Using a parsimonious rainfall–runoff 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.

Assessment of the Analytic and Hydrologic Methods in Separation of Watershed Responses to Climate and Land Use Changes

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.

Analysis of the Relative Importance of Model Parameters in Watersheds with Different Hydrological Regimes

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.