As of Ubuntu 12.10, subversion 1.7 is available as part of the distribution. Subversion can be installed using apt-get.
sudo apt-get subversion
For earlier version of Ubuntu, there is a ppa available at subversion-1.7. The repository can be added as follows:
sudo apt-add-repository ppa:dominik-stadler/subversion-1.7
To get the latest version of subversion update and upgrade the repository.
sudo apt-get update
sudo apt-get upgrade
I needed to also do a dist-upgrade.
sudo apt-get dist-upgrade
I'm assuming that you already have subversion installed, if not:
sudo apt-get install subversion