**Author details**

Shaun Williams National Institute of Water and Atmospheric Research (NIWA), Christchurch, New Zealand

\*Address all correspondence to: shaun.williams@niwa.co.nz

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
