Conceptual Rainfall-runoff Model Research Articles

A new framework for comprehensive, robust, and efficient global sensitivity analysis: 2. Application

AbstractBased on the theoretical framework for sensitivity analysis called “Variogram Analysis of Response Surfaces” (VARS), developed in the companion paper, we develop and implement a practical “star‐based” sampling strategy (called STAR‐VARS), for the application of VARS to real‐world problems. We also develop a bootstrap approach to provide confidence level estimates for the VARS sensitivity metrics and to evaluate the reliability of inferred factor rankings. The effectiveness, efficiency, and robustness of STAR‐VARS are demonstrated via two real‐data hydrological case studies (a 5‐parameter conceptual rainfall‐runoff model and a 45‐parameter land surface scheme hydrology model), and a comparison with the “derivative‐based” Morris and “variance‐based” Sobol approaches are provided. Our results show that STAR‐VARS provides reliable and stable assessments of “global” sensitivity across the full range of scales in the factor space, while being 1–2 orders of magnitude more efficient than the Morris or Sobol approaches.

The impact of the variability and periodicity of rainfall on surface water supply systems in Scotland

This paper analyses the impact of the variability and periodicity of rainfall on the reliability of water supply systems in Scotland. A conceptual rainfall-runoff model was used to simulate catchment runoff, and the reliability of 29 notional and six actual reservoirs was calculated using a simple storage model. The relationship between water supply reliability and the variability of rainfall was then investigated using different measures of variability. A strong correlation was found between reservoir reliability and measures representing the distribution of rainfall between the winter and summer seasons, as well as the cumulative sum (CUSUM) of annual precipitation, quantifying the variability of rainfall between years. In contrast, mainly the intra-annual CUSUM range and the variance of monthly precipitation influenced the reliability of river-intake schemes. The presence of periodic patterns in rainfall anomalies was found to be more prevalent in West Scotland, where reservoir reliability is on average lower than in the East. In addition, a sensitivity analysis revealed the small influence of evapotranspiration on reservoir reliability in comparison to rainfall variability. This study reveals the measures of variability most affecting the reliability of surface water supplies in Scotland, and could therefore help with their management in the context of future climate change.

Feasibility and uncertainty of using conceptual rainfall-runoff models in design flood estimation

Hydrological models are developed for different purposes including flood forecasting, design flood estimation, water resources assessment, and impact study of climate change and land use change, etc. In this study, applicability and uncertainty of two deterministic lumped models, the Xinanjiang (XAJ) model and the Hydrologiska Byråns Vattenbalansavdelning (HBV) model, in design flood estimation are evaluated in a data rich catchment in southern China. Uncertainties of the estimated design flood caused by model equifinality and calibration data period are then assessed using the generalized likelihood uncertainty estimation (GLUE) framework. The results show that: (1) the XAJ model is likely to overestimate the design flood while HBV model underestimates the design flood; (2) the model parameter equifinality has significant impact on the design flood estimation results; (3) with the same length of calibration period, the results of design flood estimation are significantly influenced by which period of the data is used for model calibration; and (4) 15–20 years of calibration data are suggested to be necessary and sufficient for calibrating the two models in the study area.

Coupled modeling approach to assess climate change impacts on groundwater recharge and adaptation in arid areas

Abstract. The effect of future climate scenarios on surface and groundwater resources was simulated using a modeling approach for an artificial recharge area in arid southern Iran. Future climate data for the periods of 2010–2030 and 2030–2050 were acquired from the Canadian Global Coupled Model (CGCM 3.1) for scenarios A1B, A2, and B1. These scenarios were adapted to the studied region using the delta-change method. A conceptual rainfall–runoff model (Qbox) was used to simulate runoff in a flash flood prone catchment. The model was calibrated and validated for the period 2002–2011 using daily discharge data. The projected climate variables were used to simulate future runoff. The rainfall–runoff model was then coupled to a calibrated groundwater flow and recharge model (MODFLOW) to simulate future recharge and groundwater hydraulic heads. As a result of the rainfall–runoff modeling, under the B1 scenario the number of floods is projected to slightly increase in the area. This in turn calls for proper management, as this is the only source of fresh water supply in the studied region. The results of the groundwater recharge modeling showed no significant difference between present and future recharge for all scenarios. Owing to that, four abstraction and recharge scenarios were assumed to simulate the groundwater level and recharge amount in the studied aquifer. The results showed that the abstraction scenarios have the most substantial effect on the groundwater level and the continuation of current pumping rate would lead to a groundwater decline by 18 m up to 2050.

Evolution of a parsimonious rainfall–runoff model using soil moisture proxies

Pre-storm soil moisture conditions play a crucial role in the analysis of the physical processes involved in conceptual rainfall–runoff modeling and for demonstration of the soil–water–atmosphere interaction. Runoff quantification is of common interest to most hydrologists who study rainfall–runoff modeling. The scientific community prefers hydrological models with a smaller number of parameter requirements and superior performance, because of the increased water resource applications. In order to circumvent the impacts of sudden undesirable jumps (e.g., in the conventional CN model) in runoff estimation, we investigated the integral effects of soil moisture proxies before and after rainfall occurrence so as to reduce the structural inconsistencies of the previous models. Accordingly, these sudden jumps were avoided by incorporating a new expression that varied from storm to storm and with prior rainfall. Similarly, the utilization of additional information to calibrate new parameters reduced the applicability to ungauged watersheds. By persisting with the principle of simplicity and avoiding over-parameterization, a new model was developed and validated using measured data of 1804 storm rainfall–runoff events from 39 South Korean watersheds. The significant results exhibited by the suggested one-parameter model in comparison to those of the other contenders were hydrologically justified using three statistical metrics and scatter plots.

Analytical Derivation of Overland Travel Time Based on Diffusive Wave Solution

AbstractDerivation of spatial distribution of travel time is required in some conceptual rainfall-runoff transformation models. Application of a kinematic wave (KW) solution to delineate isochrones of travel time may be straightforward, particularly in an overland flow regime. In this article, a new analytical approach based on the diffusive wave (DW) solution is developed for calculation of travel time. The discharge hydrograph over a rectangular plane will be calculated based on the developed analytical DW method through the application of the time-area method. Differences between calculated maximum travel time (i.e., equilibrium time), isochrone locations, and outflow discharge between the KW and DW solutions are compared with those of the numerical dynamic wave (DYW) solution. It is shown that analytical DW results are closer to those of the DYW in comparison with those of the KW. The effect of the K0F02 number on the solution accuracy is investigated, where K0 is the kinematic wave number and F0 is t...

Application of a modified conceptual rainfall–runoff model to simulation of groundwater level in an undefined watershed

Groundwater level simulation models can help ensure the proper management and use of urban and rural water supply. In this paper, we propose a groundwater level tank model (GLTM) based on a conceptual rainfall–runoff model (tank model) to simulate fluctuations in groundwater level. The variables used in the simulations consist of daily rainfall and daily groundwater level, which were recorded between April 2011 and March 2015 at two representative observation wells in Kumamoto City, Japan. We determined the best-fit model parameters by root-mean-square error through use of the Shuffled Complex Evolution-University of Arizona algorithm on a simulated data set. Calibration and validation results were evaluated by their coefficients of determination, Nash–Sutcliffe efficiency coefficients, and root-mean-square error values. The GLTM provided accurate results in both the calibration and validation of fluctuations in groundwater level. The split sample test results indicate a good reliability. These results indicate that this model can provide a simple approach to the accurate simulation of groundwater levels.

Estimation of the impact of climate change-induced extreme precipitation events on floods

Abstract In order to estimate possible changes in the flood regime in the mountainous regions of Slovakia, a simple physically-based concept for climate change-induced changes in extreme 5-day precipitation totals is proposed in the paper. It utilizes regionally downscaled scenarios of the long-term monthly means of the air temperature, specific air humidity and precipitation projected for Central Slovakia by two regional (RCM) and two global circulation models (GCM). A simplified physically-based model for the calculation of short-term precipitation totals over the course of changing air temperatures, which is used to drive a conceptual rainfall-runoff model, was proposed. In the paper a case study of this approach in the upper Hron river basin in Central Slovakia is presented. From the 1981–2010 period, 20 events of the basin’s most extreme average of 5-day precipitation totals were selected. Only events with continual precipitation during 5 days were considered. These 5-day precipitation totals were modified according to the RCM and GCM-based scenarios for the future time horizons of 2025, 2050 and 2075. For modelling runoff under changed 5-day precipitation totals, a conceptual rainfall-runoff model developed at the Slovak University of Technology was used. Changes in extreme mean daily discharges due to climate change were compared with the original flood events and discussed.

토양저류함수 모형을 이용한 개념적 강우 유출모형의 장기 유출 모의 적용성 평가

금강유역의 특성인자 기반의 유역그룹과 토양저류함수모형기반의 개념적 강우유출모형의 적용관계를 평가하였다. 3개의 유역 그룹은 금강 22개 계측 유역의 주요 유역특성인자(면적, 경사도, SCS-CN)의 수문학적 거리산정방법으로 산정하였다. 개념적 강우유출모형은 3개의 토양저류 함수 모형(확률분포모형(PDM), 유역습윤지수 모형(CWI), 수정팬맨 모형(MP))과 3개의 개념적 유역유출모형(2선형저류지 유출 모형(2PAR), 표면하 흐름을 고려한 2선형저류지 모형(2PMP), 3선형저류지 모형(3PAR)의 조합형으로 9개의 모형을 적용하였다. 대상 모형은 2006년~2012년의 기간, 2001-2005년의 기간의 일자료를 대상으로 각각 검정(Monte Carlo method-Uniform Random Sampling) 및 검증을 수행하였다. 모형의 성능은 Nash Sutcliffe Efficiency 목적함수로 평가하였다. 금강의 유역그룹과 토양 저류함수모형의 모형성능과의 뚜렷한 상관성을 확인할 수 없다. 따라서 금강유역을 단일 유역그룹으로 적용할 수 있음을 제시하였다. 검정/검증 성능 및 검정매개변수의 개수를 바탕으로 한 적용성 평가 결과에서 확률분포모형(PDM)이 금강 22개 유역에 대하여 전반적으로 적용성이 우수함을 확인하였다. 따라서 확률분포모형(PDM)과 2선형 저류지 유출 모형(2PAR)을 금강 강우유출모형개발을 위한 기본모형으로 제시하고, 향후 이를 바탕으로 금강유역의 바탕으로 금강유역의 대표 강우유출모형을 개발 하고자 한다. This study assesses a relationship between catchment groups and model performance of nine Conceptual Rainfall Runoff models at 22 Guem river sub catchments. Three catchment groups (H1, H2 and H3) are derived from Hydrological distance measuring based on three catchment characteristics (i.e. Area, slope and SCS-CN). 9 CRR models, which are combined from 3 Soil Moisture Accounting models (Probability Distributed Model, Catchment Wetness Index model, Modified Penman type model) and 3 Routing models (2-conceptual reservoirs in parallel, 2-conceptual reservoirs in parallel with Macro-pre Approach, 3-conceptual reservoirs in parallel) in Rainfall-Runoff Modeling Toolkit. The models are calibrated and validated in the period of 2006-2012 and 2001-2005 respectively. The model performance in Nash Surcliffe Efficiency is compared in terms of model structures and catchment groups. The results show that there is no significant relationship between catchment groups and model structures and suggest one group for Guem river region. However, PDM-SMA Models show generally good performances in calibration, validation and Number of calibrated model parameters. PDM with 2PAR model is recommended as a rainfall runoff model for Guem river region.

Hydrological modelling under climate change considering nonstationarity and seasonal effects

Traditional hydrological modelling assumes that the catchment does not change with time. However, due to changes of climate and catchment conditions, this stationarity assumption may not be valid in the future. It is a challenge to make the hydrological model adaptive to the future climate and catchment conditions. In this study IHACRES, a conceptual rainfall–runoff model, is applied to a catchment in southwest England. Long observation data (1961–2008) are used and seasonal calibration (only the summer) has been done since there are significant seasonal rainfall patterns. Initially, the calibration is based on changing the model parameters with time by adapting the parameters using the step forward and backward selection schemes. However, in the validation, both models do not work well. The problem is that the regression with time is not reliable since the trend may not be in a monotonic linear relationship with time. Therefore, a new scheme is explored. Only one parameter is selected for adjustment while the other parameters are set as the fixed and the regression of one optimised parameter is made not only against time but climate condition. The result shows that this nonstationary model works well both in the calibration and validation periods.

Hydrological Simulation of the Upper Hirmand Transboundary Catchment Using SWAT Model

One of the major challenges in water resources management is the operation of trans boundary watershed. This has been experienced in case of Helmand River between Iran and Afghanistan since the last century. For such a situation, application of a conceptual rainfall-runoff models that can simulate management scenarios is a relevant tool. The SWAT model can be a relevant option in this regard. However, the required hydro-climatic data for them is a serious obstacle. Especially, this problem gets exacerbated in the case of Afghanistan with poor infrastructures. So, application of this type of model would be more problematic. This paper aims to investigate capabilities of SWAT for the simulation of rainfall-runoff processes in such a data-scarce region and the upper catchment of Helmand River is used as the case study. For this purpose, discharge data of Dehraut station from 1969 to 1979 along with some metrological data were prepared and used to calibrate and validate the simulations. The results were acceptable and the coefficients of determinations (R) during calibration and validation periods were 0.76 and 0.70, respectively. Notably, with respect to snowy condition of the basin, the elevation band option of the snow module of model had a significant effect on the results, especially in the base flows. Moreover, two Landsat satellite images during February 1973 and 1977 when the basin was partly covered with snow was prepared and compared with the SWAT outputs. Similarly, the results showed good performance of the model such that R were 0.87 and 0.82, respectively.

Advancing tracer‐aided rainfall–runoff modelling: a review of progress, problems and unrealised potential

AbstractUsing conservative tracers to aid conceptual rainfall–runoff modelling has gained momentum over the past decade. Tracer data have been invaluable in providing rich insights into runoff sources, flow paths and water age that cannot be established by simple rainfall–runoff dynamics alone. Accordingly, this has provided a focus for fertile dialogue between field hydrologists and modellers in joint efforts to understand catchment function and incorporate this in runoff models. Central to this has been the utility of tracers in establishing the differences between the timescales of the celerity of the rainfall–runoff response and the timescales of the pore velocity of water. The literature now has numerous examples of using tracers to aid modelling as a learning framework. Despite this progress, utilization of tracer‐aided models and exploitation of their evident advantages by the wider modelling community have been slow. This in part reflects lack of suitable data sets at many sites and the fact that studies to date have highlighted various problems and challenges when trying to integrate tracers into rainfall–runoff models (e.g. increased parameterisation). Nevertheless, interest in tracer‐aided modelling has continued to build as there have been marked improvements in the reliability and economics of field and laboratory methods for collecting spatially distributed and high temporal resolution tracer data sets. Consequently, we stand on the threshold of unprecedented advances in applications of this area. Here, we critically evaluate the progress to date and assess the challenges that remain. The key current research frontiers with the greatest potential for rapid advancement are as follows: (1) to go beyond hydrograph simulation alone and build more realistic models of catchment functioning based on tracer data, (2) investigations into the nonlinear, threshold‐type, non‐stationary and hysteresis‐driven nature of how catchments process water and solutes, (3) detailed eco‐hydrological studies of connectivity patterns and the role of vegetation on water partitioning and (4) the assessment of anthropogenic influences on the catchment hydrological cycle. Copyright © 2015 John Wiley & Sons, Ltd.

State estimation in flash flood prediction for small rivers

Abstract Rainfall–runoff models are used as an integral part of flood warning systems. Especially in small river catchment areas with a fast response to intense rain, an early enough triggering of warnings requires high quality weather forecasts as well as sufficiently accurate models. A conceptual rainfall–runoff model proposed by Lorent/Gevers serves as core routine of a pilot flash flood warning system for the Truse catchment in Thuringia (Germany). A moving horizon state estimator is used in order to enable this model for online application.

A simple hydrologic model for rapid prediction of runoff from ungauged coastal catchments

We developed a lumped conceptual rainfall–runoff model for rapid prediction of runoff generated in the unique hydrological setting with flat terrain, sandy soils, high groundwater table, and a dense drainage canal network in south Florida. The model is conceptualized as rainfall and evapotranspiration filling and emptying the root zone and excess rainfall recharging three storage zones. Outflows from these storage zones, routed with parallel arrangement of three linear reservoirs, represent different flow components of catchment runoff, i.e., slow drainage (shallow subsurface flow), medium drainage (interflow and saturation excess overland flow), and fast drainage (direct runoff from impervious urban areas or from water table management in agricultural land). The model is parsimonious with eight model parameters along with two optional water management parameters. A regionalization study was conducted through model parameterization to achieve target hydrological behavior of typical land uses, which are the most significant basin descriptor affecting catchment hydrology in south Florida. Cross validation with 16 gauged basins dominated by urban, agricultural, and natural lands, respectively, indicated that the model provides an effective tool for rapid prediction of runoff in ungauged basins using the regionalized model parameters. A case study is presented, involving application of the model to support real-time adaptive management to hydrological operations for protection of estuarine ecosystems.

Groundwater balance estimation in karst by using simple conceptual rainfall–runoff model

The objective of this work is the study of Opacac karst spring which geographically lies in Dalmatia (Croatia). Numerous studies have been carried out in karst aiming the investigation of groundwater regime. The karst spring hydrograph can reflect the groundwater regime and consequently the analysis is based on them. A simple conceptual rainfall–runoff model is used for the estimation of groundwater balance components including the influences of time-invariant catchment boundaries (Jukic and Denic-Jukic 2009). The proposed parameter estimation procedure merges the soil-moisture balance and the groundwater balance approaches to obtain the complete groundwater budget. The effective rainfall is calculated by using mathematical model based on soil-moisture balance equations, i.e. Palmer’s fluid mass balance method. The parameters of model of effective rainfall are determined by using simple conceptual rainfall–runoff model consisting of two linear reservoirs representing the fast and slow flow component of the recession. The weight coefficient between the fast and slow component is determined by using base flow index analysis of hydrograph. Recession coefficient of the slow flow component and the weight coefficient are determined from hydrograph analysis. Available data from nearby meteorological station includes daily average discharge, the amount of precipitation, the average temperature and the humidity from 1995 to 2010. The average catchment area is also estimated with the average yearly runoff deficit using Turc’s method and compared with the values obtained from the application of the rainfall–runoff model. Nash–Sutcliffe model efficiency, root mean square error and Pearson’s correlation coefficient for simulated hydrograph are applied to assess the predictive power of model. Calculated groundwater balance shows that the Opacac spring aquifer contains a significant storage capacity. The application of series of linear reservoirs is a classical and common technique, but the proposed simple approach enables the estimation of the components of groundwater balance in karst areas.

Conceptual rainfall-runoff model with a two-parameter, infinite characteristic time transfer function

A two-parameter transfer function with an infinite characteristic time is proposed for conceptual rainfall-runoff models. The large time behaviour of the unit response is an inverse power function of time. The infinite characteristic time allows long term memory effects to be accounted for. Such effects are observed in mountainous and karst catchments. The governing equation of the model is a fractional differential equation in the limit of long times. Although linear, the proposed transfer function yields discharge signals that can usually be obtained only using non-linear models. The model is applied successfully to two catchments, the Dud Koshi mountainous catchment in the Himalayas and the Durzon karst catchment in France. It compares favourably to the linear, non-linear single reservoir models and to the GR4J model. With a single reservoir and a single transfer function, the model is capable of reproducing hysteretic behaviours identied as typical of long term memory effects. Computational efficiency is enhanced by approximating the infinite characteristic time transfer function with a sum of simpler, exponential transfer functions. This amounts to partitioning the reservoir into several linear subreservoirs, the output discharges of which are easy to compute. An efficient partitioning strategy is presented to facilitate the practical implementation of the model.

Non-stationarity driven by long-term change in catchment storage: possibilities and implications

Abstract. "Non-stationarity" with reference to hydrology is a term applied to many situations (Milly et al., 2008). While climate change non-stationarity is often examined, these effects can provide a test for assumptions of runoff generation process impliedin rainfall–runoff (RR) models. Observations from South-western Australia (SWA) over the past 40 years show a decline in rainfall and reductions in runoff. Runoff and rainfall relationships in SWA show a significant shift over the past 40 years suggesting a change in runoff generation and catchment state. This has challenged the nature of assumed runoff generation process in SWA as well as the veracity of conceptual RR model structure. We expand on some of the lessons learned from SWA and discuss the climatic and geomorphic conditions that may make reasonable predictions of runoff very difficult with RR models calibrated in traditional ways. Catchment storage has a significant interaction with runoff generation and we examine the situations where these may change in the longer term. We suggest some strategies in terms of model structure and calibration that may improve predictive performance in such situations.

Changes in the snow water equivalent in mountainous basins in Slovakia over recent decades

Abstract. Changes in snowpack and duration of snow cover can cause changes in the regime of snow and rain-snow induced floods. The recent IPCC report suggests that, in snow-dominated regions such as the Alps, the Carpathian Mountains and the northern parts of Europe, spring snowmelt floods may occur earlier in a future climate because of warmer winters, and flood hazards may increase during wetter and warmer winters, with more frequent rain and less frequent snowfall. The monitoring and modelling of snow accumulation and snow melting in mountainous catchments is rather complicated, especially due to the high spatial variability of snow characteristics and the limited availability of terrestrial hydrological data. An evaluation of changes in the snow water equivalent (SWE) during the period of 1961–2010 in the Upper Hron river basin, which is representative of the mountainous regions in Central Slovakia, is provided in this paper. An analysis of the snow cover was performed using simulated values of the snow water equivalent by a conceptual semi-distributed hydrological rainfall-runoff model. Due to the poor availability of the measured snow water equivalent data, the analysis was performed using its simulated values. Modelling of the SWE was performed in different altitude zones by a conceptual semi-distributed hydrological rainfall-runoff model. The evaluation of the results over the past five decades indicates a decrease in the simulated snow water equivalent and the snow duration in each altitude zone and in all months of the winter season. Significant decreasing trends were found for December, January and February, especially in the highest altitude zone.

Fuzzy Logic for Rainfall-Runoff Modelling Considering Soil Moisture

This study developed Mamdani-type fuzzy logic model to simulate daily discharge as a function of soil moisture measured at three different depths (10, 20 and 40 cm) and rainfall. The model was applied to 13 km2 size Colorso Basin in central Italy for a period from October 2002 to April 2004. For each variable of soil moisture, rainfall, and discharge, 9 fuzzy subsets were employed while 30 fuzzy rules, relating the input variables (soil moisture and rainfall) to the output variable (discharge), were optimized. The model employed the min inferencing, max composition, and the centroid method. The model application results revealed that Mamdani-type fuzzy logic model can be employed to incorporate soil moisture along with rainfall to simulate discharge. Using soil moisture measured at 40 cm soil depth along with rainfall produced better simulation of discharge with NS = 0.68 and R = 0.82. The performance of the model was also tested against a conceptual rainfall-runoff model of MISDc (Modello Idrologico Semi-Distribuito in continuo). MISDc couples an event-specific component with a module for continuous time soil water balance for taking into account the variable antecedent wetness conditions. The MISDc model requires estimation of seven parameters and the measurements of the hydrometeorological variables such as rainfall and air temperature. The comparative study revealed that fuzzy model performs better in capturing runoff peak rates and overall trend of high and small flooding events.

Evaluation of the HYMOD model for rainfall–runoff simulation using the GLUE method

Abstract. The Yalong River is the third largest base of the 13 hydropower bases in China. Long-time series of river discharge records are essential for the design of hydropower stations and water resource management. The existing monitoring network is scarce and cannot provide sufficient hydrological information for the basin. Rainfall–runoff models are popular tools for extending hydrological data in both space and time. In this paper, the feasibility of applying a conceptual rainfall–runoff model, HYdrological MODel (HYMOD), to the upper Yalong River basin was evaluated. The generalized likelihood uncertainty estimation (GLUE) was employed for model calibration and uncertainty analysis. The results show that simulated discharge matches the observations satisfactorily, indicating the hydrological model performs well and the application of HYMOD to estimate long time-series of river discharge in the study area is feasible.