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DOI： 10.11408/jsidre1965.2004.679

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Language：English   Publisher：AMER WATER RESOURCES ASSOC  

A stochastic estimation of low flow in the upper reaches of streams is needed for the planning, development, and management of water resources and/or water use systems. In this paper, the definition and development procedure for the stochastic flow duration curve is presented and applied to five catchments located in eastern Japan and to two catchments in western Thailand. The probability distribution of N-year daily discharge data is extracted at various percentages of time for which specified discharges are equaled or exceeded in a water year. Such a distribution is usually represented with a straight line on log-normal probability paper. However, some of the probability plots for the annual minimum daily discharge are best represented with a straight line on Weibull probability paper. The effectiveness of the stochastic flow duration curve defined for the evaluation of flow regime is illustrated through its application. The ten year probability for the discharge exceeded 97 percent of the time may be recognized as an index of low flow. The recession shape of the lower part of the flow duration curve is dependent on the strength of low flow persistence.

DOI： 10.1111/j.1752-1688.2003.tb01560.x

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Language：English   Publisher：JOHN WILEY & SONS LTD  

The Distributed Hydrology Soil Vegetation Model is applied to the Redfish Creek catchment to investigate the suitability of this model for simulation of forested mountainous watersheds in interior British Columbia and other high-latitude and high-altitude areas. On-site meteorological data and GIS information on terrain parameters, forest cover, and soil cover are used to specify model input. A stepwise approach is taken in calibrating the model, in which snow accumulation and melt parameters for clear-cut and forested areas were optimized independent of runoff production parameters. The calibrated model performs well in reproducing year-to-year variability in the Outflow hydrograph, including peak flows. In the subsequent model performance evaluation for simulation of catchment processes, emphasis is put on elevation and temporal differences in snow accumulation and melt, spatial patterns of snowline retreat, water table depth, and internal runoff generation, using internal catchment data as much as possible. Although the overall model performance based on these criteria is found to be good, some issues regarding the Simulation of internal catchment processes remain. These issues are related to the distribution of meteorological variables over the catchment and a lack of information on spatial variability in soil properties and soil saturation patterns. Present data limitations for testing internal model accuracy serve to guide future data collection at Redfish Creek. This study also illustrates the L challenges that need to be overcome before distributed physically based hydrologic models can be used for simulating catchments with fewer data resources. Copyright (C) 2003 John Wiley Sons, Ltd.

DOI： 10.1002/hyp.1119

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Language：English   Publisher：INT ASSOC HYDROLOGICAL SCIENCES  

Comparison of flow regimes in the upper reaches of streams in the temperate zone (eastern Japan) and the tropical monsoon zone (western Thailand), and evaluation of an index of low flow are carried out aiming towards the synthesis of water resources evaluation. The flow regimes of the upper reaches of streams are stochastically evaluated by applying the stochastic flow duration (SFD) curve. On the basis of a comparison of values read from the SFD curve with the 10-year probability value, it is shown that the discharge exceeded 97% of time in the tropical monsoon zone is only about one-fifteenth that of the temperate zone. This difference indicates that this flow regime is uncomfortable for planning if a water resources planner evaluates a flow with the 10-year probability in the tropical zone. It may be argued that a more severe probability of occurrence (i.e. longer than 10 years) should be adopted for the design of water resources facilities in the tropical monsoon zone. By comparing the recession shape of the lower part of the flow duration curve, it is seen that the persistency of low flow in the temperate zone is stronger than that in the tropical monsoon zone. The index of low flow is also discussed by examining the relation between the index used in Japan and that in the United States of America. The relationship between the 10-year probability for annual minimum flow averaged over a consecutive period of seven days (Q(10.7)) of a given year and the 10-year probability value for the discharge exceeded 97% of the time (Q97(10)) is strong. This implies that the Q97(10) index used in Japan can be recognized as an index of low flow.

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Language：English   Publisher：AMER GEOPHYSICAL UNION  

[1] A hydrologic model of the mountainous snowmelt-dominated Redfish Creek catchment (British Columbia) is used to evaluate Interior Watershed Assessment Procedure (IWAP) guidelines regarding peak flow sensitivity to logging in different elevation bands of a basin. Simulation results suggest that peak flow increases are caused by greater snow accumulation and melt in clear-cut areas while similar evapotranspiration rates are predicted under forested and clear-cut conditions during spring high flow. Snow accumulation and melt are clearly related to elevation, but the relationship between logging elevation and peak flow change is more complex than perceived in the IWAP. Logging in the bottom 20% of the catchment causes little or no change in peak flow because of the small low-elevation snowpack and the timing of snowmelt, while clear-cut area alone appears to be a good indicator of peak flow increases due to logging at higher elevation. Temporal variability in peak flow changes due to clear-cutting is substantial and may depend more on temperatures during snowmelt than on the size of the snowpack. Long-term simulations are needed to improve quantitative estimates of peak flow change while the importance of watershed topographic characteristics for snowmelt and peak flow generation must be further examined.

DOI： 10.1029/2001WR000514

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DOI： 10.11408/jsidre1965.2001.281

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DOI： 10.1111/j.1752-1688.1997.tb03546.x

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