is messy or you see your neighbors junky car or swingset. Take the time before you start building to be happy with the location.
Location is everything!
Happy to hear from others what they recommend when selecting a location.