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1.
A comparison is carried out between historical records of the flow measured in Kinneret watershed during and prior to the time of cloud seeding for rainfall enhancement. Precipitation series for the control area of the meteorological experimentation serve as a reference for the comparison. The fluctuations of the flow, which would have occurred unless the effect of the seeding, are estimated by a linear regression on the precipitation as the control. The regression parameters are calibrated separately for the unseeded and for the seeded time series. The model with the parameters calibrated for the unseeded series is applied on the rainfall recorded during the seeded time, and vice versa. The difference between the measured and the computed data is attributed to the effect of cloud seeding. Similar comparisons are carried out with respect to rainfall series recorded at the target area and at the edge of the enhanced area.The results indicate that the flow from the affected sector of the watershed has been enhanced, with respect to the control, by 31×106 m 3/year, at a significance level of 31. This enhancement is 5% of the volume which is generated in that area. The rates found with respect to the rainfall at the edge are higher than those found with respect to the control, while those with respect to the rainfall at the center of the target area are lower.  相似文献   

2.
Postfire runoff and erosion are a concern, and more data are needed on the effects of wildfire at the watershed‐scale, especially in the Colorado Front Range. The goal of this study was to characterize and compare the streamflow and suspended sediment yield response of two watersheds (Bobcat Gulch and Jug Gulch) after the 2000 Bobcat fire. Bobcat Gulch had several erosion control treatments applied after the fire, including aerial seeding, contour log felling, mulching, and straw wattles. Jug Gulch was partially seeded. Study objectives were to: (1) measure precipitation, streamflow, and sediment yields; (2) assess the effect of rainfall intensity on peak discharges, storm runoff, and sediment yields; (3) evaluate short‐term hydrologic recovery. Two months after the fire, a storm with a maximum 30 min rainfall intensity I30 of 42 mm h?1 generated a peak discharge of 3900 l s?1 km?2 in Bobcat Gulch. The same storm produced less than 5 l s?1 km?2 in Jug Gulch, due to less rainfall and the low watershed response. In the second summer, storms with, I30 of 23 mm h?1 and 32 mm h?1 generated peak discharges of 1100 l s?1 km?2 and 1700 l s?1 km?2 in the treated and untreated watersheds respectively. Maximum water yield efficiencies were 10% and 17% respectively, but 18 of the 23 storms returned ≤2% of the rainfall as runoff, effectively obscuring interpretation of the erosion control treatments. I30 explained 86% of the variability in peak discharges, 74% of the variability in storm runoff, and >80% of the variability in sediment yields. Maximum single‐storm sediment yields in the second summer were 370 kg ha?1 in the treated watershed and 950 kg ha?1 in the untreated watershed. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

3.
Predicting the timing of overland flow in burned watersheds can help to estimate debris-flow timing and the location of debris-flow initiation. Numerical models can produce flow predictions, but they are limited by our knowledge of appropriate model parameters. Moreover, opportunities to test and calibrate model parameters in post-wildfire settings are limited by available data (measurements of debris-flow timing are rare). In this study, we use a unique data set of rainfall and flow-timing data to test the extent to which model parameters can be generalized from an individual watershed to other watersheds (0.01 km 2 to >1km 2) within a burned area. Simulations suggest that a single, low, saturated hydraulic conductivity value can be used in post-wildfire landscapes with reasonable results. By contrast, we found that watershed-scale effective Manning roughness parameter values decrease as a power-law function of basin drainage area. Thus a Manning roughness parameter calibrated for a single basin within a burned area may not provide adequate results in a different watershed. However, when flow velocity is modeled independently for hillslopes and channels, and different roughness parameters are used for those morphometric units, there is no drainage-area dependence on the roughness parameters. Moreover, we found that it was possible to use field-measured grain size data to parameterize the roughness for both hillslopes and channels. Thus our results show that, employing this generalizable approach, it is possible to use field measurements to fully parameterize a model that produces peak flow timing to within a few minutes in storms lasting several hours. Further, we demonstrate how model simulations can be leveraged to identify areas within a watershed that are most susceptible to debris flows. This modeling approach could be used for decision making in hazardous burned areas and would be especially useful in ungaged basins. © 2019 John Wiley & Sons, Ltd.  相似文献   

4.
Distributed watershed models are beneficial tools for the assessment of management practices on runoff and water‐induced erosion. This paper evaluates, by application to an experimental watershed, two promising distributed watershed‐scale sediment models in detail: the Kinematic Runoff and Erosion (KINEROS‐2) model and the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. The physics behind each model are to some extent similar, though they have different watershed conceptualizations. KINEROS‐2 was calibrated using three rainfall events and validated over four separate rainfall events. Parameters estimated by this calibration process were adapted to GSSHA. With these parameters, GSSHA generated larger and retarded flow hydrographs. A 30% reduction in both plane and channel roughness in GSSHA along with the assumption of Green‐Ampt conductivity KG‐A = Ks, where Ks is the saturated conductivity, resulted in almost identical hydrographs. Sediment parameters not common in both models were calibrated independently of KINEROS‐2. A comparative discussion of simulation results is presented. Even though GSSHA's flow component slightly overperformed KINEROS‐2, the latter outperformed GSSHA in simulations for sediment transport. In spite of the fact that KINEROS‐2 is not geared toward continuous‐time simulations, simulations performed with both models over a 1 month period generated comparable results. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

5.
Groundwater flow modelling of the Kwa Ibo River watershed in Abia State of Nigeria is presented in this paper with the aim of assessing the degree of interaction between the Kwa Ibo River and the groundwater regime of the thick sandy aquifer. The local geology of the area comprises the Quaternary to recent Benin Formation. Potential aquifer zones that were delineated earlier using geoelectrical resistivity soundings and borehole data for the area formed the basis for groundwater flow modelling. The watershed has been modelled with a grid of 65 rows by 43 columns and with two layers. Lateral inflow from the north has been simulated with constant heads at the Government College, Umuahia, and outflow at Usaka Elegu in the south. The Kwa Ibo River traverses the middle of the watershed from north to south. The river‐stage data at Umudike, Amawom, Ntalakwu and Usaka Elegu have been used for assigning surface water levels and riverbed elevations in the model. Permeability distribution was found to vary from 3 to 14·5 m day?1. Natural recharge due to rainfall formed the main input to the aquifer system, and abstraction from wells was the main output. A steady‐state groundwater flow simulation was carried out and calibrated against the May 1980 water levels using 26 observation wells. The model computations have converged after 123 iterations. Under the transient‐state calibration, the highest rainfall (and hence groundwater recharge) over the 10‐year study period was recorded in 1996, whereas the lowest was recorded in 1991. The computed groundwater balance of 55 274 m3 day?1 was comparable to that estimated from field investigations. Results from the modelling show that abstraction is much less than groundwater recharge. Hence there is the possibility for additional groundwater exploitation in the watershed through drilling of boreholes. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

6.
The objective of this study was to analyse changes in stream flow patterns with reference to dynamics in land cover/use in a typical watershed, the Chemoga, in northwestern highland Ethiopia. The results show that, between 1960 and 1999, total annual stream flow decreased at a rate of 1 · 7 mm year−1, whereas the annual rainfall decreased only at a rate of 0 · 29 mm year−1. The decrease in the stream flow was more pronounced during the dry season (October to May), for which a statistically significant decline (0 · 6 mm year−1) was observed while the corresponding rainfall showed no discernible trend. The wet season (June to September) rainfall and stream flow did not show any trends. Extreme low flows analysed at monthly and daily time steps reconfirmed that low flows declined with time, the changes being highly significant statistically. Between 1960 and 1999, the monthly rainfall and stream flow amounts of February (month of lowest long‐term mean flow) declined by 55% and 94% respectively. Similarly, minimum daily flows recorded during the three driest months (December to February) showed statistically highly significant declines over the same period. It declined from 0 · 6 m3 s−1 to 0 · 2 m3 s−1 in December, from 0 · 4 m3 s−1 to 0 · 1 m3 s−1 in January and from 0 · 4 m3 s−1 to 0 · 02 m3 s−1 in February (1 · 0 m3 s−1 = 0 · 24 mm day−1 in the Chemoga watershed). In contrast, extreme high flows analysed at monthly (for August) and daily (July to September) time steps did not reveal discernible trends. The observed adverse changes in the stream flow have partly resulted from changes in land cover/use and/or degradation of the watershed that involved destruction of natural vegetative covers, expansion of croplands, overgrazing and increased area under eucalypt plantations. The other contributory factor has been the increased dry‐season water abstraction to be expected from the increased human and livestock populations in the area. Given the significance of the stream flow as the only source of water to the local people, a set of measures aimed at reducing magnitudes of surface runoff generation and increasing groundwater recharge are required to sustain the water resource and maintain a balanced dry‐season flow in the watershed. Generally, an integrated watershed management approach, whereby the whole of the watershed can be holistically viewed and managed, would be desirable. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

7.
Afforestation has been suggested as a means of improving soil and water conservation in north‐western China, especially on the Loess Plateau. Understanding of the hydrological responses to afforestation will help us develop sustainable watershed management strategies. A study was conducted during the period of 1956 to 1980 to evaluate runoff responses to afforestation in a watershed on the Loess Plateau with an area of 1·15 km2, using a paired watershed approach. Deciduous trees, including locust (locusta L.), apricot (praecox L.) and elm (ulmus L.), were planted on about 80% of a treated watershed, while a natural grassland watershed remained unchanged. It was estimated that cumulative runoff yield in the treated watershed was reduced by 32% as a result of afforestation. A significant trend was also observed that shows annual runoff reduction increases with the age of the trees planted. Reduction in monthly runoff occurred mainly from June to September, which was ascribed to greater rainfall and utilization by trees during this period. Afforestation also resulted in reduction in the volume and peak flow of storm runoff events in the treated watershed with greater reduction in peak flow. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

8.
Situated at the foot of the Pichincha volcano, the city of Quito is frequently subjected to hydroclimatic hazards. In 1995 an 11·2 km2 watershed, located in the vicinity of the city, was equipped with eight rain gauges and two flow gauges to better understand the local rainfall/runoff transformation processes. Rainfall simulation experiments were carried out on more than 40 one‐square‐metre plots to measure infiltration point‐processes. The high density of measurement devices allowed us to identify the origin and nature of the various contributions to runoff for the different physiographic units of the watershed: urban area from an altitude of 2800 to 3200 m; farmland, pasture and forested land, and finally páramo above 3900 m. Runoff occurs mainly in the lower part of the basin and is caused by urbanization; however, the natural soils of this area can also produce Hortonian runoff, which is predominant in a few events. This contribution can be studied through rainfall simulation experiments. In the upper natural zone, the younger and more permeable soils generate less runoff on the slopes. However, almost permanently saturated contributing areas, which are located in the bottom of the quebradas, may generate flood events, the size of which depends on the extent of the area concerned. Variations in the runoff coefficients are related first to the baseflow and second to the amount of rainfall in the previous 24 h. This analysis, which underlines the complexity of a small, peri‐urban, volcanic catchment, is a necessary preliminary to runoff modelling in an area where very few experiments have been carried out on small catchments. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

9.
A cell‐based long‐term hydrological model (CELTHYM) that can be integrated with a geographical information system (GIS) was developed to predict continuous stream flow from small agricultural watersheds. The CELTHYM uses a cell‐by‐cell soil moisture balance approach. For surface runoff estimation, the curve number technique considering soil moisture on a daily basis was used, and release rate was used to estimate baseflow. Evapotranspiration was computed using the FAO modified Penman equation that considered land‐use‐based crop coefficients, soil moisture and the influence of topography on radiation. A rice paddy field water budget model was also adapted for the specific application of the model to East Asia. Model sensitivity analysis was conducted to obtain operational information about the model calibration parameters. The CELTHYM was calibrated and verified with measured runoff data from the WS#1 and WS#3 watersheds of the Seoul National University, Department of Agricultural Engineering, in Hwaseong County, Kyounggi Province, South Korea. The WS#1 watershed is comprised of about 35·4% rice paddy fields and 42·3% forest, whereas the WS#3 watershed is about 85·0% forest and 11·5% rice paddy fields. The CELTHYM was calibrated for the parameter release rate, K, and soil moisture storage coefficient, STC, and results were compared with the measured runoff data for 1986. The validation results for WS#1 considering all daily stream flow were poor with R2, E2 and RMSE having values of 0·40, ?6·63 and 9·69 (mm), respectively, but validation results for days without rainfall were statistically significant (R2 = 0·66). Results for WS#3 showed good agreement with observed data for all days, and R2, E2 and RMSE were 0·92, 0·91 and 2·23 (mm), respectively, suggesting potential for CELTHYM application to other watersheds. The direct runoff and water balance components for watershed WS#1 with significant areas of paddy fields did not perform well, suggesting that additional study of these components is needed. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

10.
Spatially distributed hydrometeorological and plant information within the mountainous tropical Panama Canal watershed is used to estimate parameters of the Penman–Monteith evapotranspiration formulation. Hydrometeorological data from a few surface climate stations located at low elevations in the watershed are complemented by (a) typical wet‐ and dry‐season fields of temperature, wind, water vapour and pressure produced by a mesoscale atmospheric model with a 3 × 3 km2 spatial and hourly temporal resolution, and (b) leaf area index fields estimated over the watershed during a few years using satellite data with two different spatial and temporal resolutions. The mesoscale model estimates of spatially distributed surface hydrometeorological variables provide the basis for the extrapolation of the surface climate station data to produce input for the Penman–Monteith equation. The satellite information and existing digital spatial databases of land use and land cover form the basis for the estimation of Penman–Monteith spatially distributed parameter values. Spatially distributed 3 × 3 km2 potential evapotranspiration estimates are obtained for the 3300 km2 Panama Canal watershed. Estimates for Gatun Lake within the watershed are found to reproduce well the monthly and annual lake evaporation obtained from submerged pans. Sensitivity analysis results of potential evapotranspiration estimates with respect to cloud cover, dew formation, leaf area index distribution and mesoscale model estimates of surface climate are presented and discussed. The main conclusion is that even the limited spatially distributed hydrometeorological and plant information used in this study contributes significantly toward explaining the substantial spatial variability of potential evapotranspiration in the watershed. These results also allow the determination of key locations within the watershed where additional surface stations may be profitably placed. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

11.
The model presented in the complementary document entitled, Reservoir rainfall‐runoff geomorphological model I: parameter application and analysis is analysed, calibrated and validated in this paper. The accuracy of simulated hydrographs is analysed by means of the efficiency defined by Nash and Sutcliffe. The sensitivity of the influence of five parameters on the behaviour of the model developed is analysed. Two different calibration and validation processes of Reservoir rainfall‐runoff geomorphological model are performed in Aixola watershed. Twelve events have been selected for calibrations and 25 for validations. With the first calibration and validation process, the model parameters are set by assigning the medians' values of the distributions obtained by means of the optimum results. The second process is performed by calibrating the most determinant parameter in the adjustment, which is the one that indicates the proportion of infiltrated water that is retained and does not flow; this is done with an empirical formulation depending on the event characteristics. Subsequently, the obtained results are validated. This last process has achieved very good adjustments in both calibrated and validated events. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

12.
Evapotranspiration (ET) and canopy wetness were measured over a 2‐year intensive field campaign at the Chi‐Lan Mountain cloud forest site in Taiwan. Eddy covariance and sap flow methods were applied to measure ET and tree sap flow of the endemic yellow cypress (Chamaecyparis obtusa var. formosana). ET was 553 mm yr?1 over the study period with an annual rainfall and fog deposition of 4893 and 288 mm yr–1, respectively. The duration of canopy wetness exceeded actual fog or rain events (mostly in the afternoon), and the intercepted water was evaporated later in the following dry morning. The cumulative wet duration accounted for 52% of time over the study period, which was longer than the duration of rainfall and fog altogether (41%). As it adapted to the extremely moist environment, the yellow cypress behaved in a wet‐enhanced/dry‐reduced water use strategy and was sensitive to short periods of dry atmosphere with high evaporation potential. During dry days, the sap flow rate rose quickly after dawn and led to conservative water use through midday and the afternoon. During periodically wet days, the canopy was mostly wetted in the morning, and the interception evaporation contributed largely to the morning ET. The initiation of morning sap flow was postponed 1–3 h, and the sap flow rate tended to peak later at midday. The midday canopy conductance was higher in the periodically wet days (10.6 mm s–1) as compared with 7.6 mm s?1 in the dry days. Consequently, the dry‐reduced water use strategy led to much lower annual ET with respect to the available energy (~46%) and high precipitation input (~11%). The moist‐adapted ecohydrology we report reveals the vulnerability of montane cloud forests to prolonged fog‐free periods. More research is urgently needed to better understand the resilience of these ecosystems and formulate adaptive management plans. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

13.
The quantification of the various components of hydrological processes in a watershed remains a challenging topic as the hydrological system is altered by internal and external drivers. Watershed models have become essential tools to understand the behaviour of a catchment under dynamic processes. In this study, a physically based watershed model called Soil Water Assessment Tool was used to understand the hydrologic behaviour of the Upper Tiber River Basin, Central Italy. The model was successfully calibrated and validated using observed weather and flow data for the period of 1963–1970 and 1971–1978, respectively. Eighteen parameters were evaluated, and the model showed high relative sensitivity to groundwater flow parameters than the surface flow parameters. An analysis of annual hydrological water balance was performed for the entire upper Tiber watershed and selected subbasins. The overall behaviour of the watershed was represented by three categories of parameters governing surface flow, subsurface flow and whole basin response. The base flow contribution has shown that 60% of the streamflow is from shallow aquifer in the subbasins. The model evaluation statistics that evaluate the agreement between the simulated and the observed streamflow at the outlet of a watershed and other three different subbasins has shown a coefficient of determination (R2) from 0.68 to 0.81 and a Nash–Sutcliffe efficiency (ENS) between 0.51 and 0.8 for the validation period. The components of the hydrologic cycle showed variation for dry and wet periods within the watershed for the same parameter sets. On the basis of the calibrated parameters, the model can be used for the prediction of the impact of climate and land use changes and water resources planning and management. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

14.
Abandoned underground mines (AUM) have caused dramatic environmental effects that are closely linked to regional sustainability. This paper explores the potential hydrological impact of AUM in the Monday Creek Watershed, a typically mined area in Appalachian region, using the Soil and Water Assessment Tool (SWAT 2005) model and Sequential Uncertainty Fitting (SUFI‐2), calibrated at both the global and local scales. The locally calibrated model better incorporates those key parameters relevant to AUM for specific sub‐basins and hydrologic response units. Data from the years 2003–2004 were used for calibration and 2005–2006 for validation. The results were quite satisfactory; both the coefficient of determination (R2) and the Nash–Sutcliffe efficiency statistic were over 0.80. The potential influences of AUM were assessed by modelling an alternative scenario assuming no AUM for the period 2003–2009. Results show that the hydrological process of lateral subsurface flow plays a dominant role in linking AUM to overall watershed hydrology. The potential hydrological impact of AUM is an increased annual lateral flow of 82.1%, and a decrease in annual surface flow by 15%, leading to an increase of 16.9% in annual water yield for the Monday Creek Watershed. The seasonal fluctuation of water yield has a similar trend to lateral flow, decreasing from March to August and increasing from August to January. Higher volume, higher flow peaks and higher recession constants characterized the hydrograph of daily streamflow from AUM. The results indicate that more emphasis should be put on lateral flow for further study of acid mine drainage and flooding control in those watersheds with AUM. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

15.
An increasing impervious area is quickly extending over the Wu‐Tu watershed due to the endless demands of the people. Generally, impervious paving is a major result of urbanization and more recently has had the potential to produce more enormous flood disasters than those of the past. In this study, 40 available rainfall–runoff events were chosen to calibrate the applicable parameters of the models and to determine the relationships between the impervious surfaces and the calibrated parameters. Model inputs came from the outcomes of the block kriging method and the non‐linear programming method. In the optimal process, the shuffled complex evolution method and three criteria were applied to compare the observed and simulated hydrographs. The tendencies of the variations of the parameters with their corresponding imperviousness were established through regression analysis. Ten cases were used to examine the established equations of the parameters and impervious covers. Finally, the design flood routines of various return periods were furnished through use of approaches containing a design storm, block kriging, the SCS model, and a rainfall‐runoff model with established functional relationships. These simulated flood hydrographs were used to compare and understand the past, present, and future hydrological conditions of the watershed studied. In the research results, the time to peak of flood hydrographs for various storms was diminished approximately from 11 h to 6 h in different decrements, whereas peak flow increased respectively from 127 m3 s?1 to 629 m3 s?1 for different storm intensities. In addition, this study provides a design diagram for the peak flow ratio to help engineers and designers to construct hydraulic structures efficiently and prevent possible damage to human life and property. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

16.
Abstract

Discharge characteristics and the role of monsoonal rainfall in the glacierized Dokriani catchment in the Ganga River headwaters, Garhwal Himalaya, India are examined for the summer ablation period of 1994. Monsoonal rainfall over the glacierized area appears to be an important factor controlling the characteristics of the discharge hydrograph. Monsoonal cloud cover reduces the energy input resulting in subdued ice melt. The monsoonal component was separated from the bulk flow hydrograph recorded close to the glacier snout using a mass balance approach: 11.46% of the total discharge of 62.38 x l06 m3 was contributed by the rainfall over the catchment.  相似文献   

17.
Abstract

This study presents an analysis of three hydrological years (2007/08, 2008/09 and 2009/10) of precipitation, runoff and sediment yield collected from a small (669.7 ha) semi-arid watershed in southeastern Spain (Lanjarón). At the watershed outlet the runoff, suspended sediment concentration, total solute concentrations and dissolved nutrients (N-NO3, N-NH4, H2PO4 and K) in streamflow were continuously monitored. The runoff was highly variable, ranging between 53.4 and 154.7 mm year?1, with an average of 97.6 mm year?1. In contrast, sediment yields were more regular, averaging 1.8 Mg ha?1 year?1. The hydrological response of the watershed depended mainly on rainfall intensity. Formerly, 32% of the watershed was forested and runoff was more regular, despite the typical Mediterranean rainfall cycle; however, due to forest area reduction to 17% and the increase in abandoned farmland area (18%) in recent decades, the runoff variability has increased. Greater amounts of solutes (32.7 Mg ha?1 year?1) were exported, so that this water is considered as poor for irrigation use. The temporal nutrient export was related to seasonal discharge fluctuations as well as daily concentrations. In addition, the nutrient concentrations of the water discharged were lower than threshold limits cited in water-quality standards for agricultural use and for potable water, with the exception of K (65.9 mg L?1), which may degrade surface waters as well as irrigated soils. Thus, hydrological and erosive processes depended on the watershed features, but also on prior conditions in combination with the characteristics of rainfall episodes.

Citation Durán, Z.V.H., Francia, M.J.R., Garcia, T.I., Rodríguez, P.C.R., Martínez, R.A., and Cuadros, T.S., 2012. Runoff and sediment yield from a small watershed in southeastern Spain (Lanjarón): implications for water quality. Hydrological Sciences Journal, 57 (8), 1610–1625.  相似文献   

18.
Abstract

This paper describes the use of a simple two stage rainfall-runoff model in which a curve number (CN) principle is used to calculate the soil water content and, subsequently, the rainfall contribution to direct runoff and groundwater flow. The maximum soil water retention, S, is used to express various characteristics of a catchment (infiltration rate, soil cover and land use, as in the CN method) relevant to flood formation. Using historical flood events, the model is calibrated, and the statistical distribution parameters of peak flows determined. With the same historical input data scenarios (rainfall), sets of flood hydrographs are simulated for various values of the parameter S, and corresponding distribution parameters of peak flows are determined. This procedure is used to demonstrate possible changes in flood regime to be expected due to changes of the catchment soil properties and its vegetation cover. A case study is presented for the River Hron catchment, area 582 km2, in the mountainous region of central Slovakia.  相似文献   

19.
This work proposes a risk analysis model to evaluate the risk of underestimating the predicted peak discharge, i.e. the exceedance of probability due to the uncertainties in rainfall information (rainfall depth, duration, and storm pattern) and the parameters of the rainfall-runoff model (Sacramento Soil Moisture Accounting model, SAC-SMA) during the flooding prevention and warning operation. The proposed risk analysis model is combined with the multivariate Monte Carlo simulation method and the Advance First-Order Second-Moment method (AFOSM). The observed rainfall and discharge measured at Yu-feng Basin study area in Shihmen reservoir watershed is used in the model development and application. The results of the model application indicate that the proposed risk analysis model can analyze the sensitivity of the uncertainty factors for the predicted peak discharge and evaluates the variation of the probability of exceeding the predicted peak discharge with respect to the rainfall depth and storm duration. In addition, the result of risk analysis for a real rainstorm event, Typhoon Morakot, shows that the proposed model successfully explores the risk of underestimating the predicted peak discharge using SAC-SMA and forecasted rainfall information and provides a probabilistic forecast of the peak discharge.  相似文献   

20.
Two tracer experiments have been carried out at an enclosed catchment in southern Norway. The catchment was brought to steady state with respect to rainfall and runoff prior to the tracer addition. A known concentration of lithium bromide was then added to the rainfall for the duration of each event. The tight control on tracer concentration and rainfall amount enabled assessment of the contribution of old and new water to runoff, the dominant flow pathways and soil water residence times during a storm event. A significant volume of ‘old’ water contributes to runoff despite the hydrologically responsive nature of the catchment and several hours of tracer injected rainfall are required before ‘new’ water becomes the dominant runoff source. After 34 h of tracer injection, ‘new’ water apparently contributes c. 83% to instantaneous flow and c. 55% of the total tracer input to the catchment has been lost in runoff. Recovery of the tracer from soil water indicates that the organic soil surface layer is the dominant flow pathway for rainwater through the catchment and that a significant pathway also exists at the soil–bedrock interface. New water is retained in deep pockets of soil for several days. Assessment of the conservative behaviour of the tracer suggests that 10–14% of the input Br− is retained in the soil and the tracer is not conservative. Laboratory experiments indicate that sorption of Br− to organic soil is the likely mechanism of retention. This process is probably concentration dependent and will have occurred predominantly during the initial period of tracer application. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

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