In with the new, out with the nutrients

As head of water quality research for the ACP, Senior Research Officer Per-Erik Mellander is advancing vital knowledge in how water quality is impacted by agriculture and a changing climate.

Lower Lake, Johnstown Castle Estate

A hydrologist by training, Per-Erik Mellander is far from wet behind the ears. A longstanding interest in environmental systems, and of humans’ place within them, eventually led him to becoming one of the key drivers in Teagasc’s Agricultural Catchments Programme (ACP). He spoke to TResearch about the ongoing work of the ACP, and the importance of a cohesive view of land-use, hydrology and agricultural policy. 

How did you get into this field?

I would say my way into this field was a long one, not a straight one. I did my undergrad in Physical Geography at Uppsala University, Sweden, followed by a Masters in Soil Erosion in Lesotho. My interest was piqued by doing fieldwork, and by beginning to look at the bigger picture of physical geography. I undertook my PhD in Environmental Assessment at the Swedish University of Agricultural Sciences. This was also very field-based, but in a cold climate – lots of snow hydrology. This then led to a greater interest in water quality and working with other forested catchments in northern Sweden. I would say I’ve always had an environmental interest – how we as humans fit into a larger environmental system, into the bigger picture.

What is catchment science?

So, a river catchment can be defined as the ‘endpoint’ for water of a given topographical area – it’s the area of land from which water flows into a river. Catchment science studies a combination of water quality and water quantity within a given catchment area, as well as related topics of soil types, geology, land-use and topography.

The ACP has selected six small catchments, roughly 10km2 each, around Ireland. They were chosen based on them being representative of typical enterprises in Ireland, and on different types of landscapes, in order to give us a representation of the typical enterprises found across Ireland. This allows us to develop a longer-term understanding of the effects of agricultural land-use on water quality.

What are some of the main issues and challenges regarding catchment science?

The main issue is that food production causes pressure on water quality. Producing food needs nitrogen and phosphorus, but if there is loss of these nutrients to water, this impairs water quality. Excess nitrogen and phosphorus in waterways leads to algal growth, which in turn consumes all the oxygen in the water.

The overall challenge is one of how to continue producing food in the most sustainable ways possible. This requires us to understand as much as possible how, where and when nutrients get into water. If you can begin to map those pathways, then there’s further potential for mitigation. It has now become accepted that we need targeted measures to address the goals in improving water quality. Within that field there’s a lot of low-hanging fruit, but we will need much more science in order to understand the underlying processes and be able to reach higher-hanging fruit.

12 May 2023: Per-Erik speaking at Timoleague catchment open day had a theme ‘A Living lab Monitoring Water Quality and Gaseous Emissions’

How has this field developed over time?

In terms of techniques, there’s been lots of development. The key one is near-continuous monitoring, where a sensor is deployed in land or water for automatic data gathering. We have been monitoring these rivers since 2009, and our current monitoring system gives us new information every ten minutes. This numeric data that comes in looks at things like concentration of some nutrients, such as nitrogen and phosphorus. Crucially, automated monitoring helps mitigate data being skewed by only a few sampled points.

Currently, however, there’s no sensor for phosphorus, so this still requires wet chemistry, but we have an automated system for on-site analysis. Overall, though, continuous monitoring makes sure you don’t miss out on any big events and it allows us to better understand how nutrients may be lost to water.

What are the impacts of this topic?

Part of what makes this monitoring so crucial is that it allows you to link water quality to climate issues. This may seem an obvious pairing, but the two topics are often studied at a very different scale – water quality being seen as local versus climate being seen as regional to global. Our monitoring allows a better understanding of both aspects over time, letting you map subtle changes and allowing you to build links more easily between these two issues.

Even though there’s been a focus in this project on water quality, it’s quite multidisciplinary. It touches on agronomic and socio-economic issues, and further physical issues like soil quality and gaseous emissions. So, again, it’s about the bigger picture: looking at the balance and gaining that holistic view of water quality as it pertains to land-use and climate change.

What research have you been doing?

My contribution falls within the remit of the ACP as we’ve discussed it. In particular, I’ve been working on finding a better understanding of nutrient mobilisation and delivery within given pathways to groundwater and rivers, which helps in understanding the effect of land-use on water. By using the high-resolution monitoring, I’ve developed a method for identifying and quantifying losses in different transfer pathways – how much is lost on the surface or below ground, for example. We’ve also developed a way to identify the type of risk of phosphorus pollution in catchments. Much of this work highlights the importance of data collection – these are all developments that have arisen from really exploring the wealth of data we have available.

Can you explain a bit about the ACP’s relationship to policy measures?

Not only does our research try to understand what’s going on within these catchments in order to plan for more efficient measures in future, but it’s also evaluating current measures. Given the level of change we’re dealing with, it’s not always so easy. For example, time lags within a catchment need to be considered. So, what’s monitored in a given catchment could be reflecting the results of a mixture of current measures and measures from several years ago. When trying to gauge the efficiency of policy measures, changes in policy can make it difficult. 

It’s a complex and constantly evolving system, but it shows the importance of our work. All of this research feeds directly into best management practice and helps to shape policy – within agronomics and agriculture, and climate policy.

Can you say a little about the immediate future of the ACP?

Validating current measures and being able to provide that kind of direct feedback – there’s lots of interest in this type of work. It can shape measures to become increasingly efficient and more effective in delivering on policy objectives. The benefits aren’t just at policy level either. There’s interest in how this research can improve management practice.

There’s lots of collaboration within Ireland, for example, Teagasc and the EPA, which is exciting. Something we’re looking to collaborate on further is this type of high-resolution data study of small catchments, allowing us to really understand those subtle shifts within a catchment.

The EPA has a large number of locations throughout the country. However, measurements are done less frequently than at ACP sites, whereas the ACP measurements are much more frequent at a smaller number of locations. Therefore, combining forces there would really provide a much fuller picture.

In general, we aim to understand more and more what role agriculture and future climate will play for water quality. We are starting to see monitoring equipment become more affordable, so hopefully it can become more widespread. We also want to continue and increase our collaborations with other researchers elsewhere and find better ways to improve water quality. 

“The link between water quality and climate science may seem obvious, but the two have often been studied on a very different scale. Our data allows you to link the two more easily.”

Up close and personal

What’s your favourite animal?

Being a Swede, I would have to say the moose. They’re so gracious in the forest, yet so clumsy on hard surfaces. And they always look like they know something we don’t!

If you hadn’t ended up in research, what other job would you have wanted to give a go?

I would have wanted to be a musician. I play the clarinet, mandolin, guitar and flutes. I still make plenty of time to play music recreationally. I love playing it, composing it and listening to it.

What are you most proud of professionally?

In general, I’m proud to contribute to the kind of work that makes a positive difference in the world. More specifically, with the ACP project, I’m glad to assist in the important work of linking climate studies with water quality studies.

[pic credit] Tom O’Connell