Stu Hamilton (Author, Hydrology Corner Blog) and Martin Doyle (Tasman District Council) contemplating the New Zealand landscape from the perspective of the Old Ghost Road.

Adventures of a Peripatetic Hydrologist – Water Infrastructure & the Environment Conference

Stu Hamilton (Author, Hydrology Corner Blog) and Martin Doyle (Tasman District Council) contemplating the New Zealand landscape from the perspective of the Old Ghost Road.

Ray Maynard calls me a peripatetic hydrologist.

I had to look it up. There are two meanings: 1) a person who travels from place to place or 2) an Aristotelian philosopher. I think I fit both definitions. Aristotle placed great emphasis on direct observation of nature and that theory must follow fact. I also travel a lot. Whereas I can’t deny this label, I have to wonder if it was meant as a compliment. After all, hydrology is a place-based, observational, science. How can I be a real hydrologist if I am traveling all the time, and hence, not occupied with making direct observations at a place?

My travels from place to place do allow me to learn about what other people are observing and the theories that these observations are advancing.

Most recently this took me to Queenstown New Zealand for the Water Infrastructure and the Environment Conference co-hosted by the New Zealand Hydrological Society, Engineers Australia, and the IPENZ River Group. This conference was sandwiched in between the WMO International Hydrometry Workshop and a three day mountain bike ride on the Old Ghost Road with my son and three hydrographers from the Tasman District Council.

The combination of conference and recreation was very effective.

The hydrology of this region is concealed behind the variety and density of the forests, the steepness of the hillslopes, the imperviousness of the soils, the drainage density, the diversity of geology, and the instability of the landscape. All of these factors become a part of your life, either as impediments or as sources of wonder, as you traverse the landscape slowly on two wheels.

During our ride, at the toe of one steep hill slope with limestone surroundings we found a spring with a resurgence flow that we estimated at 15 m3/s. This is an order of magnitude larger than any spring I had ever seen and quite possibly the largest spring in New Zealand. I am sure most people ride right by this feature, but with 4 hydrographers in our group we aren’t most people. This point source 1st order stream was the size of many 3rd or 4th order streams in other parts of the world. The role of groundwater hydrology can’t be ignored in this region.

The conference organizers did a wonderful thing.

They created a special, ad hoc, session on the Kaikoura Earthquake. This was not on the program because the earthquake had not occurred at the time the program was published. Seeing as no one would have had time to prepare papers or presentations, they simply invited anyone with pictures or data to meet to share the experience.

This informal approach for sharing, and discussing, preliminary observations was very effective. So effective that given the increasing frequency of extraordinary events, I would encourage all hydrology conference organizers to leave some flex in their scheduling to encourage timely sharing of observations of current events.

Most of the information sharing about the Kaikoura earthquake was from groundwater wells. The groundwater level response was diverse and apparently dependent on many factors. In some cases there were transient spikes that either quickly or slowly resolved to near-normal conditions. In other cases there were step changes, either up or down, at a scale of meters. In yet other cases there was little to no response. One of the key differentiators in response appears to be the compressibility of the aquifer.

Abrupt, possibly permanent, changes in groundwater level are not just an academic matter. The use of groundwater to support agriculture has added substantially to the New Zealand economy in recent decades. The consents to take groundwater are, at least in some cases, based on water level thresholds that may have been painfully negotiated through stakeholder consultation to determine the limits of sustainability. It is possible that some farmers are now subject to unreasonable restrictions whereas others may have been gifted with additional apparent water because of soil compression. It could take years to sort this out.

The Kaikoura earthquake also resulted in very many landslides up and down the northeast coast of the South Island. Small and large tributaries have been dammed by landslide debris, but for the most part, there had not been sufficient rainfall for these dams to fill and breach by the time of the conference. There was lively discussion about the threat levels from these dams. I am quite sure that the extent of land disturbance was more than enough that a significant storage and release signature will become apparent in the analysis of affected surface water data.

As a peripatetic hydrologist in the Aristotelian sense, I enjoy learning from the New Zealanders who are deeply invested in their systems for direct observations of nature.

As a peripatetic hydrologist in the traveling sense, there are few places in the world where the influences of geology and weather on hydrological response are more transparent than in New Zealand. An internship in New Zealand should be a rite of passage that every young hydrologist and hydrographer aspires to.

Photo Credit: Ian Hamilton

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