Staff Profile - Channa Rajanayaka

What is your area of specialty/role at NIWA?

I am a groundwater modeller with the Hydrology Group in Christchurch. I specialise in developing analytical and numerical models to simulate groundwater flow and contaminant transport within aquifer systems, and also interactions between surface and groundwater. I also have expertise in soil-crop-water balance modelling. I was initially interested in estimation of land surface recharge into groundwater, this has evolved into estimating irrigation water requirements. Several regional councils (e.g. Waikato, Otago and Gisborne) now use our estimation methods for irrigation water allocation. In addition to doing some cool science, I manage the Hydrological Modelling Group at NIWA - I enjoy that role.

What made you made you want to become a groundwater modeller?

When I grew up in a mountain region in Sri Lanka, groundwater was the only source of water for us. As a child it was fun to see springs appear from hill sides and disappear after a few months. So, I have been always fascinated by this ‘invisible’ resource. My first job in Aotearoa-New Zealand was at Lincoln University to help academics who were developing mathematical models to understand contaminant transport mechanisms and attenuation processes in groundwater systems – that job made me want to become a modeller, and to extend the hydrogeological expertise that I already had.   

What’s the most rewarding thing you’ve done in your career so far?

It’s really rewarding to see what I do have an impact by helping people to use water more sustainably. To give a couple of examples, the integrated surface-groundwater model we developed is being used in Motueka near Nelson for water resource management. Waikato Regional Council uses our groundwater model and an approach that we developed to estimate water age distribution to understand the impact of land use change in the upper Waikato catchment. Here at NIWA we recently developed a tool to estimate cumulative catchment streamflow depletion caused by water abstraction. This tool assists regional councils to manage water resources under NPS-FM requirements and perform better water accounting. I also find satisfaction in seeing that irrigation water allocation, which accounts for nearly 80% of our summer water use, can be done more efficiently using our work.

What do you like to do outside of your work at NIWA?

I am a keen tramper and walked all the Great Walks in Aotearoa and many more tracks in North Island, when we lived in Hamilton. However, my main achievement is climbing Kilimanjaro. I also recently got into home brewing which is good fun and starting to produce some impressive results.

Caption: Channa hiking the Milford Track.