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Runoff Mechanisms (runoff + mechanism)

Distribution by Scientific Domains

Engineering	100%

Selected Abstracts

Delineating runoff processes and critical runoff source areas in a pasture hillslope of the Ozark Highlands

HYDROLOGICAL PROCESSES, Issue 21 2008
M. D. Leh
Abstract The identification of runoff contributing areas would provide the ideal focal points for water quality monitoring and Best Management Practice (BMP) implementation. The objective of this study was to use a field-scale approach to delineate critical runoff source areas and to determine the runoff mechanisms in a pasture hillslope of the Ozark Highlands in the USA. Three adjacent hillslope plots located at the Savoy Experimental Watershed, north-west Arkansas, were bermed to isolate runoff. Each plot was equipped with paired subsurface saturation and surface runoff sensors, shallow groundwater wells, H-flumes and rain gauges to quantify runoff mechanisms and rainfall characteristics at continuous 5-minute intervals. The spatial extent of runoff source areas was determined by incorporating sensor data into a geographic information-based system and performing geostatistical computations (inverse distance weighting method). Results indicate that both infiltration excess runoff and saturation excess runoff mechanisms occur to varying extents (0,58% for infiltration excess and 0,26% for saturation excess) across the plots. Rainfall events that occurred 1,5 January 2005 are used to illustrate the spatial and temporal dynamics of the critical runoff source areas. The methodology presented can serve as a framework upon which critical runoff source areas can be identified and managed for water quality protection in other watersheds. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Rainfall-discharge relationships for a monsoonal climate in the Ethiopian highlands

HYDROLOGICAL PROCESSES, Issue 7 2008
Ben M. Liu
Abstract This study presents a simple rainfall-discharge analysis for the Andit Tid, Anjeni, and Maybar watersheds of northern Ethiopia. The Soil Conservation Research Programme (SCRP) established monitoring stations in each of these sites during the 1980s, with climate and stream flow measurements being recorded up to the present. To show how these data could be used to provide insight into catchment-level runoff mechanisms, simple linear relationships between effective precipitation and runoff are developed for each watershed, with the conclusion that all three watersheds exhibit consistent hydrologic behaviour after approximately 500 mm of cumulative effective seasonal rainfall has fallen since the beginning of season. After the 500 mm rainfall threshold is reached, approximately 50% of any further precipitation on these watersheds will directly contribute to catchment runoff. Copyright © 2008 John Wiley & Sons, Ltd. [source]

On the effects of triangulated terrain resolution on distributed hydrologic model response

HYDROLOGICAL PROCESSES, Issue 11 2005
Enrique R. Vivoni
Abstract Distributed hydrologic models based on triangulated irregular networks (TIN) provide a means for computational efficiency in small to large-scale watershed modelling through an adaptive, multiple resolution representation of complex basin topography. Despite previous research with TIN-based hydrology models, the effect of triangulated terrain resolution on basin hydrologic response has received surprisingly little attention. Evaluating the impact of adaptive gridding on hydrologic response is important for determining the level of detail required in a terrain model. In this study, we address the spatial sensitivity of the TIN-based Real-time Integrated Basin Simulator (tRIBS) in order to assess the variability in the basin-averaged and distributed hydrologic response (water balance, runoff mechanisms, surface saturation, groundwater dynamics) with respect to changes in topographic resolution. Prior to hydrologic simulations, we describe the generation of TIN models that effectively capture topographic and hydrographic variability from grid digital elevation models. In addition, we discuss the sampling methods and performance metrics utilized in the spatial aggregation of triangulated terrain models. For a 64 km2 catchment in northeastern Oklahoma, we conduct a multiple resolution validation experiment by utilizing the tRIBS model over a wide range of spatial aggregation levels. Hydrologic performance is assessed as a function of the terrain resolution, with the variability in basin response attributed to variations in the coupled surface,subsurface dynamics. In particular, resolving the near-stream, variable source area is found to be a key determinant of model behaviour as it controls the dynamic saturation pattern and its effect on rainfall partitioning. A relationship between the hydrologic sensitivity to resolution and the spatial aggregation of terrain attributes is presented as an effective means for selecting the model resolution. Finally, the study highlights the important effects of terrain resolution on distributed hydrologic model response and provides insight into the multiple resolution calibration and validation of TIN-based hydrology models. Copyright © 2005 John Wiley & Sons, Ltd. [source]

GIS-Based Predictive Models of Hillslope Runoff Generation Processes,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2009
Mansour 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]