Mohid Land - Porous Media, a Tool for Modeling Soil Hydrology at Plot Scale and Watershed Scale

ABSTRACT

Hydrological modeling is becoming more important in water management. Soil hydrological models are increasingly being used to provide services to farmers and to water supply managers. This study tests the stability and adequability of MOHID LAND-PM in modelling soil water dynamics. Soil water flow and content was simulated in five soils with different soil textures (sand, sandy loam, clay, loam, and silt). The results were then compared with HYDRUS- 1D simulations using the same input data. Soil domain was divided into 100 layers up to a depth of 2 m. Five additional simulations were carried out in MOHID LAND-PM in order to quantify the error of reducing the number of layers to 10 (instead of 100) when discretizing the soil profile. This is relevant in a watershed model like MOHID LAND-PM since the computing time is greatly reduced. MOHID LAND-PM results were compared with those of HYDRUS using Nash- Sutcliffe model efficiency (NSE) and Percent bias (PBIAS). Soil volumetric water content, pressure heads, and soil water velocity were compared for 4 depths. For the water contents, NSE was above 0.87 for sand and above 0.97 for all other soils and layers except for the clay soil (NSE≥0.01). For pressure heads, NSE >0.46 for sand and >0.98 for all other soils and layers except clay (NSE≥-23.95). Statistical analysis shows a soil water velocity of NSE below 0.0 for most sand and clay depths, and above 0.58 NSE for all other soils. PBias shows that in general, MOHID LAND-PM tends to underestimate HYDRUS soil water content and velocities.

Keywords:

Infiltration, Hydrus, MOHID LAND-PM, Richards equation, soil water content, soil layer discretization.