Welcome to the blog of the Department of Environmental and Geographical Sciences at the University of Northampton. This will keep you up to date with both student and staff activities.

The Department of Environmental and Geographical Sciences includes staff with interests in biological sciences, conservation, ecology, environmental sciences, environmental statistics, geography and waste management. We offer a range of degree programmes and have a number of postgraduate research students. For more information about studying with us please visit http://www.northampton.ac.uk/.

Monday, 11 May 2015

Mitigating agricultural pollution - Mattie Biddulph (PhD Student)

Last week I embarked on my 25th and final fieldwork trip, 30 months after beginning my PhD. I have been saying that it will be my final outing for the last four, but it really was this time… probably.
My PhD is based around mitigation measures that can reduce agricultural pollution (sediment and contaminants). With 70% of the UK being agricultural land, this is a big issue to tackle. I have been working on two tributaries on the Hampshire Avon, on the borders of Dorset and Wiltshire. These upper reaches of the Hampshire Avon are part of a government-funded project, whereby three river catchments in England have been designated as ‘Demonstration Test Catchments’. Research is carried out in these catchments to find cheap, sustainable ways to reduce agricultural pollution of sediment and contaminants.

Such mitigation measures could be simply fencing along a riverbank or planting riparian vegetation. More specific, targeted measures can include: repairing degraded farm infrastructure, wetland creation, installation of settling systems, or changing farming practice. 

But are these measures actually working? Are they worth all the money and maintenance? I am collating the best methods that can test the effectiveness of these measures and monitor them over time. They need to be cheap, sustainable and replicable; in other words, they need to be easy to carry out and require minimal labour, so that these can be used on a larger scale for the long term. 

One method that I am using is to measure the amount of sediment stored on the riverbed, by carrying out “disturbance sampling”. To do this, a seal is created on the bed using a cylinder of known diameter and depth; any fine sediment in the top 5 cm of the bed is suspended by stirring it with a stick. The water is then collected and dried, and the weight of the remaining sediment will give you the amount of sediment stored on the bed per unit area. Looking at the changes to the riverbed over time, along with the properties of the sediment (geochemistry, particle size, organic matter etc.), will give an indication of the effectiveness of mitigation measures.

Disturbance sampling

One of my sites is on a dairy farm. When I started in December 2012, the main farm track was in extremely poor condition; huge amounts of sediment were being eroded, both from farm machinery, and the 270 strong herd of cattle that would trample along it to get to and from the fields each day. During and after rainfall, animal waste would also flow from the yard onto the track. This track then acted effectively as a terrestrial river, channelling runoff into the river, carrying with it huge amounts of sediment and contaminants. 

Farm track after a long period of rainfall, AKA, mud bath. 

Eight months into my research, the farm track was completely replaced, and a settling system was put in place to catch anything running off it. The settling system included a culvert, which was dug along the side of the track to collect runoff; this culvert was then connected to a pond, which in turn was connected to a ditch that eventually flows into the river. The aim of this was to allow as much sediment to settling on the bed of the pond and ditch as possible, before it reached the river. Almost two years of monitoring later, I will be able to analyse whether this mitigation option has had any positive effect on the quality of the river.

The farm track after resurfacing. The track has been cambered to 
direct  runoff into the vegetative culvert to the right of the track.
The ditch that runs between the settling pond and the river now
contains “v-notch weirs”, which are useful for trapping sediment
A clear difference in the colour of the water 
entering the river from the settling system.

To some of you this may seem very boring and of little consequence, which is fine, but to me it’s exciting, and I can’t wait to find out what’s been happening! This is just one of my sites, with a very specific mitigation measure, so feel free to ask me about the others if you want to know more (matilda.biddulph@northampton.ac.uk).