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Experimental Catchments (experimental + catchment)
Selected AbstractsPersistence of road runoff generation in a logged catchment in Peninsular MalaysiaEARTH SURFACE PROCESSES AND LANDFORMS, Issue 13 2007Alan D. Ziegler Abstract Measurements of saturated hydraulic conductivity (Ks) and diagnostic model simulations show that all types of logging road/trail in the 14·4 ha Bukit Tarek Experimental Catchment 3 (BTEC3) generate substantial Horton overland flow (HOF) during most storms, regardless of design and level of trafficking. Near-surface Ks(0,0·05 m) on the main logging road, skid trails and newly constructed logging terraces was less than 1, 2 and 34 mm h,1, respectively. Near-surface Ks on an abandoned skid trail in an adjacent basin was higher (62 mm h,1), owing to the development of a thin organic-rich layer on the running surface over the past 40 years. Saturated hydraulic conductivity measured at 0·25 m below the surface of all roads was not different (all <6 mm h,1) and corresponded to the Ks of the adjacent hillslope subsoil, as most roads were excavated into the regolith more than 0·5,1 m. After 40 years, only limited recovery in near-surface Ks occurred on the abandoned skid trail. This road generated HOF after the storage capacity of the upper near-surface layer was exceeded during events larger than about 20 mm. Thus, excavation into low- Ks substrate had a greater influence on the persistence of surface runoff production than did surface compaction by machinery during construction and subsequent use during logging operations. Overland flow on BTEC3 roads was also augmented by the interception of shallow subsurface flow traveling along the soil,saprolite/bedrock interface and return flow emerging from the cutbank through shallow biogenic pipes. The most feasible strategy for reducing long-term road-related impacts in BTEC3 is limiting the depth of excavation and designing a more efficient road network, including minimizing the length and connectivity of roads and skid trails. Copyright © 2007 John Wiley & Sons, Ltd. [source] Rapid simulated hydrologic response within the variably saturated near surfaceHYDROLOGICAL PROCESSES, Issue 3 2008Brian A. Ebel Abstract Column and field experiments have shown that the hydrologic response to increases in rainfall rates can be more rapid than expected from simple estimates. Physics-based hydrologic response simulation, with the Integrated Hydrology Model (InHM), is used here to investigate rapid hydrologic response, within the variably saturated near surface, to temporal variations in applied flux at the surface boundary. The factors controlling the speed of wetting front propagation are discussed within the Darcy,Buckingham conceptual framework, including kinematic wave approximations. The Coos Bay boundary-value problem is employed to examine simulated discharge, pressure head, and saturation responses to a large increase in applied surface flux. The results presented here suggest that physics-based simulations are capable of representing rapid hydrologic response within the variably saturated near surface. The new InHM simulations indicate that the temporal discretization and measurement precision needed to capture the rapid subsurface response to a spike increase in surface flux, necessary for both data-based analyses and evaluation of physics-based models, are smaller than the capabilities of the instrumentation deployed at the Coos Bay experimental catchment. Copyright © 2007 John Wiley & Sons, Ltd. [source] Physically based modelling of sediment generation and transport under a large rainfall simulatorHYDROLOGICAL PROCESSES, Issue 11 2006Russell Adams Abstract A series of large rainfall simulator experiments was conducted in 2002 and 2003 on a small plot located in an experimental catchment in the North Island of New Zealand. These experiments measured both runoff and sediment transport under carefully controlled conditions. A physically based hydrological modelling system (SHETRAN) was then applied to reproduce the observed hydrographs and sedigraphs. SHETRAN uses physically based equations to represent flow and sediment transport, and two erodibility coefficients to model detachment of soil particles by raindrop erosion and overland flow erosion. The rate of raindrop erosion also depended on the amount of bare ground under the simulator; this was estimated before each experiment. These erodibility coefficients were calibrated systematically for summer and winter experiments separately, and lower values were obtained for the summer experiments. Earlier studies using small rainfall simulators in the vicinity of the plot also found the soil to be less erodible in summer and autumn. Limited validation of model parameters was carried out using results from a series of autumn experiments. The modelled suspended sediment load was also sensitive to parameters controlling the generation of runoff from the rainfall simulator plot; therefore, we found that accurate runoff predictions were important for the sediment predictions, especially from the experiments where the pasture cover was good and overland flow erosion was the dominant mechanism. The rainfall simulator experiments showed that the mass of suspended sediment increased post-grazing, and according to the model this was due to raindrop detachment. The results indicated that grazing cattle or sheep on steeply sloping hill-country paddocks should be carefully managed, especially in winter, to limit the transport of suspended sediment into watercourses. Copyright © 2006 John Wiley & Sons, Ltd. [source] Changes in biogeochemical cycling following forest defoliation by pine wilt disease in Kiryu experimental catchment in Japan Naoko Tokuchi, Nobuhito Ohte, Satoru Hobara, Su-Jin Kim and Katsuyama Masanori.HYDROLOGICAL PROCESSES, Issue 17 20042004; Volume 18 Issue 1, Hydrological Processes, pages 272 The original article to which this Erratum refers was published in Hydrological Processes, 2004; Volume 18 Issue 14, pages 2727,2736. [source] Using Rock-Eval 6 pyrolysis for tracking fossil organic carbon in modern environments: implications for the roles of erosion and weatheringEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2006Yoann Copard Abstract This work relates to the debate on the fossil organic carbon (FOC) input in modern environments and its possible implication for the carbon cycle, and suggests the use of Rock-Eval 6 pyrolysis as a relevant tool for tracking FOC in such environments. Considering that such a delivery is mainly due to supergene processes affecting the continental surface, we studied organic matter in different reservoirs such as bedrocks, alterites, soils and rivers in two experimental catchments at Draix (Alpes de Haute Provence, France). Samples were subjected to geochemical (Rock-Eval 6 pyrolysis) investigations and artificial bacterial degradations. After comparing the geochemical fingerprint of samples, geochemical markers of FOC were defined and tracked in the different reservoirs. Our results confirm the contribution of FOC in modern soils and rivers and display the various influences of weathering and erosional processes on the fate of FOC during its exchange between these pools. In addition, the contrasting behaviour of these markers upon the supergene processes has also highlighted the refractory or labile characters of the fossil organic matter (FOM). Bedrock to river fluxes, controlled by gully erosion, are characterized by a qualitative and quantitative preservation of FOM. Bedrock to alterite fluxes, governed by chemical weathering, are characterized by FOC mineralization without qualitative changes in deeper alterites. Alterite to soils fluxes, controlled by (bio)chemical weathering, are characterized by strong FOC mineralization and qualitative changes of FOM. Thus weathering and erosional processes induce different FOM evolution and affect the fate of FOC towards the global carbon cycle. In this study, gully erosion would involve maintenance of an ancient sink for the global carbon cycle, while (bio)chemical processes provide a source of CO2. Finally, this study suggests that Rock-Eval 6 pyrolysis can be considered as a relevant tool for tracking FOC in modern environments. Copyright © 2006 John Wiley & Sons, Ltd. [source] An overview of the field and modelling studies on the effects of forest devastation on flooding and environmental issuesHYDROLOGICAL PROCESSES, Issue 5 2010Yuichi Onda Abstract Intensive field observations as well as monitoring of discharge, water quality, and soil erosion have been conducted in forest plantations in order to identify the effects of forest cover and management practices on runoff generation, sediment transport, and downstream environmental issues. Five experimental catchments, each with rather uniform lithology, were established in both managed and unmanaged plantations of Japanese cypress and cedar, as well as broadleaf forests. Field monitoring was conducted from sub-plots (e.g. splash cups) to small hillslope plots (0·5 × 2 m) to large hillslope-scale plots to first order streams (0·1,4 ha) and finally to larger catchments (>4 ha) in a nested structure. Remote sensing techniques were employed to identify broad scale forest stand and soil surface conditions. As part of this integrated study, these field-based monitoring and remote sensing techniques provide information for modelling runoff generation and developing adaptive management schemes with respect to catchment-scale water resources. Copyright © 2010 John Wiley & Sons, Ltd. [source] Runoff and peak flow responses to timber harvest and forest age in southern ChileHYDROLOGICAL PROCESSES, Issue 1 2006Professor Andrés Iroumé Abstract Runoff and peak flows in three experimental catchments with different forest conditions were analysed in a rainy temperate climate in southern Chile. The hydrological effects of clearcutting a Pinus radiata plantation covering 79·4% of the La Reina catchment were studied by analysing runoff and peak flows in the pre- and post-harvesting periods. Mean annual runoff increased 110% after timber harvesting. Clearcutting generated a 32% mean increase in peak flows. Peak flow and runoff were examined in two adjacent catchments with different forest conditions. The older plantation in Los Ulmos 1 increasingly consumed more water than the younger plantation established at Los Ulmos 2, whereas differences in peak flows between these two catchments were not significant. Runoff and peak flows comparisons not only reflected changes in forest cover, but also the effect of rainfall characteristics during the study periods and the basins' morphologies. Comparisons between pre- and post-harvesting peak discharges must be undertaken with caution, because a previous analysis at La Reina using a partial set of data overestimated changes in peak flows after timber harvesting. Copyright © 2005 John Wiley & Sons, Ltd. [source] A qualitative and quantitative evaluation of experimental model catchment evolutionHYDROLOGICAL PROCESSES, Issue 12 2003Dr G. R. Hancock Abstract Due to the geological time scales required for observation of catchment evolution, surrogates or analogues of field data are necessary to understand long-term processes. To investigate long-term catchment behaviour, two experimental model catchments that developed without rigid boundaries under controlled conditions are examined and a qualitative and quantitative analysis of their evolution is presented. Qualitatively, the experimental catchments have the visual appearance of field scale data. Observation demonstrates that changes in catchment shape and network form are conservative. Quantitative analysis suggests that the catchments reach an equilibrium form while a reduction in the channel network occurs. While the catchments are laboratory scale models, the results provide insights into field scale behaviour. Copyright © 2003 John Wiley & Sons, Ltd. [source] APPLICATION OF DIFFUSIVE TANK MODEL IN DRAINAGE ANALYSIS OF PADDY FIELDS,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 1 2004Rong-Song Chen ABSTRACT: A diffusive tank model has been successfully applied to the simulation of runoff from paddy fields in Japan because it can well describe the features of local water flows. The main goal of the study is to evaluate the performance of the diffusive tank model with the calibrated parameters obtained in Jyau-Shi to simulate discharge from paddy fields in two experimental catchments located in the areas of Shing-Ying and Ta-Liao, Southwestern Taiwan. The simulations were verified by comparing the model results with observed runoff data from the two experimental catchments. The model predicted the discharge from the paddy fields well. This indicates that the model with the calibrated parameters may be used in other paddy fields in Taiwan. [source] | ||||||||||