Assessment of Macropore Component of RZWQM2 in Simulating Hourly Subsurface Drainage and Peaks

Abstract

Highlights The macropore component of RZWQM2 was evaluated using hourly drainage and rainfall data. Activating macropore components improved hourly drainage peak simulation. Macropore flow simulated by RZWQM2 was insensitive to the macroporosity and pore radius. Abstract. Understanding preferential flow through soil macropores is critical to effectively managing subsurface drainage water quantity and quality. This study aims to assess the macropore component of the Root Zone Water Quality Model (RZWQM2) in simulating subsurface tile flow with a high time resolution. Observed hourly tile flow rates from two experimental sites in Ontario, Canada (2008-2011) and Iowa, USA (2007-2008) were used to evaluate the importance of including a macropore flow component in subsurface drainage simulation. Activating the macropore component in the model improved the simulation of hourly drainage peaks, especially peak amplitude. Still, it did not improve the simulation of the total drainage amount for each rainfall event. Simulation of the drainage peak recession varied from peak to peak, suggesting that further studies are warranted for drainage flow in the model. In general, the macropore component in the RZWQM2 model improved subsurface peak subsurface simulation at the hourly resolution. However, further investigation and model modifications are needed to improve the drainage simulation’s timing and quality for RZWQM2’s hydrologic simulation of macropore flow and subsurface drainage. Keywords: Macropores, RZWQM2, Subsurface drainage modelling, Preferential flow simulation.