Estimating the contribution of in-stream cattle faeces deposits to nutrient loading in an English Chalk stream

Numerous studies have shown that the addition of faecal matter from livestock to aquatic ecosystems can have a detrimental effect upon water quality. English Chalk streams, as groundwater-dominated rivers of high ecological importance, are particularly susceptible to nutrient loading from cattle faeces. Naturally low concentrations of nitrogen, phosphorus and potassium in such rivers increase their vulnerability to external perturbation from organic matter inputs. Despite this, the amount of faeces directly contributed by livestock such as cattle to a river system is rarely quantified. To provide an assessment of nutrient loading due to cattle, a study combining observational data of animal behaviour with faecal analysis was undertaken in an English Chalk stream. Results show that cattle faeces was 89.4% water, containing 0.79% nitrogen, 0.43% phosphorous and 0.43% potassium by wet mass. It was estimated that a herd of 33 cattle deposited over 8 tonnes of faeces into a 770 m river reach over a seven-month period in 2010. This loading is estimated to have increased in-stream nitrogen, phosphorus and potassium concentrations in the reach by 0.0036 mg l−1, 0.002 mg l−1 and 0.002 mg l−1 respectively; a small proportion of the overall nutrient content of the river. Moreover, it has been demonstrated that by combining behavioural data with faecal data it is possible to estimate the likely nutrient loading due solely to direct inputs from cattle faeces. With sufficient data, calculations such as those employed in this study can be used to provide accurate estimates of the nutrient loading due to livestock in watercourses.