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1.
Low Impact Development (LID) aims to mitigate the hydrological impacts of urbanization by replication of processes in natural catchments. Green roofs covered with vegetation and pervious substrate are one alternative among a wide range of LID tools. Water retention of green roofs depends on many factors (e.g. local climate), and measurements remain crucial in evaluating their performance. The simulation of green roof retention by a hydrological model is one option to evaluate their potential benefits before implementation. In this paper, we evaluated the ability of the recently introduced LID green roof module of the stormwater management model to replicate runoff from monitored green roof test beds under Nordic climate conditions. A parameter sensitivity analysis was conducted to identify calibration parameters. The model showed an overall acceptable performance, and the results indicated the importance of accurately estimating potential evapotranspiration rates for inter‐event periods, which is essential in representing the retention capacity regeneration. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

2.
Sustainable strategies such as green roofs have been implemented as stormwater management tools to mitigate disturbance of the hydrologic cycle resulting from urbanization. Green roofs, also referred to as vegetated roofs, can improve the urban landscape by reducing heat island effects, providing ecosystem services, and facilitating the retention and treatment of stormwater. Green roofs have received particular attention because they do not require acquisition and development of land and represent an application of biomimicry in design and construction. In this paper, we evaluate the effects of precipitation, evapotranspiration (ET), antecedent dry period (ADP), and seasonal variation on the run‐off quantity and distribution of an extensive, sedum covered, green roof on a commercial building in Syracuse, NY, USA. The green roof greatly facilitated retention of precipitation events without significant changes over the 4‐year study. The green roof retained on average 95.9 ± 3.6% (6.5 ± 5.6 mm) per rainfall event, with a range from 75% to 99.6% (33.2 to 3.3 mm). However, as precipitation quantity increased, the retention of water decreased. This high water retention capacity was the result of the combined effects of ET, stormwater storage (plants, growth media, and stormwater retention layer), and limited surface run‐off from the roof deck due to variation in the sloping of the green roof and the tapered insulation to the deck drains. The water retention capacity of the green roof did not change significantly between growing and nongrowing seasons. Slightly greater precipitation during the growing season coincided with increased ET. Average potential ET during the growing season was approximately 3 times greater than during the nongrowing season. The hydrologic performance of the green roof was not significantly impacted by an ADP greater than 2 days.  相似文献   

3.
Rainfall retention and runoff detention are likely the most important ecosystem services provided by extensive green roofs (EGRs) that contribute to urban stormwater mitigation and management. However, the hydrological performance and runoff generation mechanisms of mature, well-established EGRs in tropical regions remain poorly understood. This study evaluated the rainfall retention, discharge detention times and processes of runoff generation in two neighbouring 20-year-old EGRs with different slopes (2° and 14° for EGRns and EGRws, respectively) and management practices in Mexico City; results were compared with those obtained in a conventional roof (CR, 2° slope). Precipitation, substrate moisture and storm runoff were continuously measured during the 2017 and 2018 rainy seasons (May–November). Results showed spatial differences in substrate properties and moisture within and between green roofs. In general, higher bulk densities and a wide range of variation in water content characterized the bare substrate areas compared to those below vegetation. Greatest increases in substrate moisture and storm runoff were observed in the steeper green roof. Subsurface flow was the dominant process controlling the amount and timing of stormflow in the EGRs. The occurrence of saturation excess overland flow was small and detected when large rain events were preceded by high wetness conditions. The main factors influencing the hydrological responses of the green roofs were their substrate hydrophysical properties, related mostly to vegetation cover, management and age, and to much lesser extent to slope and substrate depth. On average, rainfall retention was ~60% in the EGRs with significantly longer delays and prolonged runoff times (100 and 340 min, respectively) compared to CR (3%, 20 min, and 258 min, respectively). Overall, these findings highlight the potential of EGRs in reducing stormflow and peak discharges for most rainfall in Mexico City, and thus mitigating the risk of saturation and overflow of urban drainages.  相似文献   

4.
The urban environment modifies the hydrologic cycle resulting in increased runoff rates, volumes, and peak flows. Green infrastructure, which uses best management practices (BMPs), is a natural system approach used to mitigate the impacts of urbanization onto stormwater runoff. Patterns of stormwater runoff from urban environments are complex, and it is unclear how efficiently green infrastructure will improve the urban water cycle. These challenges arise from issues of scale, the merits of BMPs depend on changes to small‐scale hydrologic processes aggregated up from the neighborhood to the urban watershed. Here, we use a hyper‐resolution (1 m), physically based hydrologic model of the urban hydrologic cycle with explicit inclusion of the built environment. This model represents the changes to hydrology at the BMP scale (~1 m) and represents each individual BMP explicitly to represent response over the urban watershed. Our study varies both the percentage of BMP emplacement and their spatial location for storm events of increasing intensity in an urban watershed. We develop a metric of effectiveness that indicates a nonlinear relationship that is seen between percent BMP emplacement and storm intensity. Results indicate that BMP effectiveness varies with spatial location and that type and emplacement within the urban watershed may be more important than overall percent.  相似文献   

5.
In order to investigate the hydrologic response of a green roof system within the urban environment, a monitoring campaign is carried out at the green roof site of the University of Genova (Italy). Experimental data confirm that the green roof is able to significantly mitigate the generation of runoff with median values of retained volume and peak reduction, respectively, equal to 94 and 98%. A conceptual linear reservoir and a simple mechanistic (Hydrus‐1D) models are implemented to simulate the hydrologic behaviour of the system; each model is calibrated and validated based on experimental data collected at the green roof site. The hydrographs simulated with both hydrologic models reproduce with acceptable matching capabilities the experimental measurements, as confirmed by the Nash‐Sutcliffe Efficiency index generally greater than 0·60. Although the relative percentage differences evaluated for the selected hydrograph variables (the total effluent volume, the peak flow rate and the hydrograph centroid) demonstrate that the mechanistic model is more accurate, prediction errors of the conceptual model are generally limited when compared with the observed hydrologic performance. Results of the present comparison are useful in supporting conceptual model selection in case the hydrologic response is addressed for hydrologic performance assessment. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

6.
An event‐based model is used to investigate the impact of the spatial distribution of imperviousness on the hydrologic response of a basin characterized by an urban land use. The impact of the spatial distribution of imperviousness is investigated by accounting for its location within the basin when estimating the generated runoff and the hydrologic response. The event model accounts for infiltration and saturation excess; the excess runoff is routed to the outlet using a geomorphologic unit hydrograph. To represent the spatial distribution of rainfall and imperviousness, radar and remotely derived data are used, respectively. To estimate model parameters and analyse their behaviour, a split sample test and parameter sensitivity analysis are performed. From the analysis of parameters, we found the impervious cover tends to increase the sensitivity and storm dependency of channel routing parameters. The calibrated event model is used to investigate the impact of the imperviousness gradient by estimating and comparing hydrographs at internal locations in the basin. From this comparison, we found the urban land use and the spatial variability of rainfall can produce bigger increases in the peak flows of less impervious areas than the most urbanized ones in the basin. To examine the impacts of the imperviousness pattern, scenarios typifying extreme cases of sprawl type and clustered development are used while accounting for the uncertainty in parameters and the initial condition. These scenarios show that the imperviousness pattern can produce significant changes in the response at the main outlet and at locations internal to the overall watershed. Overall, the results indicate the imperviousness pattern can be an influential factor in shaping the hydrologic response of an urbanizing basin. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

7.
Less attention has been paid to runoff generation from semi-arid than from humid-temperate catchments. The SCS curve number approach is simple to apply and widely used, but lacks physical underpinning. Here output from a runoff generation models is compared with data from field measurements, making use of 11 years data from rainfall and runoff events at the Sierra de Enguera Soil Erosion Experimental Station in Eastern Spain. Runoff from natural rainfall events was monitored for 10 years on bare plots of 1–16 m length. The largest storm event was of 142 mm, generating runoff of up to 115 mm on the smallest plots. The model presented simulates overland storm flow on a sloping rough and unvegetated surface, representing an area of 320 × 320 m. Green-Ampt infiltration constants are randomly assigned to each cell in a 128 × 128 grid, and rectangular storms applied at a range of total amounts and intensities to simulate runoff at each transect across the area. A simple algebraic expression is developed to estimate total runoff and storage in terms of storm size and duration, and plot length, with parameters that reflect infiltration behaviour, and this expression is compared with the SCS curve number approach. For the very largest storms, both expressions converge asymptotically towards 100% runoff, but the revised expression greatly improves estimates of runoff from smaller events. Output of these simulations is compared with measured storm runoff data on bare runoff plots at the Sierra de Enguera experimental Station in SE Spain and gives further support to the proposed expression for storm runoff.  相似文献   

8.
Biochar has the potential to be a soil amendment in green roofs owing to its water retention, nutrient supply, and carbon sequestration application. The combined effects of biochar and vegetated soil on hydraulic performance (e.g., saturated hydraulic conductivity, retention and detention, and runoff delay) are the crucial factor for the application of the novel biochar in green roofs. Recent studies investigated soil water potential (i.e., suction) either on vegetated soil or on biochar-amended soil but rarely focused on their integrated application. With the purpose of investigating the hydraulic performance of green roofs in the application of biochar, the combined effect of biochar and vegetated soil on hydrological processes was explored. Artificial rainfall experiments were conducted on the four types of experimental soil columns, including natural soil, biochar-amended soil, vegetated natural soil, and vegetated biochar-amended soil. The surface ponding, bottom drainage and the volumetric water content were measured during the rainfall test. Simulation method by using HYDRUS-1D was adopted for estimating hydraulic parameters and developing modelling analysis. The results indicated that the saturated hydraulic conductivity of vegetated soil columns were higher than bare soil columns. The addition of biochar decreased the saturated hydraulic conductivity, and the magnitude of decrease was much significant in the case of vegetated soil. The influence of vegetation on permeability is more prominent than biochar. The vegetated biochar-amended soil has the highest retention and detention capacity, and shows a preferable runoff delay effect under heavy rain among the four soil columns. The results from the present study help to understand the hydrological processes in the green roof in the application of biochar, and imply that biochar can be an alternative soil amendment to improve the hydraulic performance.  相似文献   

9.
Using water budget data from published literature, we demonstrate how hydrologic processes govern the function of various stormwater infrastructure technologies. Hydrologic observations are displayed on a Water Budget Triangle, a ternary plot tool developed to visualize simplified water budgets, enabling side‐by‐side comparison of green and grey approaches to stormwater management. The tool indicates ranges of hydrologic function for green roofs, constructed wetlands, cisterns, bioretention, and other stormwater control management structures. Water budgets are plotted for several example systems to provide insight on structural and environmental design factors, and seasonal variation in hydrologic processes of stormwater management systems. Previously published water budgets and models are used to suggest appropriate operational standards for several green and grey stormwater control structures and compare between conventional and low‐impact development approaches. We compare models, characterize and quantify water budgets and expected ranges for green and grey infrastructure systems, and demonstrate how the Water Budget Triangle tool may help users to develop a data‐driven approach for understanding design and retrofit of green stormwater infrastructure.  相似文献   

10.
Distributed, continuous hydrologic models promote better understanding of hydrology and enable integrated hydrologic analyses by providing a more detailed picture of water transport processes across the varying landscape. However, such models are not widely used in routine modelling practices, due in part to the extensive data input requirements, computational demands, and complexity of routing algorithms. We developed a two‐dimensional continuous hydrologic model, HYSTAR, using a time‐area method within a grid‐based spatial data model with the goal of providing an alternative way to simulate spatiotemporally varied watershed‐scale hydrologic processes. The model calculates the direct runoff hydrograph by coupling a time‐area routing scheme with a dynamic rainfall excess sub‐model implemented here using a modified curve number method with an hourly time step, explicitly considering downstream ‘reinfiltration’ of routed surface runoff. Soil moisture content is determined at each time interval based on a water balance equation, and overland and channel runoff is routed on time‐area maps, representing spatial variation in hydraulic characteristics for each time interval in a storm event. Simulating runoff hydrographs does not depend on unit hydrograph theory or on solution of the Saint Venant equation, yet retains the simplicity of a unit hydrograph approach and the capability of explicitly simulating two‐dimensional flow routing. The model provided acceptable performance in predicting daily and monthly runoff for a 6‐year period for a watershed in Virginia (USA) using readily available geographic information about the watershed landscape. Spatial and temporal variability in simulated effective runoff depth and time area maps dynamically show the areas of the watershed contributing to the direct runoff hydrograph at the outlet over time, consistent with the variable source area overland flow generation mechanism. The model offers a way to simulate watershed processes and runoff hydrographs using the time‐area method, providing a simple, efficient, and sound framework that explicitly represents mechanisms of spatially and temporally varied hydrologic processes. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

11.
Recent advances have been made to modernize estimates of probable precipitation scenarios; however, researchers and engineers often continue to assume that rainfall events can be described by a small set of event statistics, typically average intensity and event duration. Given the easy availability of precipitation data and advances in desk‐top computational tools, we suggest that it is time to rethink the ‘design storm’ concept. Design storms should include more holistic characteristics of flood‐inducing rain events, which, in addition to describing specific hydrologic responses, may also be watershed or regionally specific. We present a sensitivity analysis of nine precipitation event statistics from observed precipitation events within a 60‐year record for Tompkins County, NY, USA. We perform a two‐sample Kolmogorov–Smirnov (KS) test to objectively identify precipitation event statistics of importance for two related hydrologic responses: (1) peak outflow from the Six Mile Creek watershed and (2) peak depth within the reservoir behind the Six Mile Creek Dam. We identify the total precipitation depth, peak hourly intensity, average intensity, event duration, interevent duration, and several statistics defining the temporal distribution of precipitation events to be important rainfall statistics to consider for predicting the watershed flood responses. We found that the two hydrologic responses had different sets of statistically significant parameters. We demonstrate through a stochastic precipitation generation analysis the effects of starting from a constrained parameter set (intensity and duration) when predicting hydrologic responses as opposed to utilizing an expanded suite of rainfall statistics. In particular, we note that the reduced precipitation parameter set may underestimate the probability of high stream flows and therefore underestimate flood hazard. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

12.
hydrologic models are important tools to estimate runoff from a catchment. Identification of broad based parameters of a hydrologic model for development of direct runoff hydrograph is a key issue for the modelers. Optimization and regionalization of hydrologic parameters for application of Nash’s model is investigated in this paper. Six catchments dominated by hill torrent flows were selected for this purpose. Fifty seven rainfall events were used for regionalization of parameters and about 55 events were used for validation of the results. The hydrologic parameters of the Nash Model, number of linear cascades (N) and storage coefficient (k) were determined using optimization based upon Downhill Simplex method. The data was collected by field measurements and from Water and Power Development Authority (WAPDA) Pakistan. The physical parameters of the catchments were derived from the satellite images of the watersheds with the help of ERDAS software. The performance of the model was assessed by the model efficiency. It is concluded that the conceptual Nash model can simulate direct runoff hydrograph using regional hydrologic parameters with model efficiency of 67%.  相似文献   

13.
Hydrologic responses to variations in storm direction provide useful information for the analysis and prediction of floods and the development of watershed management strategies. However, the prediction of hydrologic responses to changes in storm direction is a difficult task that requires meteorological simulations and extensive computation. It is also difficult to identify the center of rotation of a storm affecting a basin of interest. Therefore, we propose a simple approach of rotating the basin position relative to the storm within the rainfall–runoff simulation model instead of changing the pathway of the storm, which we term the basin rotation method (BRM). The proposed BRM was tested on four major typhoon events in South Korea. The results illustrated that the original basin orientation (i.e., before it was rotated) exhibits earlier and higher peak discharge and earlier recession compared to the basin after rotation. We conclude that the proposed method (BRM) is a viable alternative for use in assessing the directional influence of moving storms on floods caused by historical rather than hypothetical storm events.  相似文献   

14.
In the face of increasing urbanization, there is growing interest in application of microscale hydrologic solutions to minimize storm runoff and conserve water at the source. In this study, a physically based numerical model was developed to understand hydrologic processes better at the urban residential scale and the interaction of these processes among different best management practices (BMPs). This model simulates hydrologic processes using an hourly interval for over a full year or for specific storm events. The model was applied to treatment and control single‐family residential parcels in Los Angeles, California. Data collected from the control and treatment sites over 2 years were used to calibrate and validate the model. Annual storm runoff to the street was eliminated by 97% with installation of rain gutters, a driveway interceptor, and lawn retention basin. Evaluated individually, the driveway interceptor was the most effective BMP for storm runoff reduction (65%), followed by the rain gutter installation (28%), and lawn converted to retention basin (12%). An 11 m3 cistern did not substantially reduce runoff, but provided 9% of annual landscape irrigation demand. Simulated landscape irrigation water use was reduced 53% by increasing irrigation system efficiency, and adjusting application rates monthly based on plant water demand. The model showed that infiltration and surface runoff processes were particularly sensitive to the soil's physical properties and its effective depth. Replacing the existing loam soil with clay soil increased annual runoff discharge to the street by 63% when climate and landscape features remained unchanged. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

15.
In this paper, we analyse how the performance and calibration of a distributed event‐based soil erosion model at the hillslope scale is affected by different simplifications on the parameterizations used to compute the production of suspended sediment by rainfall and runoff. Six modelling scenarios of different complexity are used to evaluate the temporal variability of the sedimentograph at the outlet of a 60 m long cultivated hillslope. The six scenarios are calibrated within the generalized likelihood uncertainty estimation framework in order to account for parameter uncertainty, and their performance is evaluated against experimental data registered during five storm events. The Nash–Sutcliffe efficiency, percent bias and coverage performance ratios show that the sedimentary response of the hillslope in terms of mass flux of eroded soil can be efficiently captured by a model structure including only two soil erodibility parameters, which control the rainfall and runoff production of suspended sediment. Increasing the number of parameters makes the calibration process more complex without increasing in a noticeable manner the predictive capability of the model. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
Influence of rainfall spatial variability on flood prediction   总被引：9，自引：0，他引：9  
This paper deals with the sensitivity of distributed hydrological models to different patterns that account for the spatial distribution of rainfall: spatially averaged rainfall or rainfall field. The rainfall data come from a dense network of recording rain gauges that cover approximately 2000 km2 around Mexico City. The reference rain sample accounts for the 50 most significant events, whose mean duration is about 10 h and maximal point depth 170 mm. Three models were tested using different runoff production models: storm-runoff coefficient, complete or partial interception. These models were then applied to four fictitious homogeneous basins, whose sizes range from 20 to 1500 km2. For each test, the sensitivity of the model is expressed as the relative differences between the empirical distribution of the peak flows (and runoff volumes), calculated according to the two patterns of rainfall input: uniform or non-uniform. Differences in flows range from 10 to 80%, depending on the type of runoff production model used, the size of the basin and the return period of the event. The differences are generally moderate for extreme events. In the local context, this means that uniform design rainfall combining point rainfall distribution and the probabilistic concept of the areal reduction factor could be sufficient to estimate major flood probability. Differences are more significant for more frequent events. This can generate problems in calibrating the hydrological model when spatial rainfall localization is not taken into account: a bias in the estimation of parameters makes their physical interpretation difficult and leads to overestimation of extreme flows.  相似文献   

17.
We report an empirical analysis of the hydrologic response of three small, highly impervious urban watersheds to pulse rainfall events, to assess how traditional stormwater management (SWM) alters urban hydrographs. The watersheds vary in SWM coverage from 3% to 61% and in impervious cover from 45% to 67%. By selecting a set of storm events that involved a single rainfall pulse with >96% of total precipitation delivered in 60 min, we reduced the effect of differences between storms on hydrograph response to isolate characteristic responses attributable to watershed properties. Watershed-average radar rainfall data were used to generate local storm hyetographs for each event in each watershed, thus compensating for the extreme spatial and temporal heterogeneity of short-duration, intense rainfall events. By normalizing discharge values to the discharge peak and centring each hydrograph on the time of peak we were able to visualize the envelope of hydrographs for each group and to generate representative composite hydrographs for comparison across the three watersheds. Despite dramatic differences in the fraction of watershed area draining to SWM features across these three headwater tributaries, we did not find strong evidence that SWM causes significant attenuation of the hydrograph peak. Hydrograph response for the three watersheds is remarkably uniform despite contrasts in SWM, impervious cover and spatial patterns of land cover type. The primary difference in hydrograph response is observed on the recession limb of the hydrograph, and that change appears to be associated with higher storm-total runoff in the watersheds with more area draining to SWM. Our findings contribute more evidence to the work of previous authors suggesting that SWM is less effective at attenuating urban hydrographs than is commonly assumed. Our findings also are consistent with previous work concluding that percent impervious cover may have greater influence on runoff volume than percent SWM coverage.  相似文献   

18.
Abstract

A relatively simple process-oriented, physically-based distributed (PBD) hydrological model, the distributed runoff and erosion assessment model (DREAM), is described, and a validation study conducted in the semi-forested watershed of Pathri Rao, in the Garhwal Himalayas, India, is reported. DREAM takes account of watershed heterogeneity as reflected by land use, soil type, topography and rainfall, measured in the field or estimated through remote sensing, and generates estimates of runoff and sediment yield in spatial and temporal domains. The model is based on simultaneous solution of flow dynamics, based on kinematic wave theory, followed by solution of soil erosion dynamics. As the storm rainfall proceeds, the process of overland flow generation is dependent on the interception storage and infiltration rates. The components of the soil erosion model have been modified to provide better prediction of sediment flow rates and sediment yields. The validation study conducted to test the performance of the model in simulating soil erosion and sediment yield during different storm events monitored in the study watershed showed that the model outputs are satisfactory. Details of a sensitivity analysis, model calibration and the statistical evaluation of the results obtained are also presented and discussed. It is noteworthy that the distributed nature of the model combined with the use of geographical information system (GIS) techniques permits the computation and representation of the spatial distribution of sediment yield for simulated storm events, and a map of the spatial distribution of sediment yield for a simulated storm event is presented to highlight this capability.

Citation Ramsankaran, R., Kothyari, U.C., Ghosh, S.K., Malcherek, A., and Murugesan, K., 2013. Physically-based distributed soil erosion and sediment yield model (DREAM) for simulating individual storm events. Hydrological Sciences Journal, 58 (4), 872–891.  相似文献   

19.
The need for accurate hydrologic analysis and rainfall–runoff modelling tools has been rapidly increasing because of the growing complexity of operational hydrologic and hydraulic problems associated with population growth, rapid urbanization and expansion of agricultural activities. Given the recent advances in remote sensing of physiographic features and the availability of near real‐time precipitation products, rainfall–runoff models are expected to predict runoff more accurately. In this study, we compare the performance and implementation requirements of two rainfall–runoff models for a semi‐urbanized watershed. One is a semi‐distributed conceptual model, the Hydrologic Engineering Center‐Hydrologic Modelling System (HEC‐HMS). The other is a physically based, distributed‐parameter hydrologic model, the Gridded Surface Subsurface Hydrologic Analysis (GSSHA). Four flood events that took place on the Leon Creek watershed, a sub‐watershed of the San Antonio River basin in Texas, were used in this study. The two models were driven by the Multisensor Precipitation Estimator radar products. One event (in 2007) was used for HEC‐HMS and GSSHA calibrations. Two events (in 2004 and 2007) were used for further calibration of HEC‐HMS. Three events (in 2002, 2004 and 2010) were used for model validation. In general, the physically based, distributed‐parameter model performed better than the conceptual model and required less calibration. The two models were prepared with the same minimum required input data, and the effort required to build the two models did not differ substantially. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

20.
Physiography and land cover determine the hydrologic response of watersheds to climatic events. However, vast differences in climate regimes and variation of landscape attributes among watersheds (including size) have prevented the establishment of general relationships between land cover and runoff patterns across broad scales. This paper addresses these difficulties by using power spectral analysis to characterize area‐normalized runoff patterns and then compare these patterns with landscape features among watersheds within the same physiographic region. We assembled long‐term precipitation and runoff data for 87 watersheds (first to seventh order) within the eastern Piedmont (USA) that contained a wide variety of land cover types, collected environmental data for each watershed, and compared the datasets using a variety of statistical measures. The effect of land cover on runoff patterns was confirmed. Urban‐dominated watersheds were flashier and had less hydrologic memory compared with forest‐dominated watersheds, whereas watersheds with high wetland coverage had greater hydrologic memory. We also detected a 10–15% urban threshold above which urban coverage became the dominant control on runoff patterns. When spectral properties of runoff were compared across stream orders, a threshold after the third order was detected at which watershed processes became dominant over precipitation regime in determining runoff patterns. Finally, we present a matrix that characterizes the hydrologic signatures of rivers based on precipitation versus landscape effects and low‐frequency versus high‐frequency events. The concepts and methods presented can be generally applied to all river systems to characterize multiscale patterns of watershed runoff. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

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