Recession Parameters Research Articles

Estimating source regions for snowmelt runoff in a Rocky Mountain basin: tests of a data‐based conceptual modeling approach

AbstractIn many mountain basins, river discharge measurements are located far away from runoff source areas. This study tests whether a basic snowmelt runoff conceptual model can be used to estimate relative contributions of different elevation zones to basin‐scale discharge in the Cache la Poudre, a snowmelt‐dominated Rocky Mountain river. Model tests evaluate scenarios that vary model configuration, input variables, and parameter values to determine how these factors affect discharge simulation and the distribution of runoff generation with elevation. Results show that the model simulates basin discharge well (NSCE and R >0.90) when input precipitation and temperature are distributed with different lapse rates, with a rain‐snow threshold parameter between 0 and 3.3 °C, and with a melt rate parameter between 2 and 4 mm °C−1 d−1 because these variables and parameters can have compensating interactions with each other and with the runoff coefficient parameter. Only the hydrograph recession parameter can be uniquely defined with this model structure. These non‐unique model scenarios with different configurations, input variables, and parameter values all indicate that the majority of basin discharge comes from elevations above 2900 m, or less than 25% of the basin total area, with a steep increase in runoff generation above 2600 m. However, the simulations produce unrealistically low runoff ratios for elevations above 3000 m, highlighting the need for additional measurements of snow and discharge at under‐sampled elevations to evaluate the accuracy of simulated snow and runoff patterns. Copyright © 2013 John Wiley & Sons, Ltd.

Ecosystem processes at the watershed scale: Hydrologic vegetation gradient as an indicator for lateral hydrologic connectivity of headwater catchments

Lateral water flow in catchments can produce important patterns in water and nutrient fluxes and stores and also influences the long‐term spatial development of forest ecosystems. Specifically, patterns of vegetation type and density along hydrologic flow paths can represent a signal of the redistribution of water and nitrogen mediated by lateral hydrologic flow. This study explores the use of emergent vegetation patterns to infer ecohydrologic processes and feedbacks in forested headwater catchments. We suggest a hydrologic gradient of vegetation density as an indicator of lateral connectivity within headwater catchments. We define the hydrologic vegetation gradient (HVG) as the increase of normalized difference vegetation index per unit increase of the topographic wetness index. HVG are estimated in different headwater catchments in the Coweeta Hydrologic Laboratory using summer IKONOS imagery. We use recession slope analysis with gauge data and a distributed ecohydrological model to characterize the patterns of seasonal flow regimes within the catchments. Correlations between HVG, catchment runoff, early recession parameters, and model parameters show the interactive role of vegetation and lateral hydrologic connectivity of systems in addition to climatic and geomorphic controls. This suggests that HVG effectively represents the level of partitioning between localized water use and lateral water flow along hydrologic flow paths, especially during the growing season. It also presents the potential to use simple remotely sensed hydrologic vegetation gradients as an indicator of lateral hydrologic connectivity to extrapolate recession behavior and key model parameters of distributed hydrological models for ungauged headwater catchments.

The Use of the Recession Index as Indicator for Components of Flow

Hydrograph recession analysis is widely used in hydrological research and water resources planning and management. The most common application is the forecasting of low flows, estimating groundwater resources in a catchment, rainfall runoff models and hydrograph analysis. In the rainfall runoff modelling, some authors have included the recession characteristics in their model. They used the recession parameter for hydrograph separation and modelling surface runoff.This paper presents an alternative commonly used techniques for hydrograph recession analysis, namely of an individual recession segment, the master recession and a relatively recent approach based on wavelet transform was carried out in order to separate analytically the linear component hydrographs by recession index K that is commonly used as an indicator of flow. These methods were applied to a set of measures hydrometric the North-eastern Algeria in the watershed Seybouse. The results show that all the methods tested produce reasonable and comparable results.

Parameter-dependent convergence bounds and complexity measure for a class of conceptual hydrological models

We provide analytical bounds on convergence rates for a class of hydrologic models and consequently derive a complexity measure based on the Vapnik–Chervonenkis (VC) generalization theory. The class of hydrologic models is a spatially explicit interconnected set of linear reservoirs with the aim of representing globally nonlinear hydrologic behavior by locally linear models. Here, by convergence rate, we mean convergence of the empirical risk to the expected risk. The derived measure of complexity measures a model's propensity to overfit data. We explore how data finiteness can affect model selection for this class of hydrologic model and provide theoretical results on how model performance on a finite sample converges to its expected performance as data size approaches infinity. These bounds can then be used for model selection, as the bounds provide a tradeoff between model complexity and model performance on finite data. The convergence bounds for the considered hydrologic models depend on the magnitude of their parameters, which are the recession parameters of constituting linear reservoirs. Further, the complexity of hydrologic models not only varies with the magnitude of their parameters but also depends on the network structure of the models (in terms of the spatial heterogeneity of parameters and the nature of hydrologic connectivity).

Automated Linear and Nonlinear Reservoir Approaches for Estimating Annual Base Flow

Three automated base flow separation techniques based on linear and nonlinear reservoir approaches are used to identify the seasonal variation of base flow and to quantify the annual base flow for three subwatersheds of the Essex region in Southwestern Ontario, Canada. Significant differences in annual base flow estimated by linear and nonlinear reservoir algorithms are observed. In the nonlinear reservoir approach, the recession parameter is considered to be a seasonally variable parameter. The nonlinear reservoir approach fits streamflow recession better than the linear reservoir approach. The steeper slopes of seasonal flow duration curves in the 90% to 100% flow exceedance range show that the groundwater contribution to streamflow is relatively small in the study area. The precipitation-streamflow relationships show faster response of base flow during the period of high recharge. All of the methods show similar base flow estimation during the period of high evapotranspiration losses. The nonlinear reservoir approach represents the base flow response to precipitation better than the other methods. Therefore, the annual base flow estimated by the nonlinear reservoir approach is considered as the most reasonable estimation for the formulation of water budget of the study area. The method quantifies the occurrence of average annual baseflow as 34% of average annual streamflow.

Nonlinear baseflow recession analysis in watersheds with intermittent streamflow

Discharge in most rivers consists mainly of baseflow exfiltrating from shallow groundwater reservoirs, while surface or other direct flows cease soon after rain storms or snowmelt. Analysis of observed baseflow recessions of two rivers in Turkey with intermittent flows and different geographical and climatic characteristics yielded nonlinear storage–outflow relationships of the highly seasonal aquifers. Baseflow separation was carried out using a nonlinear reservoir algorithm. Baseflow seasonality is related to the hydro-climatic conditions influencing groundwater recharge and evapotranspiration of groundwater. As intermittent streams generally have zero flows in the dry season, calibration of recession parameters is in many cases a complicated task. Citation Aksoy, H. & Wittenberg, H. (2011) Nonlinear baseflow recession analysis in watersheds with intermittent streamflow. Hydrol. Sci. J. 56(2), 226–237.

On the base flow recession at the Panola Mountain Research Watershed, Georgia, United States

There are two types of nonlinearity for recession slope curves: (1) the data cloud of observed ln(–dQ/dt) versus ln(Q) along a straight line where the slope is not equal to 1, and (2) the data cloud of observed ln(–dQ/dt) versus ln(Q) is concave or convex. From the 0.1 ha hillslope, the 10 ha headwater subwatershed, and the 41 ha watershed at the Panola Mountain Research Watershed (PMRW), the observed ln(–dQ/dt) versus ln(Q) changes from convex to concave. This has been explained by the spatial heterogeneity of recession properties and nonlinearity of hillslope hydraulics. Hillslope bedrock leakage and return flow to the perennial riparian zone aquifer are important factors affecting the ln(–dQ/dt) versus ln(Q) relations, and an assessment of this mechanism for explaining the observed base flow recessions at the PMRW is the sole focus of this research. As a result, the lower envelope and the upper envelope should be used to estimate the recession parameters for the 0.1 ha hillslope and the 41 ha watershed, respectively, and the recession at the 10 ha watershed is a mixture of them. Based on the recession analysis, the leakage to the bedrock on the hillslope and return flow to the perennial stream riparian groundwater can be estimated, and the estimation can be verified by other studies.

Recession slope curve analysis under human interferences

To study the base flow recession at the watershed scale, the log-scale plot of − dQ/ dt ∼ Q proposed by Brutsaert and Nieber [10] has been used to estimate the recession parameters, i.e., the slope and interception of the theoretical recession slope curve. The lower envelope or the best fit in some studies is usually used to determine the recession slope curve for natural watersheds. However, human interferences exist in most watersheds around the world. This paper discusses the impact of human interferences, which include groundwater pumping, water diversion and return flow, on the determination of the recession slope curve and the cloud shape of the data points of − dQ/ dt ∼ Q. First, values of − dQ/ dt generated for hypothetical watersheds are analyzed. Then real data for three watersheds in Illinois is analyzed to verify the hypothetical analysis. The placement of the recession slope curve depends on the coexistence and relative amount of the evapotranspiration, groundwater pumping or even water diversion if it exists, and the return flow. When the water consumption rate is small, the recession slope curve can even be located at the upper envelope of the cloud of points representing historical data. These results suggest that the use of the lower envelope as a guideline for estimating recession parameters for watersheds subject to human interferences can result in biased estimates.

Salinograph trends as indicators of the recession characteristics of stream components

AbstractCompared to hydrograph recession analysis, which is widely applied in engineering hydrology, the quantitative assessment of stream salinity with time (i.e. the salinograph) has received significantly less attention. In particular, while in many previous hydrological studies an inverse relationship between hydrograph and salinograph responses is apparent, the concept of salinity accession (the inversely related salinity counterpart to hydrograph recession) has not been introduced nor quantitatively evaluated in previous literature. In this study, we conduct a mathematical analysis of salinograph accession, and determine new quantitative relationships between salinity accession and hydrograph recession parameters. An equation is formulated that reproduces the general trend in salinity accession. A salinity accession parameter kc is then introduced and is shown to be the ratio of direct runoff to total stream flow recession parameters: kr/k. The groundwater recession parameter kg was estimated using a simple and rapid method that uses both salinograph and hydrograph data. Salinity accession type‐curves illustrate that under certain conditions, the relative steepness of individual salinographs is dependent upon the ratio of groundwater salinity to direct runoff salinity: Cg/Cr. The salinity accession algorithms are applied to two contrasting field settings: Scott Creek, South Australia and Sandy Creek, northern Queensland, Australia. It was found that kg > k during periods of obvious stream flow recession, for the events analysed. Salinograph accession behaviour was fairly similar for both sites, despite contrasting environments. Using assumed end‐member salinities for groundwater and direct runoff based upon field observations, the behaviour of kc from the Scott Creek site was approximately reproduced by varying the initial groundwater to runoff flow ratio: Qg0/Qr0, within reasonable parameter ranges. The use of salinograph information when used in addition to standard hydrograph analyses provided useful information on recession characteristics of stream components. Copyright © 2008 John Wiley & Sons, Ltd.

Statistical Models and the Estimation of Low Flows

he present paper provides a brief review of statistical models that are commonly used in the estimation of low flows both at sites with a reliable streamflow record and sites remote from data sources. Opportunities are identified for the regional estimation of low-flow characteristics at ungauged sites. The adaptation of the neighbourhood regionalization approach, commonly used in regional flood frequency analysis, can be extended to low-flow variables. Estimation approaches extending the usefulness of recession information in regional low-flow frequency analysis to ungauged sites using a canonical correlation analysis approach for the identification of hydrological neighbourhoods is described. The validity of recession parameters when estimated from very short hydrological data records is also discussed. Promising new directions for future research in the field of statistical low-flow frequency estimation are identified.

Periodontal assessment of postmenopausal women receiving risedronate

The purpose of this study was to compare periodontal status of postmenopausal women with mild to moderate osteoporosis who use risedronate therapy with those who do not. In this cross-sectional study, a total of 60 age-matched postmenopausal women with mild to moderate osteoporosis diagnosed by a bone density scan T score below -2.5 at either spine or hip were divided into two groups. Women in the experimental group had used systemic risedronate once weekly (35 mg) for at least 3 months. Women in the control group had never used bisphosphonate therapy. The periodontal status of each subject was evaluated through a clinical periodontal examination including evaluation of periodontal probing depth, gingival recession, gingival index, plaque score, attachment loss, and alveolar bone level. The significance in differences between the two groups was assessed using two-tailed paired t tests. Significant differences (P < 0.05) were found between risedronate and control groups for periodontal probing depth (2.6 vs 2.9 mm), gingival index (0.37 vs 0.71), plaque score (56.2 vs 77.0), attachment loss (2.8 vs 3.2 mm), and alveolar bone level (3.1 and 4.0), respectively. Gingival recession parameters did not differ significantly. Five of six periodontal parameters evaluated show that postmenopausal women with mild to moderate osteoporosis using risedronate therapy have healthier periodontal status than those who do not use bisphosphonates. Women using risedronate therapy show significantly less plaque accumulation, less gingival inflammation, lower probing depths, less periodontal attachment loss, and greater alveolar bone levels. These observations suggest that risedronate therapy may play a beneficial role in periodontal status.

Models for recession flows in the upper Blue Nile River

AbstractStream‐flow recessions are commonly characterized by the exponential equation or in the alternative power form equation of a single linear reservoir. The most common measure of recession is the recession constant K, which relates to the power function form of the recession equation for a linear reservoir. However, in reality it can be seen that the groundwater dynamics of even the simplest of aquifers may behave in a non‐linear fashion. In this study three different storage–outflow algorithms; single linear, non‐linear and multiple linear reservoir were considered to model the stream‐flow recession of the upper Blue Nile. The recession parameters for the linear and non‐linear models were derived by the use of least‐squares regression procedures. Whereas, for the multiple linear reservoir model, a second‐order autoregressive AR (2) model was applied first in order to determine the parameters by the least‐squares method. The modelling of the upper Blue Nile recession flow performed shortly after the wet season, when interflow and bank storage may be contributing considerably to the river flow, showed that the non‐linear reservoir model simulates well with the observed counterparts. The variation related to preceding flow on a recession parameter of the non‐linear reservoir remains significant, which was obtained by stratification of the recession curves. Although a similar stratification did not show any systematic variation on the recession parameters for the linear and multiple linear reservoir models. Copyright © 2004 John Wiley &amp; Sons, Ltd.

A comparison of techniques for hydrograph recession analysis

AbstractA comparison between commonly used techniques for hydrograph recession analysis, namely the semi‐logarithmic plot of a single recession segment, the master recession and a relatively new approach based on wavelet transform was carried out. These methods were applied to a number of flood hydrograph events of two catchments in West Java, Indonesia. The results show that all the methods tested produce reasonable and comparable results. However, problems arise in the semi‐logarithmic plot and the master recession, i.e. determining the recession parameter K is not an easy task especially where the plotted data on a semi‐logarithmic plot is not a linear but a curved line. On a curved line, the end of direct flow or starting point of baseflow is not clear and it is quite difficult to identify. Hence, the best line as a basis for computing the recession parameter K becomes uncertain. The wavelet transform approach, however, produces promising results and minimizes a number of problems associated with hydrograph recession analysis. The end of direct flow and the location of the baseflow component are easily determined through the wavelet maps. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Recession flow analysis of the Blue Nile River

AbstractEstimates of the amount of recession flow can be derived from streamflow records. Such estimates are critical in the assessment of low flow characteristics for the Blue Nile River, from which about two‐thirds of the irrigation requirements in Sudan are satisfied. The recession flow hydrograph can be estimated by fitting the conceptual non‐linear storage outflow model using an iterative algorithm. An analytical model to forecast the Blue Nile recession flow is developed and the performance of the model is compared to the previous Blue Nile recession flow model. In the proposed model, a simple linear regression equation is introduced to illustrate the effect of antecedent flow on the recession parameter. Results indicate that the model can provide a simple and reliable method to predict the recession flow of the Blue Nile River. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Modelling the subsurface flow component in the runoff recession phase by means of a linear and non-linear reservoir models

The paper deals with the time variability of the subsurface water storage depletion. The analysis was carried out in a small experimental basin in the Jizera Mountains, Czech Republic. The research focused on the hydro graph falling limbs - recession curves - which were selected from daily runoff series using various selection criteria. These criteria include a requirement that a curve should represent subsurface flow which is not increased by surface runoff. The selected measured recession curves are modelled by means of the exponential and hyperbolical law of depletion. The time variability of the recession curves is quantified by the variability of the modelled recession parameters. 22 variables representing antecedent climate and runoff conditions as well as the conditions during the recession period were defined for the examination of possible causing factors of the recession curve time variability. The correlation analysis and the multivariate statistical methods were applied.

Recession parameters versus cosmic time

Theoretical relations for such recession parameters as the Earth–galaxy (L) and Earth–photon (Lp) separation distances, Hubble parameter (H), universe density ratio (Ω), scale factor (R), and expansion factor distance (A) are given as functions of cosmic time (t). These relations are based on the standard flat, closed, and open models of the universe with the Einstein cosmological constant Λ=0. Comparisons are made of these models using selected values of Ho and Ωo, which for each model indicate an age of the universe that is consistent with ages reported for the oldest stars.

Estimation of baseflow recession constants

Hydrograph recession constants are required in rainfall-runoff models, baseflow augmentation studies, geohydrologic investigations and in regional low-flow studies. The recession portion of a streamflow hydrograph is shown to be either an autoregressive process or an integrated moving average process, depending upon the structure of the assumed model errors. Six different estimators of the baseflow recession constant are derived and tested using thousands of hydrograph recessions available at twenty-three sites in Massachusetts, U.S. When hydrograph recessions are treated as an autoregressive process, unconditional least squares or maximum likelihood estimators of the baseflow recession constant are shown to exhibit significant downward bias due to the short lengths of hydrograph recessions. The precision of estimated of hydrograph recession constants is shown to depend heavily upon assumptions regarding the structure of the model errors. In general, regression procedures for estimating hydrograph recession parameters are generally preferred to the time-series alternatives. An evaluation of the physical significance of estimates of the baseflow recession constant is provided by comparing regional regression models which relate low-flow statistics to three independent variables: drainage area, basin slope and the baseflow recession constant. As anticipated, approximately unbiased estimators of the baseflow recession constant provide significant information regarding the geohydrologic response of watersheds.

A review of baseflow recession analysis

Recession analysis is a well-known tool in hydrological analysis. Its application, however, poses many methodical questions, and throughout the literature numerous solutions have been sought. The quantification of the recession curve involves the selection of an analytical expression, derivation of a characteristic recession and optimization of the recession parameters. A major problem is the high variability encountered in the recession behaviour of individual segments. The segments represent different stages in the outflow process, and a physically based short-term or seasonal influence on the recession rate adds to the problem of deriving a characteristic recession. This paper discusses these elements of recession analysis and reviews different ways of characterizing the baseflow recession rate.

Parameter uncertainty and simulation of design floods in Sweden

This paper examines the effects of parameter uncertainty on the simulation of recorded floods and design floods, using the HBV hydrological model. Two Swedish catchments with hydropower development were studied. A Monte Carlo procedure was used to generate parameter sets of different levels of uncertainty. The results showed that the most sensitive parameters in the calibration process were the snowfall correction factor and the recession parameters. Furthermore, when the model was extrapolated to simulate design flood and water stage hydrographs, the single most sensitive parameter was the highest recession coefficient. In addition, it was found that parameter uncertainty was associated with combinations of parameters rather than the absolute values of each.