Before purchasing land in Costilla County, check with the Colorado Division of Water Resources in Alamosa.<personal data hidden> Some areas of Costilla County have had the water sold off the land and you cannot drill any type of well. You would have to haul water for household use as well as any outside water.

If you find you can have a domestic well, that will allow you to irrigate up to one acre of ground and have water for inside a dwelling. An "Inhouse Use Only" well will not allow you to irrigate anything outside. You can't even wash your car.

Much of the soil in the San Luis Valley has a pH of over 8.0. You should get the soil pH checked before planting any trees. You want them to have a chance at surviving. Look in the area for any existing trees. Those are species most likely to survive.

As for trees to plant, find out the depth to the water table. If it is within a few feet of the soil surface, you can plant trees that will accept a high water table such as narrowleaf cottonwood, green ash, hackberry, or siberian elm for deciduous trees. For evergreen trees, you can consider western redcedar, rocky mountain juniper, or ponderosa pine.

I am attaching a list of trees recommended for the San Luis Valley by the Colorado State Forest Service.
After looking over the tree list, if you have questions get in touch with me or the Colorado State Forest Service in Alamosa at<personal data hidden>

Good luck,

Marvin