Development and Evaluation of an ODE Representation of 3D Subsurface Tile Drainage Flow Using the HLM Flood Forecasting System

We developed a new ordinary differential equation (ODE) to represent subsurface flows from hillslope with artificial drainage (tiling) into an adjacent channel. Our ODE is based on derived storage-discharge relationship high-resolutions HYDRUS3D simulations that solve 3D partial Richards' equations for (plot scale) internal surfaces, variable soil depth, hydraulic conductivity, and varying slope in the direction of flow. The does not capture hysteresis storage-drainage relation can only be captured using (PDEs), however simplification have major impacts modeled flows. nondimensional representation consistent with, provides explanation for, empirical used classical hydrological models such as ARNO (Arno River) Variable Infiltration Capacity (VIC) model simulate flows, which removes need parameter calibration. captures features by other simplifications DRAINMOD. coupled Hillslope Link Model (HLM) flood forecasting system allowing real-time regional simulation streamflow fluctuations floods over large domains. show (i) improves capability watershed scale hydrograph recessions better timing above thresholds multiple spatial scales 0.1 18,000 km2; (ii)using realistic values combined typical tile separation depth good predictive power at gauged basin outlets; (iii) parameters particular situations PDE framework.