NEW PHD ON AGRICULTURAL MANAGEMENT, CLIMATE CHANGE, AND WATER RESOURCES

We congratulate Dr. Hannah Wenng, who received her PhD after a successful defence on 18 November 2021. The title of Hannah’s thesis is “Impacts of Climate and Agricultural Management on Hydrology and Water Quality. A Headwater Catchment Scale Approach.”

In her work, Hannah has studied the connections between agricultural practices, climate, and freshwater environment. She has approached this topic from different angles and on different scales.

First, on a Nordic scale, she contributed to two papers that have (a) discussed the potential impacts of a future Nordic bioeconomy on surface water quality (Marttila et al. 2020); and (b) examined nutrient data from 69 Nordic headwater catchments (de Wit et al. 2020).

Next, she narrowed the scale of her studies to Norwegian conditions, first by examining seven small catchments at different locations of the country, and performing a multi-criteria analysis of, amongst others, trends in the length of the growing season and nitrogen losses (Wenng et al. 2020). Nitrogen losses are receiving increased attention in Norway, especially since the Oslo Fjord has major ecological challenges, and reducing nitrogen loads are therefore of high interest. Hannah found that in catchments with cereal production, the increased growing season length corresponded to a reduction in nitrogen concentrations, but there was no such relationship in grassland catchments.

Hannah doing fieldwork in one of the small Norwegian agricultural streams. Ph: Marianne Bechmann.

Improved understanding of catchment processes was also the focus area of the fourth paper, where she studied two catchments in South-Eastern Norway (Wenng et al. 2021a). Here, she used turbidity sensors as a proxy to understand sources and pathways of sediments, and hence, sediment associated substances such as phosphorus. She studied the way turbidity increased and decreased in storm events and found that the turbidity peak came before the water discharge peak, something that can imply that the sources of both sediments and phosphorus derive from locations close to the river course. This, again, increases our understanding on which environmental measures will have the best effect on water quality.

Her fifth and final paper concentrated on water discharge patterns (Wenng et al. 2021b). Again, she used seven small headwater catchments, but this time she studied the hydrological data, for as she says, if you are to understand how nutrients are transported in a catchment, you need to get the hydrology right. The results revealed different hydrological regimes of rain and snow-dominated catchments. The catchments responded differently to changes due to their location and inherent characteristics. This highlights the importance of studying local hydrological regimes to better understand the effects of climate change, which will be useful for site-specific management planning.

Hannah Wenng’s PhD was funded by the Research Council of Norway, and she has joined BIOWATER since she started in May 2018. Her PhD was shared between NIBIO and NMBU, with supervisors Tore Krogstad (NMBU); Marianne Bechmann and Eva Skarbøvik (NIBIO) and Hannu Marttila (University of Oulu).

Her PhD thesis can be found here.

Papers in her PhD:

Marttila H, Lepistö A, Tolvanen A, Bechmann M, Kyllmar K, Juutinen A, Wenng H, et al. (2020) Potential impacts of a future Nordic bioeconomy on surface water quality. Ambio49 (11), 1722–1735.

De Wit H, Lepistö A, Marttila H, Wenng H, et al. (2020) Land-use dominates climate controls on nitrogen and phosphorus export from managed and natural Nordic headwater catchments. Hydrological Processes 34 (25), 4831-4850.

Wenng H, Bechmann M, Krogstad T, Skarbøvik E (2020) Climate effects on land management and stream nitrogen concentration in small agricultural catchments in Norway. Ambio49 (11), 1747-1758.

Wenng H, Barneveld R, Bechmann M, Marttila H, Krogstad T, Skarbøvik E (2021a) Sediment transport dynamics in small agricultural catchments in a cold climate: A case study from Norway. Agriculture, Ecosystems and Environment 317.

Wenng H, Croghan D, Bechmann M, Marttila H (2021b): Hydrology under change. Long-term annual and seasonal changes in small agricultural catchments in Norway. Hydrology Research.

Feature photo: Marianne Bechmann