Mads Steiness, IGN, defends his thesis at Geology Section

Mads Steiness defends his thesis,

“Riparian Lowland Hydrology: Impact on Nitrate Transport at Local scale”

Supervisors:
Professor Peter Engesgaard, IGN
Senior Scientist Anker Lajer Højberg, GEUS

Assessment Committee:
Professor Bjørn Kløve, University of Oulu – Finland
Professor Stefan Krause, University of Birmingham – UK
Associate Professor Majken Zibar (chair), IGN

Summary:
Farmers apply nutrients to their field with chemical fertilizers and animal manure to enhance crop growth and yield. Excess nutrients can be washed out into surface water systems and leach into the groundwater. High levels of nutrients can have severe impacts on aquatic environments causing eutrophication of stream, lakes and coastal systems leading to loss of aquatic biodiversity. Riparian zones are situated along rivers and streams and can serve to mitigate diffuse source pollution of nutrients from agricultural uplands. Understanding the processes regulating the water quality functions of riparian zones are important to assess their effectiveness as buffer zones and to improve the management of the use of N fertilizers.
This PhD thesis investigates and quantify the heterogeneity in water fluxes to and from riparian zones and how the relative importance of groundwater-fed surface flow to subsurface flow affects nitrate delivery to streams. It was demonstrated how a wetland system crisscrossed with ditches and subsurface drains captures a high proportion of the regional groundwater discharging to the riparian zone. Sediment and water chemistry showed a high denitrification potential of the subsurface and re-infiltration of nitrate-rich surface water could be a very important factor in reducing the N-load to the stream. In summary, human alteration of extant flow patterns, affected residence times and the occurrence of denitrification “hot spots” in the riparian stream corridor, and hence the nitrate load to the stream.

The thesis is available for inspection at the PhD administration office at Rolighedsvej 23