Rainfall-runoff is a highly nonlinear and spatially auto-correlated process. The understanding of rainfall-runoff process is important for the assessment, protection and management of water resources. Modelling approach used for management of water quality are piggy-backed to rainfall-runoff process. Improvement in and detailed understanding of the runoff generation processes is helpful in the development of better management approaches to assess the pollutants losses from agricultural land use activities. There is also a need for detailed investigation in the spatial and temporal variations of runoff generation parameters, and the means for their aggregation in modelling to address the scale issues that arise when hydrological algorithms developed from laboratory/plot scale theory are applied on the field/watershed scale. The present study was undertaken with the objectives of investigating the dominant runoff generation mechanism and runoff generation areas on a field scale, identifying the dominant hydrologic parameters affecting the runoff generation mechanism and developing a technique for upscaling of dominant hydrologic parameters from plot to field scale.; Results show that the bulk density, total porosity, soil texture, saturated hydraulic conductivity, and suction at the wetting front were more spatially variables along the slope than across the slope of the field. The spatial variability of soil physical and hydraulic properties on a field scale can be represented by a fractal relationship. The topographic data also shows a fractal behaviour on plot and field scale.; Firstly, the runoff starts from the areas with low topography, low hydraulic conductivity, high bulk density, and high initial soil-water content. The runoff generates due to Horton mechanism. The runoff generation area increases as the duration of storm event increases. The statistical analysis shows that saturated hydraulic conductivity, bulk density, elevation and field slope were dominant parameters for summer period, whereas saturated hydraulic conductivity, bulk density, elevation, field slope and initial soil-water content were dominant parameters for fall period. A procedure to scale-up the dominant hydrologic parameters from plot to field scale was developed. The overall conclusion of the study is that field saturated hydraulic conductivity is most significant spatially variable parameter.
展开▼
