Article

Regional Flow-Duration Curves: Reliability for Ungauged Basins

October 2004
Advances in Water Resources 27(10):953-965

DOI:10.1016/j.advwatres.2004.08.005

Authors:

Attilio Castellarin

University of Bologna

Giorgio Galeati

Luigia Brandimarte

KTH Royal Institute of Technology

Alberto Montanari

University of Bologna

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A flow-duration curve (FDC) illustrates the relationship between the frequency and magnitude of streamflow. Applications of FDC are of interest for many hydrological problems related to hydropower generation, river and reservoir sedimentation, water quality assessment, water-use assessment, water allocation and habitat suitability. This study addresses the problem of FDC estimation for ungauged river basins, assessing the effectiveness and reliability of several regional approaches. The study refers to a wide region of eastern central Italy and adopts a jack-knife cross-validation procedure to evaluate the uncertainty of regional FDC’s, comparing it with the uncertainty of empirical FDC’s constructed from short samples of streamflow data. The results (a) provide an evaluation of the reliability of the regional FDC’s for ungauged sites, (b) show that the reliability of the three best performing regional models are similar to one another, and (c) demonstrate that empirical FDC’s based on limited data samples generally provide a better fit of the long-term FDC’s than regional FDC’s.

Advancing low-flow quantile estimation: The role of areal scale factor (ASF) and annual flow–duration curves

Article

Full-text available

Jan 2024

Estimating the streamflow corresponding to a particular probability is of great importance in many hydrological studies, such as determining hydroelectric water potential, assessing water quality, and investigating sedimentation and drought. This paper aims to effectively estimate low-flow quantiles since hydrologic droughts motivate the study. The study illustrates a methodology, where droughts are characterized by the lower part of the flow–duration curve (FDC), and offers a perspective estimating low-flow quantiles related to the basin characteristics. Low-flow quantiles are derived both from traditional FDCs curves and median annual FDCs (AFDCs). As an innovation, the concept of areal scale factor, which represents a scaling ratio between the basin area and flow quantiles, was introduced. Unlike many other parametric approaches, this study models the streamflow quantiles depending on the basin characteristics instead of the parameters in the analytical equation of FDCs. The methodology was evaluated for the Western and Southwestern Anatolia regions in Turkey. The outcomes were compared for two types of FDCs in two regions. The approach gave similar results for both study regions. AFDCs provided a distinct advantage over traditional FDCs, especially for low-flow quantiles, due to the superiority of AFDCs in estimating streamflow quantiles of intermittent streams.

Regionalization of flow duration curves for catchments in southern India using a hierarchical cluster approach

Article

Full-text available

Dec 2023

The present study on the hydrologic regionalization was taken up to evaluate the utility of hierarchical cluster analysis for the delineation of hydrologically homogeneous regions and multiple linear regression (MLR) models for information transfer to derive flow duration curve (FDC) in ungauged basins. For this purpose, 50 catchments with largely unregulated flows located in South India were identified and a dataset of historical streamflow records and 16 catchment attributes was created. Using selected catchment attributes, three hydrologically homogenous regions were delineated using a hierarchical agglomerative cluster approach, and nine flow quantiles (10–90%) for each of the catchments in the respective clusters was derived. Regionalization approach was then adopted, whereby using step-wise regression, flow quantiles were related with readily derived basin-physical characteristics through MLR models. Cluster-wise performance analysis of the developed models indicated excellent performance with an average coefficient of determination (R2) values of 0.85, 0.97, and 0.8 for Cluster-1, -2, and -3, respectively, in comparison to poor performance when all 50 stations were considered to be in a single region. However, Jackknife cross-validation showed mixed performances with regard to the reliability of developed models with performance being good for high-flow quantiles and poor for low-flow quantiles.

Regionalizing Streamflow Regime Function through Integrations of Geographical Controls in Mountainous Basins

Article

Full-text available

Jan 2023

Flow duration curves (FDCs) that represent streamflow regime function through an empirical relationship between the FDC parameters and basin descriptors are widely adopted for hydrologic applications. However, the applications of this method are highly dependent on the availability of observation data. Hence, it is still of great significance to explore the process controls of underpinning regional patterns on streamflow regimes. In this study, we developed a new regionalization method of FDCs to solve the problem of runoff prediction for ungauged mountainous basins. Five empirical equations (power, exponential, logarithmic, quadratic, and cubic) were used to fit the observed FDCs in the 64 mountainous basins in eastern China, and the power model outperforms other models. Stepwise regression was used to explore the differentiated control of 23 basin descriptors on the 13 percentile flows of FDCs, and seven descriptors remained as independent variables for further developing the regional FDCs. Application results with different combinations of these selected descriptors showed that five indices, i.e., average annual rainfall (P), average elevation (H), average gradient (β), average topographic index (TI), and maximum 7d of annual rainfall (Max7d), were the main control factors of FDCs in these areas. Through the regional method, we found that 95.31% of all the basins have NSE values greater than 0.60 and ε (namely the relative mean square error) values less than 20%. In conclusion, our study can guide runoff predictions to help manage booming demands for water resources and hydropower developments in mountainous areas.

A parametric approach to estimate streamflow quantiles using annual flow–duration curves

Preprint

Full-text available

May 2022

The flow–duration curve (FDC) is a significant instrument used in solving many hydrological and environmental problems such as evaluating water quality, examining water supply and use for hydroelectric generation and irrigation, and investigating sedimentation and low flows. However, the insufficiency of flow data allows FDCs to be used only for gauged basins or gauged locations in a basin. Therefore, obtaining regional relationships that provide effective estimates about a region, by using the records of existing stations in the region, becomes necessary. This paper illustrates a simple parametric approach, where droughts are characterized by using the lower part of the annual flow–duration curve. The paper uses the actual instantaneous flow data of 30 basins in Western Anatolia and 21 basins in Southwestern Anatolia, Turkey to offer a new perspective for the estimation of streamflow quantiles using Areal Scale Factors ( ASF s), which efficiently represent the relationship between flow quantile and basin area.

A parametric approach to estimate streamflow quantiles using annual flow–duration curves

Preprint

Full-text available

May 2022

A step toward global-scale applicability and transferability of flow duration curve studies: A flow duration curve review (2000–2020)

Article

Sep 2021
J HYDROL

This paper reviews the current status of flow duration curve (FDC) studies that attempt to relate climate and catchment attributes to reproduce or explain the process controls on its shape – toward improving global-scale applicability and transferability of FDC studies. A collection of FDC literature from the past two decades is presented (2000–2020). They are grouped as exemplifying either: (1) studies that develop accurate and reliable prediction tools targeting specific regions and hydro-climate and (2) studies that improve our process understanding across large spatio-temporal scales and domains. We show some of the general characteristics for each group, highlighting some major limitations and advantages. Then, we discuss potential future research directions in the context of improving the global-scale applicability/transferability of FDC studies. Group (1) dominates FDC literature since the inception of FDC. Although some studies have been successfully applied at large spatio-temporal scales, such approaches are often empirical. Thus, they are usually applicable only in the regions of model development, often in hydrologically resourceful countries with densely gaged networks that make it easier to transfer information between catchments. A major impediment to progress is the lack of process input in empirical models, resulting in an inability to generate flexible functions applicable across larger scales. It is from this perspective that process-based approaches are becoming popular among studies in Group (2). Process-based approaches explicitly attempt to identify and understand the process controls on FDC. Thus, they appear more advantageous, although they have yet to be tested at global scales. Furthermore, there are still some contrasting issues regarding the processes that govern FDC shapes. There is a need to develop a general framework for process-based modeling of FDC. Finally, even though much has already been achieved at regional scales through both approaches, the new challenge is to consistently replicate the successes on a global scale.

Hydrology of Lebanese catchments in the Mediterranean context

Thesis

Oct 2015

Merheb Mohammad

Lebanon is a small mountainous country with a typical Mediterranean climate and a high spatial variability of precipitation with a substantial amount occurring as snow. Moreover, the majority of Lebanese terrains are karstic. It is a heavily urbanized country with increasing anthropogenic pressure on water resources. Furthermore, the Lebanese catchments are poorly-gauged due mainly to a large gap of data (1975 - 2000) caused by the civil war (1975 - 1990). However, previous studies on regionalization suggested that across Lebanon when physical characteristics are not changing, hydrologic parameters shows a remarkable degree of spatial coherence. Thus, with an integration of more physical and functional characteristics, a regionalization procedure could be considered as a framework for defining the physical and hydrological characteristics of the Lebanese catchments.Consequently, this work aims to understand the hydrological response characteristics of Lebanese catchments in the Mediterranean context and to classify these catchments according to their physical and hydrological properties. It is structured into three parts: (i) a review on Mediterranean catchments hydrology, (ii) a datal analysis of the Lebanese catchments and comparison to the Mediterranean context, and finally (iii) a classification and modeling of the Lebanese catchments.The first part reviews 152 hydrological studies conducted in the Mediterranean region at various time scales (paper accepted in Hydrological Sciences Journal). This study also compares methods and modeling approaches used for individual-catchment or regionalization studies. The study area is divided into the northwestern (NWM), eastern (EM) and southern (SM) Mediterranean. The analysis indicates regional discrepancies in which the NWM shows the most extreme rainfall regime. A tendency for reduced water resources driven by both anthropogenic and climatic pressures and a more extreme rainfall regime are also noticeable. Catchments show very heterogeneous responses over time and space, resulting in limitations in hydrological modelling and large uncertainties in predictions. However, few models have been developed to address these issues. Regionalization studies are scarce and inconsistent in the Mediterranean. Additional studies are necessary to improve the knowledge of Mediterranean hydrological features and to account for regional specificities.In the second part, an inventory of the available spatial and temporal data was carried out and followed by a detailed data analysis of twenty eight Lebanese catchments through extracting the physical and hydrological response characteristics for the period 2001 – 2011. The spatial data concerns the morphometry, drainage system, geology, karst, soils and land cover. The temporal data concerns the precipitation (32 stations at a daily –when available- and monthly time step), evapotranspiration (remote sensing data at a monthly time step) and discharge data (24 gauging stations at a daily time step and 4 at a monthly time step). Gathering the available temporal data was a real challenge since these data are not always available for the same period and precipitation data is expensive. The 2001 - 2011 temporal data was analyzed and compared with a database from the pre-war period. Afterwards, the hydrological responses of the Lebanese catchments are compared with other Mediterranean catchments at different time scales. At the annual water balance level, runoff ratio values are found to be high across the country. At the event scale, the amount of rainfall in a given event represents a substantial amount of the total annual rainfall. Moreover, unit peak flow [maximum daily discharge] decreases with the catchment area and is not correlated with the rainfall depth of an event. Event runoff ratio is high; in fact it is much higher than values recorded in the EM and is the range of the NWM catchments. The third part concludes with a new clustering of the Lebanese catchments according to their physical and hydrological characteristics. The variables defined from the data analysis were used for the classification. Three classifications were carried out using catchments physical descriptors and runoff signatures separately. Catchments holding simultaneously the same physical and hydrological similarities were grouped together forming five “physically and hydrologically similar” catchments’ classes. Finally, a simple modeling approach at a monthly time step was tested using GR2M model. Different regionalization approaches were also compared. The discussion focuses on the analysis of the hydrological functioning of each basin and each class of basins.

Investment cost analysis in small hydropower plants in terms of efficiency and a case study in the Euphrates and Tigris basins

Article

Full-text available

Oct 2024

Ibrahim Yuksel

Flow rate is the basic parameter for calculating the energy capacity and investment costs of small hydropower plants. Because energy costs are directly related to energy capacity. While the energy capacity increases, the investment cost of the hydropower plant increases also. However, if the energy capacity is high, the energy production will be high and the investment cost will be amortized in a short time. In this study, small rivers in the Euphrates and Tigris Basins with previously determined hydropower capacities were selected, and the investment costs of small hydroelectric power plants to be designed on these rivers were analysed. For this analysis, 10 streams were selected from the Euphrates and Tigris Basins, and only Baskoy and Celebiyan streams have flow observation stations. The flow values of the remaining 8 streams were found by regression analysis using the basin and flow values of Baskoy and Celebiyan streams. Therefore, cost–benefit analyses were carried out separately for these flows in this study. In this study, because it includes the most effective hydrological parameters as well as many technical and economical parameters, the SMART Mini Hydro Tool Program was used.

Frequency curves of high and low flows in intermittent river basins for hydrological analysis and hydraulic design

Article

Full-text available

May 2024
STOCH ENV RES RISK A

Upper and lower percentiles of Flow Duration Curves (FDCs) of daily streamflow data were investigated to develop frequency curves. Upper percentiles with exceedance probability of 1, 5 and 10% (Q1, Q5, Q10) were used for high flows, and lower percentiles with non-exceedance probability of 10, 5 and 1% (Q90, Q95, Q99) for low flows. Median value (Q50) was covered to represent the average conditions of streamflow. A mixed frequency analysis based on the total probability theorem taking zero values into account was applied for the lower percentiles of FDC. Case studies were performed for three intermittent Streamflow Gauging Stations (SGSs) from Kucuk Menderes River Basin in western Turkey. An overall assessment of results shows that the best-fit probability distribution function does not change from one SGS to another considerably for low flows while each SGS has its own probability distribution function for high flows. Upper and lower percentiles, and median value were calculated at various return periods by using the identified probability distribution functions. The calculated values were plotted in the form of frequency curves of high flow percentiles and low flow percentiles. The frequency curves have a practically significant potential use in hydrological analysis, water resources management and hydraulic design under high and low flow conditions. They are yet open to further development for regionalization and their applicability can be extended to ungauged sites in river basins.

Regionalization methods in ungauged catchments for flow prediction: review and its recent developments

Article

Full-text available

Jun 2022

This review paper focuses on reporting and discussing the use of various regionalization methods (models) in hydrological prediction (runoff) in ungauged catchments (including arid and semi-arid region) with its recent developments. As a result, in light of recent developments, the concept of regionalization with its various models in terms of traditional (spatial proximity; arithmetic mean; physical similarity; and regression method) and emerging (hydrologic similarity; runoff response similarity; output averaging; flow duration curve method; soft and short stream flow measurement; and crowd-sourced water level data) techniques is reported. In such models, different calibration processes and their limitations with their uncertainties are also discussed. Validation methods and studies on reducing uncertainty are thus discussed to identify the suitable methodology (to get higher accuracy) for predicting the hydrological results. Thus, it is observed from this review that the emerging method significantly improves prediction accuracy across countries or regions and climate conditions (including arid and semi-arid regions).

Daily flow duration curve model for ungauged intermittent subbasins of gauged rivers

Article

Nov 2021
J HYDROL

In this study, we develop a daily flow duration curve model for ungauged intermittent subbasins of gauged rivers. The long-term mean streamflow of the river basin, one of the central parts in the model, is calculated with a regression model of annual precipitation and physical characteristics of the river basin; i.e., drainage area, basin relief, topographical slope, drainage density. The input data of the model are normally accesible, and this makes the model applicable to ungauged points within the river basin. Another central part of the model is the cease-to-flow point which makes the model significant for intermittent rivers. The daily streamflow discharge recorded in gauging stations over the river basin is nondimensionalized by dividing each with their own long-term mean, and their collection is transformed to fit the normal probability distribution; e.g., the normalized nondimensional daily streamflow data are used in the model. The streamflow data are inverted back to the original distribution for any given exceedance percentage by incorporating the cease-to-flow point, and are dimensionalized finally by using the empirically-derived long-term mean streamflow discharge. The model is applied on hundreds of thousands station-day daily streamflow data from three river basins in different geographical regions in Turkey. Results of the case studies are found quite promising and encouraging to propose the model as a good foundation for the daily flow duration curve at an ungauged intermittent subbasin of gauged rivers: However, it is noticebale that the model might have low performance in some particular gauging stations where the hydrological behavior deviates from the general characteristics of the river basin. This can be overcome by developing empirical models to approach better the observed long-term mean streamflow, which is a key issue of the model.

Debi-Sürek Eğrisi Yardımıyla Taban Akımının Hesaplaması: Samsun Kürtün Irmağı Örneği

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Apr 2021

AN ASSESSMENT OF THE INFLUENCE OF WATER ALLOCATION ON SUSTAINABLE WATER RESOURCES MANAGEMENT: A CASE STUDY OF THE NYANDO RIVER BASIN, KENYA

Thesis

Full-text available

Apr 2021

Ronald Sungu

PhD Thesis - Andrea Betterle

Thesis

Full-text available

Oct 2018

Andrea Betterle

This thesis focuses on the spatial correlation of river ﬂows, namely the correlation between daily streamﬂow timeseries at two generic locations along a river network. The correlation between river ﬂows is found to be a powerful indicator that quantiﬁes the similarity between a range of features characterizing the hydrological response of two catchments. As a statistical index, correlation can be considered as a metric quantifying the synchronicity of two signals. However, we ﬁnd that average seasonal ﬂows, streamﬂow variability, as well as other features deﬁning the hydrological response of catchments, are extremely similar at sites displaying highly correlated ﬂows. These evidences suggest a deep relationship between the physical processes that control the spatial correlation of river ﬂows and those responsible for the hydrological response of the landscape. A physically-based stochastic model was developed to quantify the correlation between daily ﬂows at two river sites. The model is based on a simple description of main catchment-scale hydrological processes and it requires basic hydroclimatic inputs. Despite its parsimony, the model succeeds in reproducing observed streamﬂow correlations in absence of discharge data, without requiring calibrations. Model predictions of streamﬂow correlation are useful in cases of limited hydrological information to export streamﬂow timeseries and other ﬂow statistics from gauged to ungauged locations. Especially where direct ﬂow measurements are not available, the model can be used to identify hydrologically similar locations, providing a means to spatially extend point information on ﬂow regimes. The model was employed to assess how the different physical processes underlying ﬂow dynamics ultimately affect streamﬂow correlation. The approach enables a proper quantiﬁcation of the effect due to intercatchment heterogeneities of runoff-driving processes on the ensuing hydrological similarity of two river basins. Spatial correlation is primarily controlled by the frequency and the intensity of rainfall events that simultaneously generate runoff in both catchments. The larger the number of rainfall events that simultaneously generate runoff in both catchments compared to the total set of runoff-generating events, the more similar will be the hydrological response of the two sites. Moreover, when simultaneous effective rainfall events have similar intensities, streamﬂow correlation will further increases. Interestingly, inter-catchment differences in response rates – namely how quickly a catchment drains after a rainfall event – mildly affect the correlation between daily ﬂows. The work presented in this thesis offers a new interpretation on how spatially heterogeneous geomorphoclimatic drivers of the water cycles ultimately affect seasonal patterns of ﬂow regimes along river networks. In an era of unsustainable anthropogenic pressures on the environment, the novel insights provided by this study offer new perspectives to understand and better manage hydrologic systems and river networks.

Surface water availability in ungauged catchments of Sub-Saharan Africa: A case study from Luwombwa sub-catchment, Zambia Surface water availability in ungauged catchments of Sub-Saharan Africa: A case study from Luwombwa sub-catchment, Zambia

Article

Full-text available

Jan 2025

Improving streamflow prediction reliability under limited hydrological observations is important for achieving sustainable water resources management of a river catchment. Inadequate baseline information about a catchment hydrological characteristic has hindered efficient water availability analysis and planning for water use, demand, and allocation among competing water users. The United Nations is globally implementing Sustainable Development Goals such as No. 6 (SDG-6) with emphasis on the need of having access to clean water and sanitation for all by 2030 which highly depend on water resources availability. The purpose of this study was to analyse and predict water availability in the Luwombwa sub-catchment through the application of the Soil and Water Assessment Tool (SWAT) based on its capability to simulate a wide range of hydrological processes of the sub-catchment of 7,363 km 2 considering past, present, and future climate scenarios. The results of the model performance achieved Nash-Sutcliffe Efficiency (NSE) of 0.74, a coefficient of determination (R 2) of 0.77 and a Percent Bias (PBIAS) of 3.84 during the model calibration period (2017-2022). During model validation period (2009-2015), performance evaluations achieved were NSE of 0.66, R 2 of 0.67 and PBIAS of 5.67 at the catchment outlet. The model's estimated water balance components were precipitation of 1107.7 mm comparable to the observed 1100.6 mm long-term average annual precipitation within the region, 63% evapotranspiration and 18% runoff while the combined percolation and deep recharge accounted for 19% of the annual precipitation. The results indicated the reliability of the model to predict catchment surface water availability, which provides baseline information for sustainable water resources management such as development of catchment management plans, water budget, and allocation. Therefore, the scientific insights from this study are capable of informing and enhancing the implementation process of the SDG-6 globally especially in Sub-Saharan regions. ARTICLE HISTORY

Surface water availability in ungauged catchments of Sub-Saharan Africa: A case study from Luwombwa sub-catchment, Zambia

Article

Full-text available

Dec 2025

Improving streamflow prediction reliability under limited hydrological observations is important for achieving sustainable water resources management of a river catchment. Inadequate baseline information about a catchment hydrological characteristic has hindered efficient water availability analysis and planning for water use, demand, and allocation among competing water users. The United Nations is globally implementing Sustainable Development Goals such as No. 6 (SDG-6) with emphasis on the need of having access to clean water and sanitation for all by 2030 which highly depend on water resources availability. The purpose of this study was to analyse and predict water availability in the Luwombwa sub-catchment through the application of the Soil and Water Assessment Tool (SWAT) based on its capability to simulate a wide range of hydrological processes of the sub-catchment of 7,363 km2 considering past, present, and future climate scenarios. The results of the model performance achieved Nash-Sutcliffe Efficiency (NSE) of 0.74, a coefficient of determination (R2) of 0.77 and a Percent Bias (PBIAS) of 3.84 during the model calibration period (2017–2022). During model validation period (2009–2015), performance evaluations achieved were NSE of 0.66, R2 of 0.67 and PBIAS of 5.67 at the catchment outlet. The model’s estimated water balance components were precipitation of 1107.7 mm comparable to the observed 1100.6 mm long-term average annual precipitation within the region, 63% evapotranspiration and 18% runoff while the combined percolation and deep recharge accounted for 19% of the annual precipitation. The results indicated the reliability of the model to predict catchment surface water availability, which provides baseline information for sustainable water resources management such as development of catchment management plans, water budget, and allocation. Therefore, the scientific insights from this study are capable of informing and enhancing the implementation process of the SDG-6 globally especially in Sub-Saharan regions. Key Words: Ungauged catchment, hydrological modelling, water availability, evaporation, surface runoff

A machine learning algorithm for predicting naturalized flow duration curves at human influenced sites and multiple catchment scales

Preprint

Full-text available

Sep 2024

Regional flow duration curves (FDCs) often reflect streamflow influenced by human activities. We propose a new machine learning algorithm to predict naturalized FDCs at human influenced sites and multiple catchment scales. Separate Meta models are developed to predict probable flow at discrete exceedance probabilities across catchments spanning multiple stream orders. Discrete exceedance flows reflect the stacking of k-fold cross-validated predictions from trained base ensemble machine learning models with and without hyperparameter tuning. The quality of individual base models reflects random stratified shuffling of spilt catchment records for training and testing. A Meta model is formed by retraining minimum variance base models that are bias corrected and used to predict final flows at selected percentiles that quantify uncertainty. Separate Meta models are developed and used to predict naturalised stochastic flows at other discrete exceedance probabilities along the duration curve. Efficacy of the new method is demonstrated for predicting naturalized stochastic FDCs at human influenced gauged catchments and ungauged stream reaches of unknown influences across Otago New Zealand. Important findings are twofold. First, independent observations of naturalised Median flows compare within few percent of the 50th percentile predictions from the FDC models. Second, the naturalised Meta models predict FDCs that outperform the calibrated SWAT model FDCs at gauge sites in the Taieri Freshwater Management Unit: Taieri at Tiroiti, Taieri at Sutton Creek, and Taieri River at Outram. Departures in the naturalised reference state are interpreted as flow regime changes across the duration curves. We believe these Meta models will be useful in predicting naturalised catchment FDCs across other New Zealand regions using physical catchment features available from the national data base.

Assessment of small hydropower potential and development of flow irrigation scheme in an ungauged stream: A case study from Kaliyani River in Assam, India

Article

Full-text available

Sep 2021

Potential Legacy of SWOT Mission for the Estimation of Flow–Duration Curves

Article

Full-text available

Jul 2024

Flow–duration curves (FDCs) provide a compact view of the historical variability of river flows, reflecting climate conditions and the main hydrologic features of river basins. The Surface Water and Ocean Topography (SWOT) satellite mission will enable the estimation of river flows globally, by sensing rivers wider than 100 m with a sampling recurrence from 3 to 21 days. This study investigated the lifetime mission potential for FDC estimation through the comparison between remotely-sensed and empirical FDCs. We employed the Global Runoff Data Center dataset and derived SWOT-like river flows by selecting gauging stations of rivers wider than 100 m with more than 10-year long daily river flow time series. Overall, 1200 gauged river cross-sections were examined. For each site, we created a set of 24 SWOT-simulated FDCs (i.e., based on different sampling recurrences, mean biases, and random errors) to be compared against their empirical counterparts through the Nash–Sutcliffe efficiency and the mean relative error. Our results show that climate and the sampling recurrence play a key role on the performance of SWOT-based FDCs. Tropical and temperate climates performed the best, whereas arid climates mostly revealed higher uncertainties, especially for high- and low-flows.

Urban flash floods modeling in Mzuzu City, Malawi based on Sentinel and MODIS data

Article

Full-text available

May 2024

Floods are major hazard in Mzuzu City, Malawi. This study applied geospatial and hydrological modeling techniques to map flood incidences and hazard in the city. Multi-sensor [Sentinel 1, Sentinel 2, and Moderate Resolution Imaging Spectroradiometer (MODIS)] Normalized Difference Vegetation Index (NDVI) datasets were used to determine the spatio-temporal variation of flood inundation. Ground control points collected using a participatory GIS mapping approach were used to validate the identified flood hazard areas. A Binary Logistic Regression (BLR) model was used to determine and predict the spatial variation of flood hazard as a function of selected environmental factors. The Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) was used to quantify the peak flow and runoff contribution needed for flood in the city. The runoff and peak flow from the HEC-HMS model were subjected to extreme value frequency analysis using the Gumbel Distribution approach before input into the Hydrologic Engineering Center River Analysis System (RAS) (HEC-RAS). The HEC-RAS model was then applied to map flood inundated areas producing flood extents maps for 100, 50, 20, and 10-year return periods, with rain-gauge and Climate Prediction Center MORPHed precipitation (CMORPH) satellite-based rainfall inputs. Results revealed that selected MODIS and Sentinel datasets were effective in delineating the spatial distribution of flood events. Distance from the river network and urban drainage are the most significant factors ( p < 0.05) influencing flooding. Consequently, a relatively higher flood hazard probability and/susceptibility was noted in the south-eastern and western-most regions of the study area. The HEC-HMS model calibration (validation) showed satisfactory performance metrics of 0.7 (0.6) and similarly, the HEC-RAS model significantly performed satisfactorily as well ( p < 0.05). We conclude that bias corrected satellite rainfall estimates and hydrological modeling tools can be used for flood inundation simulation especially in areas with scarce or poorly designed rain gauges such as Mzuzu City as well as those affected by climate change. These findings have important implications in informing and/updating designs of flood early warning systems and impacts mitigation plans and strategies in developing cities such as Mzuzu.

Learning from experience: A survey of existing micro-hydropower projects in Ba'Kelalan, Malaysia

Article

Full-text available

May 2013

Rural electrification to help rural communities improve their quality of life needs to be designed in a sustainable manner with the intention of keeping village culture and environment from eroding. Micro-hydropower systems (MHS), especially run-of river schemes, are examples of renewable energy projects that, if managed well, can be socially and environmentally sustainable. This paper presents the results of a field survey conducted in Ba'Kelalan, in Sarawak, Malaysia, where several MHS have been implemented by various funding agencies using different planning mechanisms as well as different design and operational procedures. Quantitative and qualitative analyses were used in a case study comparison of two MHS in Ba'Kelalan based on criteria such as system loads, electricity tariff, the level of community involvement in the project, and the arrangements put in place for maintenance. Several barriers to sustainability were found in the operation and maintenance of the MHS due to a lack of knowledge by unskilled operators. The key lessons learnt from the case study are that sustainable development of MHS requires financial and load distribution management at the beginning of the project, as well as capacity building for both operation and maintenance personnel, as well as the community.

A geostatistical approach to estimate flow duration curve parameters in ungauged basins

Article

Full-text available

Aug 2023

Flow duration curve represents the percentage of time that a river flow is equal to or greater. As these curves provide a direct response to the behavior of water resources in a basin, which is used widely in hydropower projects, it is important to predict flow duration curves in no metering basins, named “ungagged basins.” The geostatistical approach to predict the values of these curves in non-measured stations shows the expansion of the range of studies in this topic. The aim of this study is to predict the flow duration curve over long periods of time in a basin with ungauged regions using probability kriging, inverse distance weighting (IDW) and maximum likelihood (ML) methods. Flow data from 38 flow measuring stations in the Dez Basin were used to map different discharges of the flow duration curve, and as a result, in order to complete their values, zone and quantify them, three different values of Q 10 , Q 50 and Q 90 of the flow duration curve acquired. The results show that as the flow rate increases (or the time percentage decreases), the amount of computational error increases and in all cases, the probability kriging method has a smaller error (0.96) than the IDW (1.65) and ML (1.15) methods.

Characteristics and Controlling Factors of the Drought Runoff Coefficient

Article

Full-text available

Apr 2021

Rei Itsukushima

Increasing water demand due to population growth, economic development, and changes in rainfall patterns due to climate change are likely to alter the duration and magnitude of droughts. Understanding the relationship between low-flow conditions and controlling factors relative to the magnitude of a drought is important for establishing sustainable water resource management based on changes in future drought risk. This study demonstrates the relationship between low-flow and controlling factors under different severities of drought. I calculated the drought runoff coefficient for six types of occurrence probability, using past observation data of annual total discharge and precipitation in the Japanese archipelago, where multiple climate zones exist. Furthermore, I investigated the pattern of change in the drought runoff coefficient in accordance with the probability of occurrence of drought, and relationships among the coefficient and geological, land use, and topographical factors. The drought runoff coefficient for multiple drought magnitudes exhibited three behaviors, corresponding to the pattern of precipitation. Results from a generalized linear model (GLM) revealed that the controlling factors differed depending on the magnitude of the drought. During high-frequency droughts, the drought runoff coefficient was influenced by geological and vegetation factors, whereas land use and topographical factors influenced the drought runoff coefficient during low-frequency droughts. These differences were caused by differences in runoff, which dominated stream discharge, depending on the magnitude of the drought. Therefore, for effective water resource management, estimation of the volume of drought runoff needs to consider the pattern of precipitation, geology, land use, and topography.

Patterns of Recent Changes in Channel Morphology and Flows in the Upper and Middle Odra River

Article

Full-text available

Jan 2023

Our research introduces the river regulation effects on three sections of the upper and middle Odra River (south-western Poland), with differently channelized parts. In the upper and lower reaches, the river was straightened, narrowed, and trained with groins, whereas in the middle section, it was also impounded by numerous barrages. The discharge duration (DD) and water stage duration (WSD) curves for water-gauge stations from these river sections were analyzed to recognize changes in river flows and channel morphology since the mid-20th century. This analysis is supplemented by an examination of repeated surveys of the gauge cross sections of the river, annual precipitation totals in its catchment, and their relationship to the variation of the North Atlantic Oscillation (NAO) index. Our findings provide new hydrological insights for the region. The three river sections exhibited different patterns of the adjustment of the channel morphology to the river channelization: upper section was typified by channel incision, middle section by channel stability, and lower section by channel incision in its upper part and vertical stability of the channel bed in the lower part. Barrages in the middle section stabilized water stages in a wide range of hydrological conditions. Annual precipitation totals and river runoff did not change systematically over the study period. The variation in precipitation totals was inversely related to annual values of the NAO index. The study confirms the usefulness of DD/WSD curves to analyze changes in river runoff and the vertical position of the channel bed.

Quantifying Intra-Catchment Streamflow Processes and Response to Climate Change within a Climatic Transitional Zone: A Case Study of Buffalo Catchment, Eastern Cape, South Africa

Article

Full-text available

Aug 2022

The complexity of streamflow processes inhibits significant information about catchment performance and its sensitivity to climate change. Little is known about the severity of climate change within the coastal area of the monsoon–subtropical zone of climatic transition. This study advances a quasi-local scale analysis to simplify daily streamflow dynamics and their relationship with monthly hydro-climatic series (1981–2020) using six gauging stations on the Buffalo River due to its socio-economic significance. An integrated framework based on continuous wavelet transform (CWT), wavelet coherence (WC), innovative trend analysis (ITA), Mann–Kendall (MK), Sequential Mann–Kendall, and Pettitt tests were employed. CWT showed huge declivity in daily streamflow intensity (7676 to 719), >100 mm/day streamflow frequency (15 to 0), and wetness spell time-gap. WC obtained significant streamflow–rainfall co-movement of 8–196-month periodicities, which characterized Buffalo as anti-phase (1–4-month), lag-lead (8–32-month), and in-phase (64–196-month) in processes. The Buffalo River’s sensitivity to significantly decreasing rainfall trends and increasing temperature trends depicts Streamflow–ENSO teleconnection. Contrarily, ITA and MK exhibited significantly increasing trends of tributaries’ low flow and inferred the perennial status of the catchment. The Pettitt test corroborates the deductions and asserts 1990 (temperature), 1996 (streamflow), and 2004/2013 (rainfall) as the abrupt change points, while SMK captured a critical streamflow slump in 2015–2020. Overall, the study proved the reductionist approach and model framework to achieve the hydrological process simplification and resolution of hotspots of hydrologic extremes within a bimodal climate with complex topography. This study remarks on the management policy of the BR and provides a reference for managing water resources and catchment hydro-climatic extremes.

Spatial distribution of groundwater recharge, based on regionalised soil moisture models in Wadi Natuf karst aquifers, Palestine

Article

Full-text available

Feb 2022
HESS

While groundwater recharge is considered fundamental to hydrogeological insights and basin management and studies on its temporal variability are in great number, much less attention has been paid to its spatial distribution, by comparison. And in ungauged catchments it has rarely been quantified, especially on the catchment scale. For the first time, this study attempts such analysis, in a previously ungauged basin. Our work is based on the results of field data (as published in Messerschmid et al., 2020) of several soil moisture stations, which represent five geological formations of karst rock in Wadi Natuf, a semi-arid to sub-humid Mediterranean catchment in the occupied Palestinian West Bank. For that purpose, recharge was conceptualised as deep percolation from soil moisture under saturation excess conditions, which had been modelled parsimoniously and separately with different formation-specific recharge rates. For the regionalisation, inductive methods of empirical field measurements and observations were combined with deductive approaches of extrapolation, based on a new basin classification framework (BCF) for Wadi Natuf, thus following the recommendations for hydrological Prediction in Ungauged Basins (PUB), by the International Association of Hydrological Sciences (IAHS). Our results show an average annual recharge estimation in Wadi Natuf catchment (103 km2), ranging from 235 to 274 mm (24 to 28×106 m3) per year, equivalent to recharge coefficients (RCs) of 39 %–46 % of average annual precipitation (over a 7-year observation period but representative of long-term conditions as well). Formation-specific RC values, derived from empirical parsimonious soil moisture models, were regionalised and their spatial distribution was assessed and quantified on the catchment scale. Thus, for the first time, a fully distributed recharge model in a hitherto entirely ungauged (and karstic) aquifer basin was created that drew on empirical methods and direct approaches. This was done by a novel combination of existing methods and by creating a unified conceptual basin classification framework for different sets of physical basin features. This new regionalisation method is also applicable in many comparable sedimentary basins in the Mediterranean and worldwide.

A multi-scale study of the dominant catchment characteristics impacting low-flow metrics

Article

Full-text available

Dec 2021
HYDROL PROCESS

Low flows can impact water use and instream ecology. Therefore, reliable predictions of low-flow metrics are crucial. In this study, we assess which catchment characteristics (climate, topography, geology and landcover) can explain the spatial variability of low-flow metrics at two different scales: the regional scale and small headwater catchment scale. For the regional-scale analysis, we calculated the mean 7-day annual minimum flow (qmin), the mean of the flow that is exceeded 95% of the year (q95), and the hydrograph recession coefficient (C) for 280 independent gauging stations across the Swiss Plateau and the Swiss Alps for the 2000 to 2018 period. We assessed the relation between 44 catchment characteristics and these three low-flow metrics based on correlation analysis and a random forest model. Low-flow magnitudes across the Swiss Plateau were positively correlated with the fraction of the area covered by sandstone bedrock or alluvium, and with the area that has a slope between 10° and 30°. Across the Swiss Alps, low-flow magnitudes were positively correlated with the fraction of area with slopes between 30° and 60°, and the area with glacial deposits and debris cover. There was good agreement between observations and predictions by the random forest regression model with the top 11 catchment characteristics for both regions: for 80% of the Swiss Plateau catchments and 60% of the Swiss Alps catchments, we could predict the three low-flow metrics within an error of 30%. The residuals of the regression model, however, varied across short distances, suggesting that local catchment characteristics affect the variability of low-flow metrics. For the local-scale headwater catchments, we conducted one-day snapshot field campaigns in 16 catchments during low-flow periods in 2015 and 2016. The measurements in these sub-catchments also showed that areas with sandstone bedrock and a good storage-to-river connectivity had above average low-flow magnitudes. Including knowledge on local catchment characteristics may help to improve regional low-flow predictions, however, not all local catchment characteristics were useful descriptors at larger scales.

Streamflow estimation at partially gaged sites using multiple-dependence conditions via vine copulas

Article

Full-text available

Aug 2021
HESS

Kuk-Hyun Ahn

Reliable estimates of missing streamflow values are relevant for water resource planning and management. This study proposes a multiple-dependence condition model via vine copulas for the purpose of estimating streamflow at partially gaged sites. The proposed model is attractive in modeling the high-dimensional joint distribution by building a hierarchy of conditional bivariate copulas when provided a complex streamflow gage network. The usefulness of the proposed model is firstly highlighted using a synthetic streamflow scenario. In this analysis, the bivariate copula model and a variant of the vine copulas are also employed to show the ability of the multiple-dependence structure adopted in the proposed model. Furthermore, the evaluations are extended to a case study of 54 gages located within the Yadkin–Pee Dee River basin in the eastern USA. Both results inform that the proposed model is better suited for infilling missing values. To be specific, the proposed multiple-dependence model shows the improvement of 9.2 % on average compared to the bivariate model from the historical case study. The performance of the vine copula is further compared with six other infilling approaches to confirm its applicability. Results demonstrate that the proposed model produces more reliable streamflow estimates than the other approaches. In particular, when applied to partially gaged sites with sufficient available data, the proposed model clearly outperforms the other models. Even though the model is illustrated by a specific case, it can be extended to other regions with diverse hydro-climatological variables for the objective of infilling.

Environmental Water Requirements in Mountainous Areas

Chapter

Oct 2021

Mountainous areas and river systems

Chapter

Jan 2021

Nikolaos Skoulikidis

Mountains and mountain rivers provide a multitude of invaluable goods and services to a profound portion of the planet’s population. As “water towers” of the Earth mountains are sources of the mightiest world rivers and play a pivotal role for global biodiversity, freshwater, and sediment supply. Distinct morphological, climatic, hydrological, hydrochemical, and biological features of mountainous river ecosystems, compared to lowland ones, make them particularly fragile and vulnerable to human interference. Despite a number of remote mountain areas and rivers still remaining intact from direct human pressures, the majority of mountain ecosystems, are being increasingly threatened by adverse local and global changes driven by market economy. To efficiently conserve and sustainably use mountain ecosystems and contribute to the survival of the planet, it is critical to change our standards and life attitudes by realizing and appreciating our immediate connection to the global ecosystem, change attitudes and current consumption patterns, and stimulate the ways our global society functions and interacts with the natural environment.

Quantification of environmental water requirements; how far can we go?

Chapter

Oct 2021

The modification of sediment and flow regimes caused by damming and river regulation has deleterious effects on the ecological and morphological river processes. This alteration of river systems triggered the implementation of safeguarding environmental flows (e-flows) defined as “the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and wellbeing that depend on these ecosystems”. In the last decades, physical habitat simulation approaches emerged as fundamental stand-alone or supplementary methods for e-flow assessment. These approaches combine three main components: (1) hydraulic simulation, (2) habitat suitability modeling, to determine the quality of the available habitat, and (3) hydrological analyses (under current and climate change scenarios). E-flow regimes are finally defined, by assessing the spatial and temporal habitat variability for the target taxa or community, after combining these three components. During the process of physical habitat simulation some river processes, such as sediment transport and morphological changes, are often neglected while uncertainties arise from every component. We reviewed the elements that should be considered in every component of the physical habitat simulation to reduce uncertainties with emphasis on the actual trends on the topic and how sediment transport and river morphodynamics can be included within this methodological framework.

Hydrological data sources and analysis for the determination of environmental water requirements in mountainous areas

Chapter

Jan 2021

Konstantinos X. Soulis

In all available methodologies for the assessment of the environmental flow requirements, a sufficient knowledge of the natural hydrological regime is essential. In this chapter the hydrological data that are required in environmental flow assessment studies, their main characteristics, and their importance as well as the specific challenges in the case of mountainous areas are analyzed. The various available data sources, the measurement and processing of hydrological data, and the utilization of modeling techniques for the estimation of streamflow data in the case of ungauged or poorly gauged watersheds and for the naturalization of streamflow data are also presented. A short description of hydrological data series analysis for the determination of environmental water requirements is provided as well. Finally, sources for further reading are provided in each section.

Characterization of Irreversible Land Subsidence in the Yazd‐Ardakan Plain, Iran From 2003 to 2020 InSAR Time Series

Article

Full-text available

Nov 2021

Groundwater extraction rates exceeding recharge are occurring throughout Iran to sustain industrial and agricultural activities, resulting in land deformation in many areas, particularly in the Yazd‐Ardakan Plain (YAP) in central Iran's dry and desert regions. In this study, Interferometric Synthetic Aperture Radar (InSAR) time series analysis and statistical models are applied to characterize the controls on land subsidence in the YAP from 2003 to 2020. Our results reveal the existence of a northwest‐southeast elongated area of 234.45 km² experiencing subsidence at rates up to 15 cm/yr. In the YAP, the international Airport, railway, transit road, and several industrial and historical sites are threatened by the differential subsidence. Well data confirm that groundwater levels have decreased by 18 meters between 1974 and 2018, driving the compaction of sediments within the underlying aquifer system. Our statistical analysis shows that the thickness of a shallow, clay‐rich aquitard layer controls the extent of the observed subsidence and the Independent Component Analysis of the InSAR time series shows that inelastic compaction is dominated. This work reveals that current groundwater extraction practices in central Iran are not sustainable and result in permanent subsidence, ground fractures with impact on infrastructures, and a permanent decrease in water storage capacity.

The Long‐Term Response of Alternate Bars to the Hydrological Regime

Article

Full-text available

Jul 2021
WATER RESOUR RES

Migrating bars are large‐scale, alternate bedforms that often develop in channelized river reaches, as a consequence of an intrinsic instability of the erodible channel bed. Their behavior under steady flow conditions has been widely investigated by means of theoretical, experimental, and numerical models, which revealed that bar formation occurs when the width‐to‐depth ratio of the channel exceeds a critical threshold value. Conversely, no much information is available about the long‐term, average characteristics of alternate bars in the case of a complex flow regime, which makes the width‐to‐depth ratio highly variable in time. Starting from the state‐of‐the‐art theoretical models of bar dynamics, we propose a novel methodology to determine the long‐term bar response to the hydrological river regime and the associated “bar‐forming” discharge that, if applied steadily, would produce the same morphological response. We derive a generalized criterion to define whether bars are expected to form and to estimate the long‐term bar topography, depending on flow probability density function and channel characteristics (width, slope and sediment size). Our procedure differs from the classical methods to define formative discharge, inasmuch as it accounts for the specific and reversible response of bar topography to the different flow stages that compose the hydrological regime. Application to four different gravel bed reaches in the Alpine region shows the capability of the procedure to interpret remarkably different riverbed morphologies and to provide a reasonable prediction of the observed bar height, thus suggesting its potential to analyze long‐term morphological trajectories following hydrological alterations and river restoration projects.

Effects of source digital elevation models in assessment of gross run- off-river hydropower potential: A case study of West Rapti Basin, Nepal

Article

Full-text available

Apr 2021

Advancements in Geographical Information System (GIS), Remote Sensing (RS) technology, hydrologic modeling and availability of wider coverage hydrometeorological data have facilitated the use of GIS and hydrological modelling tools in studies related to hydropower potential. Digital Elevation Model (DEM) is the primary data required for these tools. They have become more accessible and many are freely available. These DEMs have different resolution and their errors vary due to their primary data acquisition techniques and processing methods. However, their effects on the hydropower potential assessment are less investigated. This study evaluates the effects of 6 freely available DEMs: ALOS 12.5 m, SRTM 90 m, SRTM 30 m, ASTER G-DEM version-3 30 m, AW3D 30 m and Cartosat-1 version-3 30 m on the Gross Run-off-River Hydropower Potential (GRHP) assessment, using GIS and hydrological modelling tools. West Rapti River (WRR) basin in Nepal was chosen for the case study. Soil and Water Tool (SWAT) hydrological model, coupled with GIS was used to discretize the WRR basin into several sub-basins/streams. Flow at the inlet and outlet of streams were estimated from the SWAT model whereas the topographic head was extracted from the DEMs. The GRHP of the streams were computed using the estimated stream flow and the topographic head for flows at 40% to 60% Probability of Exceedance (PoE). The total potential of the basin was computed by summing up the potential of all streams. The GRHP of WRR basin for flows at 40% PoE was estimated as 512 MW for ALOS 12.5 m resolution DEM, referred as a base case in this study. The GRHP estimated from the remaining DEMs showed the variation of less than 6% compared to the base case. The topographic head was found to be sensitive with respect to the DEM resolution and the highest variations were observed in the main river channels.

Official Journal of Nepal Engineers' Association (NEA) ENGINEERING ISSUES AND SOLUTIONS (formerly known as Nepal Engineers Associations' Technical Journal)

Article

Full-text available

Apr 2021

Physical Continuous-Time Swat+ Modeling Approach to Develop Flow Duration Curves within the Contiguous United States

Preprint

Jan 2025

Flow duration curve prediction: A framework integrating regionalization and copula model

Article

Nov 2024
J HYDROL

Forest Hydrology in High Tropical Mountains: Contrasting EcoHydrological Processes in Temperate Broadleaved and Sub-Alpine-Conifer-Mixed Tropical Montane Forests of Eastern Himalaya, India

Preprint

Full-text available

Jul 2024

Ecohydrological processes controlling key water and carbon services remain least understood in the high tropical mountains, such as the Himalaya. In a first, the study compares the hydrological functioning of the world’s highest non-glaciated headwater catchments (<25 km2) in the Eastern Himalaya using a physically-based, data-driven mechanistic baseflow-separation filter developed by Furey and Gupta (2001), discharge variability and lag regression analysis. The five catchments cover gradients of elevation (3750–4900 mm), catchment size (0.2-13.4 km2), stream-order (first-to-third), precipitation (3700-4900 mm) dominated by temperate broad-leaved (henceforth temperate) and sub-alpine conifer-mixed (henceforth alpine) forests. We empirically derive coefficients of overland flow, evapotranspiration, and groundwater recharge using the filter, which performed better in temperate than in alpine streams. The overland and rapid sub-surface flow varied considerably with antecedent moisture, catchment properties (size, bed-slope, and geomorphology), and vegetation. The overland flow and groundwater recharge coefficients were significantly higher in temperate than in alpine streams. Hydrogeological and catchment characteristics dominated groundwater storage and recession rather than vegetation. Instead, vegetation and climate were primary factors governing evapotranspiration and overland flow across the streams, while catchment properties were critical secondary factors. Seasonally, the low flows were primarily governed by local hydrogeology, catchment size, and snowmelt, whereas vegetation characteristics modulated high flows. Vegetation and catchment properties controlled the diel and seasonal flows, respectively. Low-intensity precipitation (<10 mm hr-1) facilitated highest recharge in temperate and alpine catchments. Future precipitation intensification and snowfall decline will likely generate higher runoff in temperate and reduced baseflows in alpine catchments. The study fills a critical knowledge gap in improving the accuracy of regional land-surface-atmosphere interaction models by factoring in the contrasting responses of different ecosystems in the Himalaya, where changes in vegetation and precipitation patterns with a changing climate may significantly impact the ecosystem services and regional water security.

Evaluación de la respuesta hidrológica del modelo DWB en la curva de duración de caudales a nivel de cuenca y microcuenca, caso de estudio la cuenca del río Sogamoso, Colombia

Article

Apr 2024

Las curvas de duración de caudales (CDC) reflejan los efectos de las características de una cuenca sobre los caudales, esto sin tener en cuenta la temporalidad de ocurrencia. Tradicionalmente, se construyen a partir de registros históricos registrados por estaciones y son insumo para el cálculo de índices de gestión del recurso hídrico como el índice de regulación Hídrica (IRH). Debido a la escasez de registros hidrológicos, en la práctica se recurre a estrategias de regionalización de las CDC para estudiar aquellas cuencas no instrumentadas. Este trabajo busca evaluar el desempeño del modelo DWB a partir de entradas diarias en la simulación de CDC en dos subcuencas del río Sogamoso que tienen características diferentes (El Tablazo y Puente Colonial). Se desarrolla una metodología que usa el índice de aridez para identificar 4 periodos hidrológicamente contrastantes, 2 periodos húmedos y 2 periodos secos. Posteriormente, se implementaron 8 experimentos de calibración – validación a partir de la combinación de los periodos previamente identificados. Finalmente, a partir de la revisión cualitativa y cuantitativa con firmas de sesgo en los flujos medios, altos y bajos se evaluaron los resultados arrojados por el modelo DWB. En términos generales, se encontró que el ejercicio fue exitoso en la subcuenca de mayor tamaño (El Tablazo) y que el modelo no logra reproducir los caudales bajos, generando subestimaciones en todos los experimentos realizados.

Outcomes of synthesis

Chapter

Apr 2013

Predicting water runoff in ungauged water catchment areas is vital to practical applications such as the design of drainage infrastructure and flooding defences, runoff forecasting, and for catchment management tasks such as water allocation and climate impact analysis. This full colour book offers an impressive synthesis of decades of international research, forming a holistic approach to catchment hydrology and providing a one-stop resource for hydrologists in both developed and developing countries. Topics include data for runoff regionalisation, the prediction of runoff hydrographs, flow duration curves, flow paths and residence times, annual and seasonal runoff, and floods. Illustrated with many case studies and including a final chapter on recommendations for researchers and practitioners, this book is written by expert authors involved in the prestigious IAHS PUB initiative. It is a key resource for academic researchers and professionals in the fields of hydrology, hydrogeology, ecology, geography, soil science, and environmental and civil engineering.

Recommendations

Chapter

Apr 2013

PUB in practice: case studies

Chapter

Apr 2013

Application of Grasshopper Optimization Algorithm in Design Process of Lead Rubber Bearing Seismic Isolator

Conference Paper

Full-text available

May 2022

In this study, sensitivity analysis of the seismic behavior of the isolated building structures in relation to the mechanical parameters of the lead rubber bearing seismic isolation (LRB) system was evaluated. The nonlinear behavior of the LRB isolator was simulated by a bilinear hysteresis model. Also, the nonlinear time history dynamic analysis method was used to analyze the isolated structures. The design optimization problem of the LRB isolator was solved using the grasshopper optimization algorithm (GOA). The results of sensitivity analysis on the seismic behavior of isolated structures with LRB show that the parameter of base shear yield ratio is the most effective and the mass irregularity is the least effective parameter on the seismic behavior of isolated structures.

Weingartner, R., Blöschl, G., Hannah, D., Marks, D., Parajka, J., Pearson, C., . . . Viglione, A. (2013). Prediction of seasonal runoff in ungauged basins. In G. Blöschl, M. Sivapalan, T. Wagener, A. Viglione, & H. Savenije (Eds.), Runoff Prediction in Ungauged Basins: Synthesis across Processes, Places and Scales (pp. 102-134). Cambridge: Cambridge University Press. doi:10.1017/CBO9781139235761.009

Chapter

Apr 2013

C. P. Pearson

MÜHENDİSLİK ALANINDA ARAŞTIRMA VE DEĞERLENDİRMELER -II

Chapter

Full-text available

Dec 2021

INDICADORES DE DESEMPENHO ESTATÍSTICOS PARA RESERVATÓRIOS: UMA REVISÃO DE LITERATURA

Chapter

Full-text available

Jan 2021

The construction of the flow duration curve and the regionalization parameters analysis in the northwest of China

Article

Full-text available

May 2021

Daily runoff is the data to estimate the water resources in a river. In many catchments, the daily discharge is not well observed. Flow duration curve is an important characteristic of daily runoff, and important for the design of water conservancy projects. In the ungauged catchments, the evaluation of distribution functions and the parameters of flow duration curve is a helpful method to understand the characteristics of the flow. This study uses data from 19 hydrological stations to evaluate the applicability of 11 distribution functions to simulate flow duration curves in the northwest of China. The fitted flow duration curves are evaluated by Nash-Sutcliffe efficiency, the root mean square relative error and the coefficient of determination. The evaluation shows that, among the 11 distribution functions, the log normal model is the most suitable model to construct flow duration curves of 19 hydrological stations. Based on a multivariate linear regression model, a regional model of distribution parameters is constructed, including functions of watershed geomorphologic and climatic characteristics. The analysis of Baijiachuan hydrological station shows that the parameters a and b showed a decreasing trend. This study presents an innovative approach to evaluate regionalized parameters of flow duration curves considering the impacts of geomorphologic and climatic characteristics. HIGHLIGHTS Daily discharge at 19 hydrological stations in the northwest of China are used to evaluate the applicability of 11 distribution functions to simulate flow duration curves.; The log normal distribution function is the most suitable model to construct flow duration curves.; A regional model of distribution parameters is constructed, and they are functions of watershed geomorphologic and climatic characteristics.;

Toward geostatistical unbiased predictions of flow duration curves at ungauged basins

Article

Apr 2021
ADV WATER RESOUR

Flow duration curves (FDCs) represent the percentage of time (or duration) during which a given streamflow is equaled or exceeded. Flow duration curves provide a rapid and direct response to the behavior of water resources in a basin. Thus, predicting FDCs is important in basins with little or no monitoring for both all-time and seasonal periods. The geostatistical approach for predicting FDCs at ungauged sites represents an advancement in this research topic. However, poor results have been observed, particularly overestimates (positive bias) for high durations, i.e., low flows. This study aims to predict FDCs in all-time and seasonal periods by using a geostatistical approach based on models, toward unbiased prediction. Streamflow data from 81 stream gauges made available by the Brazilian National Water Agency (ANA) have been used. These stations have a high spatial density and are well spread across the study area. To map the FDCs, and consequently, all their quantiles, the scale and shape parameters of the FDCs were modeled geostatistically. First, some basic assumptions for the FDC parameters such as data normality and spatial stationarity were verified. After an inference by the maximum likelihood method was performed to fit the geostatistical models and estimate the best model forms, we compared them with the benchmark models (i.e. regression models). Finally, the spatial interpolation was performed and the performance was assessed by a leave-one-out cross-validation. The geostatistical models yielded better fits and performance for mapping the FDCs than the regression models. Both the median of relative residuals for all-time and seasonal periods were unbiased for the entire duration. We suggest that the fixed effect modeling of the geostatistical models, associated with external drifts, led to this better and unbiased performance.

Investigation of the optimal method for determining hydropower potential of small streams: a case study Batman Basin in Turkey

Article

Apr 2021

Global energy consumption has provoked a need to explore alternative energy sources including run-of-the-river hydropower projects. In Turkey, hydroelectric energy production by utilizing small rivers has not reached the desired level yet. The aim of this study is to provide that hydroelectric energy production can be increased at the desired level in the Batman sub-basin and will offer a simplified procedure to estimate the potential power generation that can be applied locally. In this study, geographic information system (GIS) was used for elevation and morphological features of the basins and, a hydrological model and instantaneous discharge used for flow discharges. In the hydrological model, the parameters of the proxy basins were calibrated and transferred to the sub-basins were used. As the river discharge data of ten sub-basins, results of a hydrological model and for streams without flow observation stations instantaneous discharge estimations based on velocity measurement were used made by floats and pitot tube methods. Then, gross hydroelectric potential (GHP), hypsographic curve (HC), and head-flow (HF) methods for ten sub-basins were calculated. Flow duration curve (FDC) was used for the hydroelectric feasibility analysis. The study revealed that the hydropower potential of a river basin can be correctly assessed by employing a digital elevation model, stream network data, and a hydrological model, such as the HEC model, within a GIS framework. Also, considering the hydroelectric potential results (51507 MWh), it means an important energy potential for the region as it will support rural development and contribute to the country’s economy.

Probabilistic Flow Duration Curves for Use in Environmental Planning and Management

Article

Full-text available

Jan 1997

When ,dealing with the planning and management,of water,uses in a river, the knowledge of the probabilistic structure of minima of daily or of multiple-day flows is often required. As a tool for straightforward determination of different levels of flow minima, flow duration curves (FDCs) are particularly suited for planning purposes. In this paper, FDCs referred to annual samples are interpolated with lognormal,curves and their probabilistic structure is obtained through the statistical analysis of the two lognormal,parameters. Distribution of these parameters is shown to be normal, so that the discharge with a given duration related to a return period T can be easily evaluated. To build FDCs in ungauged basins, relations between the moments of the parameters and catchment characteristics have been investigated, with reference to the data available in the Basilicata region (Italy). For both parameters, most of the variance of the first moment can be explained by the Base Flow Index (BFI), which,can be estimated ,from ,geology. The second ,moment ,can be derived considering that the coefficient of variation is constant over the whole region. Since the curves are considered in dimensionless form, estimation of the mean annual runoff is finally needed to obtain the dimensional probabilistic FDCs in ungauged,sites.

A Stochastic Model of Flow Duration Curves

Article

Full-text available

Oct 1993
WATER RESOUR RES

The estimation of flow quantiles is a major focus of current hydrologic research. Probabilistic representations of a few individual quantiles, notably the annual flood and low flow, have been devised, and recently a few of the larger quantiles have been modeled. This research describes and demonstrates the use of a probability model for all flow quantiles in a river. A flow duration curve represents the annual flow frequency characteristics of rivers by depicting the cumulative frequencies for average ranked flows in a river. A model requiring only five parameters is developed, by combining the principles of order statistics and traditional flow frequency analyses, and applied to flow duration curves for rivers in the province of British Columbia, Canada. Streamflows in British Columbia are generated from a number of distinct physical processes operating in highly variable environments. The model presented incorporates the physical generating processes of streamflow in both the statistical representation of flow duration curves and their interpretation.

Regionalized Flow Duration Curves for Philippines

Article

Full-text available

Oct 1983

A regionalization technique is employed to obtain estimates of water availability at ungaged potential small hydropower sites in the Philippines. The flow duration characteristics at representative locations across the country were first parameterized to permit numerical interpolation. Then the geographic variation of one of the parameters was mapped to span the whole archipelago. Using regression, another parameter was expressed as a function of the drainage area. The regionalized map and the regression equation may then be used to synthesize a flow duration curve at an ungaged site. Future modifications of the procedure are suggested as additional data become available.

Regional frequency analysis: A new vocabulary

Article

Full-text available

Jan 1999

Regional frequency analysis solves the problem of estimating the magnitude of extreme events by pooling information from observations at several sites. The topic is reviewed with particular reference to evolution in the last decade. It is suggested that the terminology of regional frequency analysis has lagged behind developments, and a new vocabulary is introduced. This is illustrated for the relevant flood frequency estimation developed for the Flood Estimation Handbook.

Daily flow time series patching or extension: A spatial interpolation approach based on flow duration curves

Article

Full-text available

Dec 1996

An algorithm is described that was initially developed as a simple method for patching and extending observed time series of daily streamflow. It is based on the use of 1-day flow duration curves for each month of the year and on the assumption that flows occurring simultaneously at sites in reasonably close proximity to each other correspond to similar percentage points on their respective duration curves. The algorithm has been incorporated into a model that allows flows at a destination site to be estimated from flows occurring at several source sites. The model has been applied to six groups of catchments within southern Africa and the resulting streamflow simulations compare favourably with those obtained using a semi-distributed, physically-based, daily time step rainfall-runoff model. The current limitations of the approach and its future potential value are discussed.

Estimating the index flood using indirect methods

Article

Full-text available

Jun 2001

Three indirect techniques for index flood estimation are analysed in order to evaluate their applicability and effectiveness. These indirect techniques, based on both statistical and conceptual approaches, are applied to a set of 33 hydrometric stations, located in a large area in northern-central Italy. The results show that the statistical model, due to its flexible structure, has a better descriptive ability than the physically-based models, which are rigidly structured as they conceptualize the rainfall-runoff transformation. However, the rigid structure of the conceptual approaches reduces their dependence on the specific information of the single stations and therefore increases their robustness. Finally, the results highlight that direct estimation techniques could be advisable for catchments with peculiar geomorphoclimatic properties; that is to say properties which differ substantively from those of the majority of the basins considered in the identification of the indirect models. This conclusion seems to hold even when a very limited amount of hydrometric information is available.

Regionalization of Daily Flow Characteristics in Part of the Eastern Cape, South Africa

Article

Full-text available

Dec 1997

A method is described that allows long-term 1-day annual and seasonal flow duration curves at any ungauged location in one of the drainage regions of South Africa to be established. The method is based on normalization of observed flow duration curves by a long-term mean daily flow and subsequent averaging of normalized ordinates of the curves. The estimate of mean daily discharge for an ungauged site is obtained using the information from the existing national data base of flow characteristics. The established set of flow duration curves at a site is further translated into actual daily streamflow time series using a simple nonlinear spatial interpolation technique. Régionalisation des caractéristiques des débits journaliers dans une région du Cap Oriental (Afrique du Sud) Résumé La méthode décrite permet d'établir pour n'importe quel site non jaugé de l'une des régions de drainage d'Afrique du Sud, les courbes des débits journaliers classés annuelles et saisonnières. La méthode est basée sur la normalisation , par le débit journalier moyen, des courbes de débits journaliers classés observées, dont on moyenne ensuite les ordonnées. L'estimation du débit journalier moyen pour un site non jaugé est obtenue à partir de l'information contenue dans la base de données nationale des caractéristiques d'écoulement. Les courbes des débits classés ainsi calculées sont converties en séries temporelles d'écoulement journalier, en utilisant une simple technique d'interpolation spatiale non linéaire.

An analysis of transformations

Article

Jan 1964

“An Analysis of Transformations.”

Article

Jul 1964

In the analysis of data it is often assumed that observations y1, y2, …, yn are independently normally distributed with constant variance and with expectations specified by a model linear in a set of parameters θ. In this paper we make the less restrictive assumption that such a normal, homoscedastic, linear model is appropriate after some suitable transformation has been applied to the y's. Inferences about the transformation and about the parameters of the linear model are made by computing the likelihood function and the relevant posterior distribution. The contributions of normality, homoscedasticity and additivity to the transformation are separated. The relation of the present methods to earlier procedures for finding transformations is discussed. The methods are illustrated with examples.

Duration curves

Article

H.A. Foster

Regional variations in flow-duration curves for rivers in British Columbia, Canada

Article

Jan 1993

A flow-duration curve represents the annual flow-frequency characteristics of rivers by depicting the cumulative frequencies for average ranked flows in a river. Generally the process requires the empirical estimation of the mean flow at each of 365 ranks. A model requiring only five parameters is developed by combining the principles of order statistics and traditional flow-frequency analyses and is applied to flow-duration curves for rivers in the province of British Columbia, Canada. Results from the Model may be interpreted both statistically and physically and allow the identification of hydrologically similar regions. The model presented incorporates the physical generating processes of streamflow in both the statistical representation of flow-duration curves and their interpretation. Similarly, the spatial model presents hydrologic regions that correspond to the known physical environment. -from Authors

Flow-duration curves. 1. New interpretation and confidence-intervals

Article

Jan 1994

Rivers, Form and Process in Alluvial Channels

Article

Jan 1982

Keith Richards

Statistical analysis in hydrology

Article

Jan 1943

L.R. Beard

Applied Linear Regression, 2nd Edition.

Article

Mar 1987

S. Weisberg

Low Flow Estimation in the United Kingdom

Technical Report

Jan 1992

Low Flow Estimation in the United Kingdom. IH Report 108

Technical Report

Jan 1992

Flow‐Duration Curves. I: New Interpretation and Confidence Intervals

Article

Jul 1994

A flow-duration curve (FDC) is simply the complement of the cu-mulative distribution function of daily, weekly, monthly (or some other time interval of) streamflow. Applications of FDCs include, but are not limmited to, hydropower planning, water-quality management, river and reservoir sedimentation studies, habitat suitability, and low-flow augmentation. Although FDCs have a long and rich history in the field of hydrology, they are sometimes criticized because, tra-ditionally, their interpretation depends on the particular period of record on which they are based. If one considers n individual FDCs, each corresponding to one of the individual n years of record, then one may treat those n annual FDCs in much the same way one treats a sequence of annual maximum or annual minimum streamflows. This new annual-based interpretation enables confidence intervals and recurrence intervals to be associated with FDCs in a nonparametric framework.

Applied Linear Regression. by S. Weisberg

Article

Jan 1986
J Roy Stat Soc

C. Chatfield

Assessing the effectiveness of hydrological similarity measures for flood frequency analysis

Article

Oct 2000
J HYDROL

This paper evaluates the relative performance of four hydrological similarity measures that are used to form homogeneous pooling groups for regional frequency analysis. One pair of similarity measures is based on seasonality indexes that re¯ect the timing of extreme events. A further pair of measures considers a characterisation, at the basin scale, of the frequency distribu-tion of rainfall extremes and the extent of the impervious portion of the catchment. The measures are applied to a case study encompassing a large area in Northern-Central Italy. The similarity measures are examined in the context of a pooling scheme that is designed to identify hierarchical, focused pooling groups. The performance of the similarity measures is quanti®ed using a Monte Carlo experiment. The results demonstrate that similarity measures based on seasonality indexes are effective for estimating extreme ¯ow quantiles for the study area. For ungauged catchments, a similarity measure incorporating both rainfall statistics and permeability information is most effective. q 2001 Elsevier Science B.V. All rights reserved.

An Analysis Of Transformations

Article

Jan 1964

Regional Flow-Duration Models for Large Number of Ungauged Himalayan Catchments for Planning Microhydro Projects

Article

Aug 2001

In the Himalayan region of India, most prospective sites for microhydro projects are ungauged and there are insignificant data for analysis. Design flow estimates are made using a regional flow-duration curve. Regional studies on Himalayan watersheds do not appear to have been reported in the literature. Therefore, models are developed for 1,200 ungauged watersheds of the Lower Himalayas. To this end, the region, comparatively larger in size than the catchment, is assumed to be hydrometeorologically homogeneous in its behavior. Formulation of models is based on data transfer between gauged watersheds of the same region, statistical normalization, and empirical regional relation. The performance of a specific model developed for Himachal Pradesh (Region C) is evaluated using the data of 13 watersheds in calibration and 4 watersheds in validation. It is found that the statistical approach of quantile estimation (nondimensional) performs satisfactorily in calibration as well as in validation. The simple power relation for mean flow-estimation, as well as the complete model, performs well in calibration and less satisfactorily in validation because of the short length of data.

Uncertainty Analysis of Regional Flow Duration Curves

Article

Nov 2002

Flow duration curves (FDCs) are useful tools for many water resource development and management purposes. Many water resource projects are located at ungauged sites, however, for which FDCs are required but unavailable due to the lack of observed flow records. Both the polynomial and area-index methods are introduced herein to synthesize FDCs at ungauged sites and estimate their uncertainties for the upper catchments of the Cho-Shuei Creek in Taiwan. The major difference between these two methods is that the area-index method only uses drainage area to explain regional variation, whereas the polynomial method uses annual rainfall, altitude, and drainage area. Results obtained by using cross validation at 15 stations indicate that the polynomial method produces better estimates of synthetic FDCs at ungauged sites than the area-index method. Furthermore, uncertainty analysis through bootstrap resampling reveals that the polynomial method has less uncertainty in synthesizing FDCs than the area-index method.

Magnitude & Frequency of Forces in Geomorphic Processes

Article

Jan 1960

The relative importance in geomorphic processes of extreme or catastrophic events and more frequent events of smaller magnitude can be measured in terms of (1) the relative amounts of "work" done on the landscape and (2) in terms of the formation of specific features of the landscape. For many processes, above the level of competence, the rate of movement of material can be expressed as a power function of some stress, as for example, shear stress. Because the frequency distributions of the magnitudes of many natural events, such as floods, rainfall, and wind speeds, approximate log-normal distributions, the product of frequency and rate, a measure of the work performed by events having different frequencies and magnitudes will attain a maximum. The frequency at which this maximum occurs provides a measure of the level at which the largest portion of the total work is accomplished. Analysis of records of sediment transported by rivers indicates that the largest portion of the total load is carried by flows which occur on the average once or twice each year. As the variability of the flow increases and hence as the size of the drainage basin decreases, a larger percentage of the total load is carried by less frequent flows. In many basins 90 per cent of the sediment is removed by storm discharges which recur at least once every five years. Transport of sand and dust by wind in general follows the same laws. The extreme velocities associated with infrequent events are compensated for by their rarity, and it is found that the greatest bulk of sediment is transported by more moderate events. Many rivers are competent to erode both bed and banks during moderate flows. Observations of natural channels suggest that the channel shape as well as the dimensions of meandering rivers appear to be associated with flows at or near the bankfull stage. The fact that the bankfull stage recurs on the average once every year or two years indicates that these features of many alluvial rivers are controlled by these more frequent flows rather than by the rarer events of catastrophic magnitude. Because the equilibrium form of wind-blown dunes and of wave-formed beaches is quite unstable, the frequency of the events responsible for their form is less clearly definable. However, dune form and orientation are determined by both wind velocity and frequency. Similarly, a hypothetical example suggests that beach slope oscillates about a mean value related in part to wave characteristics generated by winds of moderate speed. Where stresses generated by frequent events are incompetent to transport available materials, less frequent ones of greater magnitude are obviously required. Closer observation of many geomorphic processes is required before the relative importance of different processes and of events of differing magnitude and frequency in the formation of given features of the landscape can be adequately evaluated.

Sediment yield estimation in small watersheds based on streamflow and suspended sediment discharge measurements

Article

May 1997
Soil Tech

In the past, the watershed sediment yield estimation, in rivers where hydrometric information is available, has been done using the sediment rating curve, which is obtained fitting theoretical functions to the water and sediment discharge relationship. Once this relationship is defined, it can be used along with the flow duration curve of a given year (or runoff-frequency data) to obtain the annual sediment yield prediction. Sometimes, specially in recent years, a better estimation has been developed using the same procedure but replacing the flow duration curve for the daily flow series, transforming each daily flow in suspended sediment discharge, by means of the sediment rating curve, and accumulating this information to monthly and annual levels. This procedure is judged adequate for large watersheds, where the differences among the mean daily flow and the maximum and minimum streamflow during the day are not very large. Generally the equations that fit best the sediment rating curves are highly nonlinear, therefore, in small watersheds where the differences among mean daily flows and the extreme instantaneous flows during the day are important, working with mean daily flows (and even worse with flow duration curves) introduces large errors in sediment yield estimations. In addition to this, there also exists other problems related to the previous procedure, namely the extrapolation errors, that can be very important. Also the quality of the basic information is of paramount importance in this type of analysis. This paper discusses all the above problems analyzing case studies related to two important Venezuelans reservoirs: Dos Cerritos in the Tocuyo River and Cumaripa in the Yaracuy river. An evaluation is made of the effects of these sources of errors in the sediment yield estimation of both cases.

Regional flow-duration curves for ungauged sites in Massachusetts

Article

Jan 1992

Regional Flow-Duration Curves at Ungaged Sites in Massachusetts

Article

Jul 1990

A regional hydrologic model is developed for estimating flow-duration curves at ungauged and unregulated basins in Massachusetts. Flow-duration curves often exhibit complex shapes, requiring probability density functions with three or more parameters. This study approximates the lower half of daily flowduration curves using a two-parameter lognormal probability density function. A conjugate gradient algorithm is employed to fit lognormal density functions to the lower half of observed flow-duration curves at 23 basins. Regional regression equations are developed to describe the lognormal model parameters in terms of easily measured basin characteristics. The resulting regional flow-duration model only requires estimates of the watershed area, and a basin relief parameter, both of which are easily obtained from U.S. Geological Survey 7.5-min quadrangle maps. In addition, confidence intervals are derived for flow-duration curves estimated at ungauged sites. A validation experiment reveals that the resulting regional hydrologic model can provide remarkably precise estimates of a flow-duration curve at an ungauged site, considering the simplicity of the model and its ease of application.

Flow duration curves II: a review of applications in water resources planning

Article

Jan 1995

Flow Duration Curve Estimation in Ephemeral Catchments in Portugal

Article

Jun 2003

The flow regime of a river can be described using the flow duration curve (FDC), which represents the frequency distribution of flows and can be derived from gauged data. Many resource assessments are required where gauged data are limited or unavailable, thus models for predicting FDCs in ungauged catchments are required. In semiarid environments, such as parts of southern Portugal, river flows often become zero for significant periods of time. This makes modelling the discontinuities in the flow regime using commonly used continuous distributions more difficult. This paper presents the derivation of a regionalized model (from a data set of 67 catchments) for predicting FDCs for ungauged catchments in Portugal, which may be ephemeral. The approach uses the theory of total probability to combine a model for predicting the percentage of time the river is dry with a model for predicting an FDC for the non-zero period. These component parts can be modelled separately, relating them to catchment characteristics such as hydrogeology and climate.

Flow duration curves II: a review of applications in water resources planning

Article

Dec 1995
J AM WATER RESOUR AS

A streamflow duration curve illustrates the relationship between the frequency and magnitude of streamflow. Flow duration curves have a long history in the field of water-resource engineering and have been used to solve problems in water-quality management, hydropower, instream flow methodologies, water-use planning, flood control, and river and reservoir sedimentation, and for scientific comparisons of streamflow characteristics across watersheds. This paper reviews traditional applications and provides extensions to some new applications, including water allocation, wasteload allocation, river and wetland inundation mapping, and the economic selection of a water-resource project.

Regional Analysis of Flow Duration Curves for a Limestone Region

Article

Jun 1996

The methodology proposed permits the regional analysis of that part of the duration curve which refers to droughts. It only requires (1) the definition of an equation, characterised by a set of parameters, describing the lower part of the duration curve and (2) the identification of a suitable number of statistical regional laws enabling the parameters of the selected equation to be calculated in any location where no direct discharge measurements are available. An application of the methodology to a case of the real world is then described. It refers to the Molise Region (Italy) where the effect of outcropping limestone complexes heavily influences the low flow characteristics.

Regionalization of Flow Duration Characteristics

Article

Nov 1985
J HYDROL

The flow duration curve is regionalized by using morphoclimatic characteristics of the drainage basin. The monthly flow duration characteristics at eleven major flow measuring sites across the western and northwestern regions of Greece were first parameterized. Using multiple regression techniques, the geographic variation of each parameter of the best fitted flow duration model is explained in terms of the mean annual areal precipitation, the drainage area, the hypsometric fall and the length of the main river course from the divide of the basin to the site of interest. The regionalized regression equations are successfully used to synthesize flow duration curves at other locations within the hydrologically homogeneous regions of western and northwestern Greece. The method is useful in obtaining estimates of water availability for hydropower at ungaged sites (especially for small hydropower plants, for run-of-river plants), or for other water resources development (water supply, water quality projects), within the regions studied, where the main governmental interest for water resources development is focused.

Low Flow Hydrology: A Review

Article

Jan 2001
J HYDROL

Vladimir Smakhtin

The paper intends to review the current status of low-flow hydrology — a discipline which deals with minimum flow in a river during the dry periods of the year. The discussion starts with the analysis of low-flow generating mechanisms operating in natural conditions and the description of anthropogenic factors which directly or indirectly affect low flows. This is followed by the review of existing methods of low-flow estimation from streamflow time-series, which include flow duration curves, frequency analysis of extreme low-flow events and continuous low-flow intervals, baseflow separation and characterisation of streamflow recessions. The paper describes the variety of low-flow characteristics (indices) and their applications. A separate section illustrates the relationships between low-flow characteristics. The paper further focuses on the techniques for low-flow estimation in ungauged river catchments, which include a regional regression approach, graphical representation of low-flow characteristics, construction of regional curves for low-flow prediction and application of time-series simulation methods. The paper presents a summary of recent international low-flow related research initiatives. Specific applications of low-flow data in river ecology studies and environmental flow management as well as the problem of changing minimum river flows as the result of climate variability are also discussed. The review is largely based on the research results reported during the last twenty years.

An Analysis of Transformation

Article

Jan 1964
Stat

River Flow Forecasting Through Conceptual Models: Part 1. — A Discussion of Principles

Article

Apr 1970
J HYDROL

The principles governing the application of the conceptual model technique to river flow forecasting are discussed. The necessity for a systematic approach to the development and testing of the model is explained and some preliminary ideas suggested.

The Jackknife and The Bootstrap

Article

Sep 1997

This chapter deals with statistical methods that, in some way, avoid mathematical difficulties that one would be facing using traditional approaches. The traditional approach of mathematical statistics is based on analytic expressions, or formulas, so avoiding these might seem itself a formidable task, especially in view of the chapters that so far have been covered. It should be pointed out that we have no objection of using mathematical formulas—in fact, some of these are pleasant to use. However, in many cases, such formulas are simply not available or too complicated to use.

Probabilistic flow duration curves for use in environmental planning and management In: Harmancioglu NB, et al, editors. Integrated approach to environmental data [19] Regionalised flow duration curves for Philippines

Jan 1983
320-30

P Claps
Fiorentino
Rg Quimpo
Aa Alejandrino
Mcnally

Claps P, Fiorentino M. Probabilistic flow duration curves for use in environmental planning and management. In: Harmancioglu NB, et al, editors. Integrated approach to environmental data [19] Quimpo RG, Alejandrino AA, McNally TA. Regionalised flow duration curves for Philippines. J Water Resour Plann Manage ASCE 1983;109(4):320–30.

Estimated flow-duration curves for selected ungaged sites in Kansas

S E Studley

Studley SE. Estimated flow-duration curves for selected ungaged sites in Kansas. US Geological Survey. Water-resources investigations report 01-4142, 2001.

Probabilistic flow duration curves for use in environmental planning and management In: Harmancioglu NB, et al, editors. Integrated approach to environmental data methods

953-965

P Claps
Fiorentino

Claps P, Fiorentino M. Probabilistic flow duration curves for use in environmental planning and management. In: Harmancioglu NB, et al, editors. Integrated approach to environmental data methods.Hydrol SciJ 964 A. Castellarin et al. / Advances in Water Resources 27 (2004) 953–965 rmanagement systems. NATO-ASI series 2(31). Dordrecht, The Netherlands: Kluwer. p. 255–66.

Manual of hydrology, 2, low flow techniques, flow-duration curves. US Geol Surv Water Supply Pap 1542-A

J C Searcy

Searcy JC. Manual of hydrology, 2, low flow techniques, flow-duration curves. US Geol Surv Water Supply Pap 1542-A, 1959.

A hydro-climatological model of daily streamflows for the northeast United States

N M Fennessey

Fennessey NM. A hydro-climatological model of daily stream-flows for the northeast United States. PhD dissertation, Tufts University, Medford, MA, 1994.

Regional frequency analysis: a new vocabulary In: Hydrological extremes: understanding, predicting, mitigating

Jan 1999
237-43

Reed Dw
Robinson Aj Faulkner
Ds
Stewart
Ej

Reed DW, Jakob D, Robinson AJ, Faulkner DS, Stewart EJ. Regional frequency analysis: a new vocabulary. In: Hydrological extremes: understanding, predicting, mitigating, Proc IUGG 99 Symposium. Birmingham, IAHS, Publ. no. 255, 1999. p. 237–43.

Kansas streamflow characteristics-part 1-Flow duration

L W Furness

Furness LW. Kansas streamflow characteristics-part 1—Flow duration. Kansas Water Resources Board technical report no. 1, 1959. 213 p.

Regional Flow-Duration Curves: Reliability for Ungauged Basins

Abstract

No full-text available

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Flow‐Duration Curves. I: New Interpretation and Confidence Intervals