Temporal dynamics between cattle in-stream presence and suspended solids in a headwater catchment

Julie A. Terry,* Clare McW.H. Benskin*, Emma F. Eastoe† and Philip M. Haygarth*

*Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ†Department of Mathematics and Statistics, Lancaster University, Lancaster LA1 4YFEmail: [email protected] 

Cattle in-stream activity is potentially an important contributor to water pollution from agriculture. Here we present research on the physical movements of cattle within a stream on suspended solid concentrations (SSC). This study used camera surveillance to monitor the in-stream activity of dairy cattle in an unfenced reach over a four-month period. Results were compared against high-resolution SSC data. Over the days that cattle grazed the field, 57.9% of the instances when SSC crossed the 25 mg l1 Freshwater Fish Directive guideline threshold can be attributed to cattle presence in the stream. Flow was the main driver of total sediments transported over the study period, and no relationship  was found between SSC and the absolute number of cattle feet in the water. Hysteresis analysis  indicated a ‘first-flush’ of local sediments rapidly mobilised during the non-cattle related SSC events, a result of cattle proximity to channel margins. Results demonstrate a temporal lag between cattle in-stream presence and a critical amount of their contribution to sediment load, and that monitoring only instantaneously with cattle activity may lead to underestimation of their pollution impact.
Environmental Science: Processes & Impacts DOI: 10.1039/c3em00686g