BUILDUP, WASHOFF, AND EVENT MEAN CONCENTRATIONS¹

Abstract

Most watershed water quality simulation models require the user to specify pollutant buildup and washoff rate parameters for pollutants, by land use. Buildup and washoff rates are difficult to measure directly, and only limited guidance and few observed data are available from the literature. Many studies, however, report storm event mean concentrations (EMCs). These EMCs must arise as a result of the buildup and washoff processes, but typically represent the net contribution from a variety of pervious and impervious surfaces. This paper explores the relationship between EMCs and buildup/washoff parameters. An assumption of the mathematical form of the buildup/washoff relationship gives an algebraic expression for the EMC consistent with model assumptions. This yields techniques to separate observed EMCs into contributions from different land uses and from pervious and impervious surfaces. Given this relationship, numerical optimization may be used to estimate site specific values of buildup and washoff parameters from observed storm EMCs for use in modeling. Use of this approach helps ensure that model parameters are consistent with observed data, providing a rational starting point for final model calibration. Several site examples demonstrate use of the method.

Advances in Landscape Runoff Water Quality Modelling: A Review

“…Since data requirements of the EMC model are less, it is easy to use. However, the EMC value can change between storms (Chiew and McMahon 1999;Butcher 2003), and hence the prediction of pollutant loads by the EMC model may be inaccurate for un-monitored storm events. To avoid this discrepancy arising in the EMC model, the sophisticated build-up wash-off (BUWO) models are formulated (Chen and Adams 2007).…”

“…Then the observed EMC is the runoff weighted sum of all EMCs from the individual land use (Butcher 2003). For these cases, the mathematical expression of EMC can be represented by Eq.…”

Simulation of Non-Structural BMP Performance Using Pollutant Buildup and Washoff Functions

“…Butcher (2003) used this approach to develop parameters for a watershed model employing buildup /washoff simulation for nutrients. Butcher (2003) used this approach to develop parameters for a watershed model employing buildup /washoff simulation for nutrients.…”

Relationship between sediment build-up characteristics and antecedent dry days on different urban road surfaces in Malaysia

“…These include studies in Australia (Ball et al 1998, Vaze and Chiew 2002, Vaze and Chiew 2004, Egodawatta and Goonetilleke 2006, Goonetilleke et al 2009, Mahbub et al 2010, Miguntanna et al 2010, Scotland (Deletic and Orr 2005), China (Bian and Zhu 2008) and the USA (Butcher 2003, Kim et al 2006. However, specific data on pollutant build-up for urban catchment in Malaysia and other tropical cities are still scarce.…”