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Runoff Generation Processes (runoff + generation_process)
Selected AbstractsGIS-Based Predictive Models of Hillslope Runoff Generation Processes,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2009Mansour D. Leh Abstract:, Successful nonpoint source pollution control using best management practice placement is a complex process that requires in-depth knowledge of the locations of runoff source areas in a watershed. Currently, very few simulation tools are capable of identifying critical runoff source areas on hillslopes and those available are not directly applicable under all runoff conditions. In this paper, a comparison of two geographic information system (GIS)-based approaches: a topographic index model and a likelihood indicator model is presented, in predicting likely locations of saturation excess and infiltration excess runoff source areas in a hillslope of the Savoy Experimental Watershed located in northwest Arkansas. Based on intensive data collected from a two-year field study, the spatial distributions of hydrologic variables were processed using GIS software to develop the models. The likelihood indicator model was used to produce probability surfaces that indicated the likelihood of location of both saturation and infiltration excess runoff mechanisms on the hillslope. Overall accuracies of the likelihood indicator model predictions varied between 81 and 87% for the infiltration excess and saturation excess runoff locations respectively. On the basis of accuracy of prediction, the likelihood indicator models were found to be superior (accuracy 81-87%) to the predications made by the topographic index model (accuracy 69.5%). By combining statistics with GIS, runoff source areas on a hillslope can be identified by incorporating easily determined hydrologic measurements (such as bulk density, porosity, slope, depth to bed rock, depth to water table) and could serve as a watershed management tool for identifying critical runoff source areas in locations where the topographic index or other similar methods do not provide reliable results. [source] The impact of groundwater,surface water interactions on the water balance of a mesoscale lowland river catchment in northeastern GermanyHYDROLOGICAL PROCESSES, Issue 2 2007Stefan Krause Abstract The glacially formed northeastern German lowlands are characterized by extensive floodplains, often interrupted by relatively steep moraine hills. The hydrological cycle of this area is governed by the tight interaction of surface water dynamics and the corresponding directly connected shallow groundwater aquifer. Runoff generation processes, as well as the extent and spatial distribution of the interaction between surface water and groundwater, are controlled by floodplain topography and by surface water dynamics. A modelling approach based on extensive experimental analyses is presented that describes the specific water balance of lowland areas, including the interactions of groundwater and surface water, as well as reflecting the important role of time-variable shallow groundwater stages for runoff generation in floodplains. In the first part, experimental investigations of floodplain hydrological characteristics lead to a qualitative understanding of the water balance processes and to the development of a conceptual model of the water balance and groundwater dynamics of the study area. Thereby model requirements which allow for an adequate simulation of the floodplain hydrology, considering also interactions between groundwater and surface water have been characterized. Based on these analyses, the Integrated Modelling of Water Balance and Nutrient Dynamics (IWAN) approach has been developed. This consists of coupling the surface runoff generation and soil water routines of the deterministic, spatially distributed hydrological model WASIM-ETH-I with the three-dimensional finite-difference-based numerical groundwater model MODFLOW and Processing MODFLOW. The model was applied successfully to a mesoscale subcatchment of the Havel River in northeast Germany. It was calibrated for two small catchments (1·4 and 25 km2), where the importance of the interaction processes between groundwater and surface waters and the sensitivity of several controlling parameters could be quantified. Validation results are satisfying for different years for the entire 198 km2 catchment. The model approach was further successfully tested for specific events. The experimental area is a typical example of a floodplain-dominated landscape. It was demonstrated that the lateral flow processes and the interactions between groundwater and surface water have a major importance for the water balance and periodically superimposed on the vertical runoff generation. Copyright © 2006 John Wiley & Sons, Ltd. [source] A Paradigm Shift in Hydrology: Storage Thresholds Across Scales Influence Catchment Runoff GenerationGEOGRAPHY COMPASS (ELECTRONIC), Issue 7 2010Christopher Spence A paradigm shift is occurring in the science surrounding runoff generation processes. Results of recent field investigations in landscapes and during periods previously unobservable are shaping new ideas on how runoff is generated and transferred from the hillslope to the catchment outlet. The previous paradigm saw runoff generation and contributing area variability as a continuum. The new paradigm is based not on continual storage satisfaction and runoff generation but threshold-mediated, connectivity-controlled processes dictated by heterogeneity in the catchment. This review focuses on the body of literature summarizing research on storage, storage thresholds and runoff generation, particularly over the last several years during which this paradigm shift has occurred. Storage thresholds that control the release of water exist at scales as small as the soil matrix and as large as the catchment. Hysteresis in storage,runoff relationships at all scales manifest because of these thresholds. Because storage thresholds at a range of scales have now been recognized as important, connectivity has become an important concept crucial to understanding how water is transferred through a catchment. This new paradigm requires basins to be instrumented within the context of a water budget investigation, with measurements taken within key catchment units, in order to be successful. New model approaches that incorporate connectivity are required to address the findings of field hydrologists. These steps are crucial if our community wishes to adopt the holisitic view of the catchment necessary to answer the questions posed to us by the society. [source] Process-oriented catchment modelling and multiple-response validationHYDROLOGICAL PROCESSES, Issue 2 2002S. Uhlenbrook Abstract The conceptual rainfall runoff model TAC (tracer-aided catchment model) has been developed based on the experimental results of tracer hydrological investigations at the mountainous Brugga and Zastler basins (40 and 18·4 km2). The model contains a physically realistic description of the runoff generation, which includes seven unit types each with characteristic dominating runoff generation processes. These processes are conceptualized by different linear and non-linear reservoir concepts. The model is applied to a period of 3·2 years on a daily time step with good success. In addition, an extensive model validation procedure was executed. Therefore, additional information (i.e. runoff in subbasins and a neighbouring basin, tracer concentrations and calculated runoff components) was used besides the simulated discharge of the basin investigated. This study shows the potential of tracer data for hydrological modelling. On the one hand, they are good tools to investigate the runoff generation processes. This is the basis for developing more realistic conceptualizations of the runoff generation routine. On the other hand, tracer data can serve as multi-response data to assess and validate a model. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||