Prediction of storm transfers and annual loads with data-based mechanistic models using high-frequency data

Ockenden, Mary and Tych, Wlodzimierz and Beven, Keith John and Collins, Adrian and Evans, Robert and Falloon, Peter and Forber, Kirsty Jessica and Hiscock, Kevin and Hollaway, Michael John and Kahana, Ron and Macleod, Christopher J.A. and Villamizar, Martha and Wearing, Catherine Louise and Withers, Paul J.A and Zhou, Jian and Benskin, Clare McWilliam Haldane and Burke, Sean and Cooper, Richard and Freer, Jim and Haygarth, Philip Matthew (2017) Prediction of storm transfers and annual loads with data-based mechanistic models using high-frequency data. Hydrology and Earth System Sciences, 21. pp. 6425-6444. ISSN 1027-5606

Abstract

Excess nutrients in surface waters, such as phosphorus (P) from agriculture, result in poor water quality, with adverse effects on ecological health and costs for remediation. However, understanding and prediction of P transfers in catchments have been limited by inadequate data and over-parameterised models with high uncertainty. We show that, with high temporal resolution data, we are able to identify simple dynamic models that capture the P load dynamics in three contrasting agricultural catchments in the UK. 10 For a flashy catchment, a linear, second-order (two pathways) model for discharge gave high simulation efficiencies for short-term storm sequences and was useful in highlighting uncertainties in out-of-bank flows. A model with nonlinear rainfall input was appropriate for predicting seasonal 15 or annual cumulative P loads where antecedent conditions affected the catchment response. For second-order models, the time constant for the fast pathway varied between 2 and 15 h for all three catchments and for both discharge and P, confirming that high temporal resolution data are necessary 20 to capture the dynamic responses in small catchments (10–50 km2/. The models led to a better understanding of the dominant nutrient transfer modes, which will be helpful in determining phosphorus transfers following changes in precipitation patterns in the future.