Using a parsimonious rainfallrunoff model to detect non-stationarities in the hydrological behaviour of watersheds (original) (raw)
A distribution-free test to detect gradual changes in watershed behavior
Water Resources Research, 2003
This paper presents a distribution-free statistical test aimed at detecting gradual changes in the hydrological behavior of watersheds. The proposed test uses a rainfall-runoff model to identify watershed behavior over successive time periods and a resampling approach to quantify the significance of trends. The method can be applied with any model deemed suitable for the studied watershed. To assess test efficiency, we used three different case studies: An afforested agricultural watershed, a burnt-over forested watershed, and a watershed covered by old-growth forest. All three watersheds had a long period of rainfall and runoff records (60, 35, and 40 years, respectively), on which stationarity could be tested. The test was shown to adequately detect gradual changes, and it can therefore be useful to identify hydrological trends, wherever rainfall and streamflow time series are available.
Watershed models for assessment of hydrological behavior of the catchments: a comparative study
Water Practice and Technology, 2020
Hydrological parameters like overland flow, soil loss and nutrient losses can be studied by using different watershed models. However, all these models vary significantly in their analysis of parameters, input and output flexibility, scale accountability, processing ability, computational efficiency and capability of modeling the changes in catchments. This paper reviews different watershed models used for analyzing overland flow, soil loss and sediment yield with their shortcomings and strengths. These watershed models are described briefly along with their capabilities and shortcomings with their examples of applications, results and comparisons. An outcome of these discussions is presented in tabular format as a screening tool to allow the researchers and decision makers to choose the appropriate watershed model for the specific purpose.
Consistency of Hydrologic Relationships of a Paired Watershed Approach
American Journal of Climate Change, 2013
Paired watershed studies are used around the world to evaluate and quantify effects of forest and water management practices on hydrology and water quality. The basic concept uses two neighboring watersheds (one as a control and another as a treatment), which are concurrently monitored during calibration (pre-treatment) and post-treatment periods. A statistically significant relationship between the control and treatment watersheds is established during calibration period such that any significant shift detected in the relationship during treatment is attributed to the treatment effects. The approach assumes that there is a consistent, quantifiable, and predictable relationship between watershed response variables. This study tests the hypothesis that the hydrologic relationships between control and treatment watersheds for daily water table elevation (WTE) and daily flow data were similar without any statistically significant difference during two different calibration (1988-1989 and 2007-2008) and treatment periods (1995-1996 and 2009), when the control and treatment watersheds were interchanged. The watersheds are two artificially drained loblolly pine forests (D1: 24.7 ha and D2: 23.6 ha) located in coastal North Carolina. Results depicted significantly similar WTE regression relationships during the two calibration periods but significantly different WTE relationships during the two treatment periods with reversed control and treatment watersheds. Calibration and treatment flow relationships, and the mean treatment effects on WTE and flow, before and after treatment reversal were significantly different (α = 0.05). The study also discusses causes of differences in hydrologic relationships and treatment effects for such reversal of treatments during a 21-year span of the study on these two similar and adjacent watersheds. The observed differences in the hydrologic relationships between control and treatment watersheds before and after treatment reversal may be attributed to climate or hydrologic non-stationarity which may affect the reliability of paired watershed approach especially when the calibration periods are short. 153 a Total rainfall in millimeters with the daily mean and its 95% confidence value in square brackets; b Number of days. Sample size may be less than number of days due to missing data. AJCC 155
Hydrologic regime characterization for a semi-arid watershed
Die Bodenkultur, 2011
The European Water Framework Directive (WFD) constitutes a new view of water resources management in Europe, based mainly upon ecological elements. Its final objective is to achieve at least a "good chemical and ecological quality status" for all water bodies by 2015. To attain a good ecological status, aquatic systems must not diverge remarkably from reference (natural) conditions. Thus, information describing the hydrological regime is likely to be of the utmost importance for the implementation of the WFD, since it is implicit that this may be responsible for the ecological status. The hydrological regime of a river, in fact, plays a major role in determining the biotic composition, structure, and function of aquatic and riparian ecosystem. The analysis of the hydrological regime is particularly relevant for non permanent rivers since it varies on a spatial and temporal scale depending on precipitation patterns and is severely altered by flash floods.
2022
Climate change and human activities are two major drivers that alter hydrological cycle processes and cause changes in spatio-temporal distribution of water availability. Streamflow as the most important component of hydrologic cycle is expected to be influenced by climate change as well as human activities. Three methods of hydrological sensitivity, slope change ratio of cumulative quantity and hydrologic modeling by SWAT are investigated and compared for separating the impact of climate change and human activities on the Minab River flow in south of Iran. Also, nine scenarios are defined for development of agricultural land and urbanization to evaluate the effect of climate change and human activities within the SWAT model. Mann-Kendall and Pettitt tests are used to analyze the trends and the change point in the climatic data time series. Results show that the share of human activities and climate change are close in three methods. Scenario H9 that includes the development of agricultural land and urbanization by 30% compared to the present situation reduced the streamflow by 88.8% that is the highest reduction among the scenarios. Also, the results indicate that human activities are the main reason for streamflow reduction in the Minab River.
Water, 2020
Depending on the purpose of the study, aggregated hydrological models are preferred over distributed models because they provide acceptable results in terms of precision and are easy to run, especially in data scarcity scenarios. To obtain acceptable results in terms of hydrological process representativeness, it is necessary to understand and assess the models. In this study, the relative importance of the parameters of the Hydrologiska Byråns Vattenbalansavdelning (HBV) model is analyzed using sensitivity analysis to detect if the simulated processes represent the predominant hydrological processes at watershed scale. As a case study, four watersheds with different hydrological regimes (glacial and pluvial) and therefore different dominant processes are analyzed. The results show that in the case of the rivers with a glacial regime, the model performance depends highly on the snow module parameters, while in the case of the rivers with a pluvial regime, the model is sensitive to t...
Application of selected statistical tests to detect changes in the rainfall and runoff regime
Bodenkultur, 2011
The research discusses the analysis of trends of essential hydrometeorological elements using selected statistical methods. The main aim of our research project was to compare the time series of flows with an adequate series of rainfall values; air temperatures and snow cover depths, and thereby try to determine what kind of changes occur in low mountains areas (study areas: Bohemian Forest, Ore Mountains, Jeseniky Mt.). We verified the absolute and relative homogeneity of the data series, as well as the presence of a trend in the data series. The following statistical tests, in particular, were used for this purpose: Pettitt test; Standard Normal Homogeneity test; two Wilcoxon tests; and a Mann-Kendall test. Simple-mass and double-mass curves of monthly and annual values were also applied in the case of flow and rainfall values; furthermore, quarter-year as well as cold and warm half-year periods were studied. Trends in flow development do not highly correspond to rainfall tendencies. Since the end of the 70s and especially in the 80s (Bohemian Forest and Jeseniky Mt. and later in 90s Ore Mt.), a substantial increase in runoff occurred during the winter months. Starting in 1980, average annual temperatures have been rising, which corresponds very well to a reduction in snow cover.
Detection of hydrologic trends and variability
Journal of Hydrology, 2002
This paper describes the development and application of a procedure that identi®es trends in hydrologic variables. The procedure utilizes the Mann±Kendall non-parametric test to detect trends, a permutation approach to estimate the test distribution, and accounts for the correlation structure in the data in determining the signi®cance level of the test results. The research investigates 18 hydrologic variables that re¯ect different parts of the hydrologic cycle. The hydrologic variables are analyzed for a network of 248 Canadian catchments that are considered to re¯ect natural conditions. A selection of catchments identi®ed to have trends in hydrologic variables is studied further to investigate the presence of trends in meteorological variables and the relationship between the hydrologic and the meteorological response to climatic change. It is concluded that a greater number of trends are observed than are expected to occur by chance. There are differences in the geographic location of signi®cant trends in the hydrologic variables investigated implying that impacts are not spatially uniform. q
A strategy for diagnosing and interpreting hydrological model nonstationarity
Water Resources Research, 2014
This paper presents a strategy for diagnosing and interpreting hydrological nonstationarity, aiming to improve hydrological models and their predictive ability under changing hydroclimatic conditions. The strategy consists of four elements: (i) detecting potential systematic errors in the calibration data; (ii) hypothesizing a set of ''nonstationary'' parameterizations of existing hydrological model structures, where one or more parameters vary in time as functions of selected covariates; (iii) trialing alternative stationary model structures to assess whether parameter nonstationarity can be reduced by modifying the model structure; and (iv) selecting one or more models for prediction. The Scott Creek catchment in South Australia and the lumped hydrological model GR4J are used to illustrate the strategy. Streamflow predictions improve significantly when the GR4J parameter describing the maximum capacity of the production store is allowed to vary in time as a combined function of: (i) an annual sinusoid; (ii) the previous 365 day rainfall and potential evapotranspiration; and (iii) a linear trend. This improvement provides strong evidence of model nonstationarity. Based on a range of hydrologically oriented diagnostics such as flow-duration curves, the GR4J model structure was modified by introducing an additional calibration parameter that controls recession behavior and by making actual evapotranspiration dependent only on catchment storage. Model comparison using an information-theoretic measure (the Akaike Information Criterion) and several hydrologically oriented diagnostics shows that the GR4J modifications clearly improve predictive performance in Scott Creek catchment. Based on a comparison of 22 versions of GR4J with different representations of nonstationarity and other modifications, the model selection approach applied in the exploratory period (used for parameter estimation) correctly identifies models that perform well in a much drier independent confirmatory period. Key Points: A strategy to diagnose and interpret hydrological nonstationarity is presented Time-varying parameters are used to represent model nonstationarity The strategy reduces predictive biases over an independent confirmatory period Correspondence to: S. Westra, seth.westra@adelaide.edu.au Citation: Westra, S., M. Thyer, M. Leonard, D. Kavetski, and M. Lambert (2014), A strategy for diagnosing and interpreting hydrological model nonstationarity, Water Resour. Res., 50, 5090-5113,
Runoff regime estimation at high-elevation sites: a parsimonious water balance approach
Hydrology and Earth System Sciences, 2011
We develop a water balance model, parsimonious both in terms of parameterization and of required input data, to characterize the average runoff regime of high-elevation and scarcely monitored basins. The model uses a temperature threshold to partition precipitation into rainfall and snowfall, and to estimate evapotranspiration volumes. The role of snow in the transformation of precipitation into runoff is investigated at the monthly time scale through a specific snowmelt module that estimates melted quantities by a non-linear function of temperature. A probabilistic representation of temperature is also introduced, in order to mimic its sub-monthly variability. To account for the commonly reported rainfall underestimation at high elevations, a two-step precipitation adjustment procedure is implemented to guarantee the closure of the water balance. The model is applied to a group of catchments in the North-Western Italian Alps, and its performances are assessed by comparing measured and simulated runoff regimes both in terms of total bias and anomalies, by means of a new metric, specifically conceived to compare the shape of the two curves. The obtained results indicates that the model is able to predict the observed runoff seasonality satisfactorily, notwithstanding its parsimony (the model has only two parameters to be estimated). In particular, when the parameter calibration is performed separately for each basin, the model proves to be able to reproduce the runoff seasonality. At the regional scale (i.e., with uniform parameters for the whole region), the performance is less positive, but the model is still able to discern among different mechanisms of runoff formation that depend on the role of the snow storage. Because of its parsimony and the robustness in the approach, the model is suitable for application in ungauged basins and for large scale investigations of the role of climatic variables on water availability and runoff timing in mountainous regions.
Trend Assessment in Rainfall-Runoff Behavior in Urbanizing Watersheds
Journal of Hydrologic Engineering, 2002
A typical flood frequency analysis is based on gauged annual maximum discharges. One assumption behind the analysis is that the measured discharge signal is stationary. The validity of this assumption can be difficult to establish, particularly where urbanization has occurred within the gauged watershed, altering the response of the affected watershed to precipitation. This alteration can produce a nonstationary streamflow signal that can be significant, depending on the percentage of the watershed altered. As urbanization increases, peak discharges are shown to increase, producing a positive trend in the annual maximum series. Urbanization occurring during and/or after the gauging period is quantified using spatially and temporally distributed land use data. Three statistical tests ͑a parametric t-test on the slope of the linear relationship between the flood series and time and two nonparametric tests: the Kendall's Tau and the Spearman Rank Correlation͒ are performed on both the annual maximum discharge and annual maximum discharge-precipitation ratios series to test for trends or nonstationary signals corresponding to periods of urbanization. A case study suggests that the ratios are more effective than the discharges alone for identifying nonstationarity resulting from urbanization. In addition, relationships between measures of urbanization and the presence or absence of significant trends in the discharge series are presented.
Hydrologic similarity of river basins through regime stability
The seasonality of streamflow can vary widely from river to river and is influenced mostly by the local seasonal cycles of precipitation and evaporation demand, by the timing of snowmelt (if any), as well as by travel times of the groundwater component of runoff.
Streamflow Response of an Agricultural Watershed to Seasonal Changes in Precipitation
2000
Seasonal variations in precipitation on a watershed lead to variations in streamflow that in turn result in uncertainties that impede the efficient management of available water resources. This is especially true for management of reservoir storage and water releases during and at the end of the dry season when water demand is highest and streamflow supply is lowest. Anticipating streamflow
Characterization of watershed model behavior across a hydroclimatic gradient
Water Resources Research, 2008
1] A fundamental tradeoff exists in watershed modeling between a model's flexibility for representing watersheds with different characteristics versus its potential for overparameterization. This study uses global sensitivity analysis to investigate how a commonly used intermediate-complexity model, the Sacramento Soil Moisture Accounting Model (SAC-SMA), represents a wide range of watersheds with diverse physical and hydroclimatic characteristics. The analysis aims to establish a detailed understanding of model behavior across watersheds and time periods with the ultimate objective to guide model calibration and evaluation studies. Sobol's sensitivity analysis is used to evaluate the SAC-SMA in 12 Model Parameter Estimation Experiment (MOPEX) watersheds in the US. The watersheds span a wide hydroclimatic gradient from arid to humid systems. Four evaluation metrics reflecting base flows, midrange flows, peak flows, and long-term water balance were used to comprehensively characterize trends in sensitivity and model behavior. Results show significant variation in parameter sensitivities that are correlated with the hydroclimatic characteristics of the watersheds and time periods analyzed. The sensitivity patterns are consistent with the expected dominant processes and demonstrate the need for moderate model complexity to represent different hydroclimatic regimes. The analysis reveals that the primary model controls for some aspects of the simulated hydrograph are different from those typically assumed for the SAC-SMA. Results also show that between 6 and 10 parameters are regularly identifiable from daily hydrologic data, which is about twice the range that is often assumed (i.e., 3 to 5). Synthesized results provide comprehensive SAC-SMA calibration guidance, demonstrate the flexibility of the model for representing multiple hydroclimatic regimes, and highlight the great difficulty in generalizing model behavior across watersheds.
Nonstationarity versus scaling in hydrology
Journal of Hydrology, 2006
The perception of a changing climate, which impacts also hydrological processes, is now generally admitted. However, the way of handling the changing nature of climate in hydrologic practice and especially in hydrological statistics has not become clear so far. The most common modelling approach is to assume that long-term trends, which have been found to be omnipresent in long hydrological time series, are "deterministic" components of the time series and the processes represented by the time series are nonstationary. In this paper, it is maintained that this approach is contradictory in its rationale and even in the terminology it uses. As a result, it may imply misleading perception of phenomena and estimate of uncertainty. Besides, it is maintained that a stochastic approach hypothesizing stationarity and simultaneously admitting a scaling behaviour reproduces climatic trends (considering them as large-scale fluctuations) in a manner that is logically consistent, easy to apply and free of paradoxical results about uncertainty.
A practicable approach for evaluating runoff changes in ungauged basins
In hydrology a basic task is the estimation of design discharges and runoff changes in ungauged catchments. However, traditional empirical rules of thumb as well as regionalization of measured discharges are subject to uncertainty. It seems that precipitation-runoff modelling is the only comprehensible way to predict discharge alterations due to changes in ungauged basins, even though the results are perhaps not less uncertain. In order to minimize this uncertainty we supplemented a methodology for discharge estimation in ungauged basins by introducing runoff coefficients derived from field assessment, an adapted precipitation-runoff model (ZEMOKOST) and routines for a plausibility check. Subsequently ten gauged Austrian catchments were used as hypothetical ungauged catchments for application and verification of this method. Except for special questions in karst- and glacier-hydrology the procedure showed satisfying results. In addition, the approach has been tested in catchments that have been intensively impacted by human use in the last decades; in this regard variations in discharge and future runoff characteristics have been analyzed.
The Effect of Climate Change on Watershed Water Balance
Mathematical Advances Towards Sustainable Environmental Systems, 2016
Climate change refers to a statistically significant long-term shift in the pattern (mean state and variability) of regional or global climate. This phenomenon is attributed to human activities, which have resulted in an increased concentration of greenhouse gases in the global atmosphere. Climate change is already having major effects on the physical environment and biota. The highlighted study investigated the effects of climate change on the sustainability of water resources at a watershed scale, by defining different patterns of climate change (i.e. ideal, medium, and critical) and weighing the output of different general circulation models (GCM). Based on given climate change patterns, the meteorological data (particularly near and far future temperature and precipitation data) were downscaled to the local or regional scale using stochastic weather generators (WGs). The link between climate change and surface runoff was then developed by modelling unit hydrographs within the conceptual framework of rainfall-runoff models. This allowed a reasonable estimate of the future state of surface water resources in the face of climate change to be made; as well as an assertion of the impact of climate change on intra-watershed water consumption (e.g. agricultural, industrial, domestic). Water resource sustainability indices were used to assess the impact of climate change on water resource dynamics within watersheds.
Hydrological Processes, 2013
Thanks to its simple division into agricultural and forestry land use, the Corbeira catchment (Galicia, Spain) is used as a case study to build a predictive model using hydrogeochemical signatures. Stream data acquired under recessional flow conditions over a one year period were obtained from a sampling station near the downstream end of the catchment, and using principal component analysis, it is shown that some of the analytical parameters are covariant, and some are negatively correlated. These findings support inferences about the pathways of rainfall in the catchment. Specific signatures may be associated with the dominant hydrological source, either surface runoff or subsurface waters: additionally, the dominant land use in that part of the catchment, where the flow originated, can also be predicted. The dominant runoff shows a strong covariance between suspended solids (SS) and particulate phosphorus (PP), with a clear negative correlation with pH. Dissolved organic carbon (DOC) data are associated with this covariant set when these compounds are available in the soils in question. Dissolved phosphorus, total organic nitrogen and dissolved nitrates are also associated with the same covariant set when the runoff flows through areas of extensive agricultural use. The SS À PP covariance is less significant at lower flows. Typical base flow regimes show a significant covariance between salinity and pH, with a marked negative correlation with SS À PP set, confirming the dominance of subsurface waters in the baseflow, as expected. Seasonally divergent DOC À SS behaviour proves to be a useful tracer for rainfall regimes. The DOC trend shows a sinusoidal annual variation in amplitude, determined by the rainfall regime. As a result, flow from the catchment is dominated by surface water whenever there is synchronicity between the peaks of DOC and SS.
Robust parametric models of runoff characteristics at the mesoscale
Journal of Hydrology, 2005
Many hydrologic studies report that runoff characteristics such as means or extremes of a given basin may be modified due to climatic and/or land use/cover changes and that the magnitude of these changes largely depends on the geographic location and the scale at which the study is carried out. Identifying the main causes of variability at the mesoscale, however, is a challenging task because of the lack of data regarding the spatial distribution of relevant explanatory variables and, if they exist, because of their high uncertainty. This study proposes a general method to find a robust non-linear model by solving a constrained multiobjective optimization problem whose solution space is composed of all feasible combinations of given explanatory variables. As a result, a model that simultaneously fulfills several criteria such as parsimony, robustness, significance, and overall performance is expected. Furthermore, it does not require assumptions regarding the sampling distributions neither of the parameters nor of the estimators because their p-values are estimated by a non-parametric technique. Finally, there is no limitation with respect to the functional form adopted for a given model and its estimator because a generalized reduced gradient algorithm is used for the calibration of its parameters. The proposed method was tested in the upper catchment of the Neckar River (Germany) covering an area of approximately 4000 km 2 . The objective of this study was to detect trends and responses of runoff characteristics in mesoscale catchments due to changes of climatic or land use/cover conditions. In this case, the explained variables are the specific total discharge in summer and winter whereas the explanatory variables comprise several physiographic, land cover and climatic characteristics evaluated for 46 subcatchments during the period 1961-1993. The results of the study indicate a significant gain in performance and robustness of the selected models compared to traditional stepwise methods. The applicability of this method to other disciplines and/or locations is possible. q