A physically based distributed subsurface–surface flow dynamics model for forested mountainous catchments

Abstract

Abstract:This study was designed to develop a physically based hydrological model to describe the hydrological processes within forested mountainous river basins. The model describes the relationships between hydrological fluxes and catchment characteristics that are influenced by topography and land cover. Hydrological processes representative of temperate basins in steep terrain that are incorporated in the model include intercepted rainfall, evaporation, transpiration, infiltration into macropores, partitioning between preferential flow and soil matrix flow, percolation, capillary rise, surface flow (saturation-excess and return flow), subsurface flow (preferential subsurface flow and baseflow) and spatial water-table dynamics. The soil-vegetation-atmosphere transfer scheme used was the single-layer Penman-Monteith model, although a two-layer model was also provided. The catchment characteristics include topography (elevation, topographic indices), slope and contributing area, where a digital elevation model provided flow direction on the steepest gradient flow path. The hydrological fluxes and catchment characteristics are modelled based on the variable source-area concept, which defines the dynamics of the watershed response. Flow generated on land for each sub-basin is routed to the river channel by a kinematic wave model. In the river channel, the combined flows from sub-basins are routed by the Muskingum-Cunge model to the river outlet; these comprise inputs to the river downstream. The model was applied to the Hikimi river basin in Japan. Spatial decadal values of the normalized difference vegetation index and leaf area index were used for the yearly simulations. Results were satisfactory, as indicated by model efficiency criteria, and analysis showed that the rainfall input is not representative of the orographic lifting induced rainfall in the mountainous Hikimi river basin. Also, a simple representation of the effects of preferential flow within the soil matrix flow has a slight significance for soil moisture status, but is insignificant for river flow estimations.

A review of model applications for structured soils: a) Water flow and tracer transport

“…After model calibration, river flow in three subbasins was predicted between 1992 and 1996. Simulation results appeared satisfactory, except that peak flows were underestimated (Mulungu et al, 2005).…”

“…Overland flow is calculated using a linear reservoir (capacity) scheme. The 1D Distributed Subsurface-Surface Flow Dynamics Model, DSFDM (Mulungu et al, 2005) adds a PF component to the Famiglietti and Wood (1994) catchment scale model. Three soil layers are considered in DSFDM: in the top 1-m soil layer, macropore flow and lateral interflow may occur; the middle 'transmission' zone assumes vertical flow in the soil matrix, and the bottom layer with Darcy (lateral) flow of groundwater in the soil matrix.…”

“…However, the conclusions about PF remain uncertain, since the simple bucket model gave similar results. Modified DSFDM was applied to simulate river flow in the temperate forested Hikimi river basin (352 km 2 ) in a mountain region in Japan (Mulungu et al, 2005). Ten model parameters were calibrated against the river flow in 1991 using hourly rainfall data.…”

Quantification of the influence of preferential flow on slope stability using a numerical modelling approach

“…Preferential flow and solute transport have been simulated at various scales including the scales of pores, soil columns, hillslopes, and catchments (Šimůnek et al, 2003;Gerke, 2006;Köhne et al, 2009) using increasingly sophisticated models such as the dual-porosity/dual-permeability model (Gerke and van Genuchten, 1993a;Jarvis et al, 1991;Larsbo and Jarvis, 2003), the multi-permeability model (Wu et al, 2004;Greco, 2002;Gwo et al, 1995), and conceptual models (Armstrong et al, 2000;Weiler, 2005;Mulungu et al, 2005). The dual-permeability model is widely used because of its clear physical concept and powerful simulating ability (Roulier and Jarvis, 2003;Kodešová et al, 2005;Gerke and Köhne, 2004;Köhne et al, 2006;Christiansen et al, 2004;Weiler, 2005;Therrien and Sudicky, 2005;Vogel et al, 2000).…”

A model of hydrological and mechanical feedbacks of preferential fissure flow in a slow-moving landslide

“…In hillslope hydrological models preferential flow is commonly incorporated as enhanced vertical infiltration, rapid slope-parallel flow on the bedrock surface or modification of the saturated permeability function (Bogaard, 2002;Beckers and Alila, 2004;Kosugi et al, 2004;Mulungu et al, 2005;Zehe and Blöschl, 2004;Zhang et al, 2006) without accounting for spatial and temporal variation of the preferential flow paths characteristics. Weiler and McDonnell (2007) stressed that incorporation of the spatially dynamic nature of preferential flow systems for conceptualisation and parameterisation of the effect of lateral preferential flow on hillslope hydrology is one of the greatest challenge.…”