Sensitivity of hydrological variables to climate change in the Haihe River basin,China

Using the defined sensitivity index, the sensitivity of streamflow, evapotranspiration and soil moisture to climate change was investigated in four catchments in the Haihe River basin. Climate change contained three parts: annual precipitation and temperature change and the change of the percentage of precipitation in the flood season (P_f). With satisfying monthly streamflow simulation using the variable infiltration capacity model, the sensitivity was estimated by the change of simulated hydrological variables with hypothetical climatic scenarios and observed climatic data. The results indicated that (i) the sensitivity of streamflow would increase as precipitation or P_f increased but would decrease as temperature increased; (ii) the sensitivity of evapotranspiration and soil moisture would decrease as precipitation or temperature increased, but it to P_f varied in different catchments; and (iii) hydrological variables were more sensitive to precipitation, followed by P_f, and then temperature. The nonlinear response of streamflow, evapotranspiration and soil moisture to climate change could provide a reference for water resources planning and management under future climate change scenarios in the Haihe River basin. Copyright © 2011 John Wiley & Sons, Ltd.     

Global sensitivity analyses for a complex hydrological model applied in an Alpine watershed

The increasing complexity of hydrological models results in a large number of parameters to be estimated. In order to better understand how these complex models work, efficient screening methods are required in order to identify the most important parameters. This is of particular importance for models that are used within an operational real‐time forecasting chain such as HQsim. The objectives of this investigation are to (i) identify the most sensitive parameters of the complex HQsim model applied in the Alpine Lech catchment and (ii) compare model parameter sensitivity rankings attained from three global sensitivity analysis techniques. The techniques presented are the (i) regional sensitivity analysis, (ii) Morris analysis and (iii) state‐dependent parameter modelling. The results indicate that parameters affecting snow melt as well as processes in the unsaturated soil zone reveal high significance in the analysed catchment. The snow melt parameters show clear temporal patterns in the sensitivity whereas most of the parameters affecting processes in the unsaturated soil zone do not vary in importance across the year. Overall, the maximum degree day factor (meltfunc_max) has been identified to play a key role within the HQsim model. Although the parameter sensitivity rankings are equivalent between methods for a number of parameters, for several key parameters differing results were obtained. An uncertainty analysis demonstrates that a parameter ranking attained from only one method is subjected to large uncertainty. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessment of surface water resources and evapotranspiration in the Haihe River basin of China using SWAT model

Quantitative assessment of surface water resources (SWRs) and evapotranspiration (ET) is essential and significant for reasonably planning and managing water resources in the Haihe River basin which is facing severe water shortage. In this study, a distributed hydrological model of the Haihe River basin was constructed using the Soil and Water Assessment Tool, well considering the reservoirs and agricultural management practices for reasonable simulation. The crop parameters were independently calibrated with the observed crop data at six experimental stations. Then, sensitivity ranks of hydrological parameters were analysed, which suggested the important parameters used for calibration. The model was successfully calibrated using the monthly observed data of discharge in around 1970–1991 and actual ET (ET_a) in 2002–2004 for the mountainous area and Haihe plain, respectively. Meanwhile, good agreements between the simulated and statistical crop yields in 1985–2005 further verified the model's appropriateness. Finally, the calibrated model was used to assess SWRs and ET_a in time and space during 1961–2005. Results showed that the average annual natural SWRs and the ET_a were about 17.5 billion cubic metre and 542 mm, respectively, both with a slight downward trend. The spatial distributions of both SWRs and ET_a were significantly impacted by variations of precipitation and land use. Moreover, the reservoir in operation was the main factor for the noticeable decline of actual SWRs. In the Haihe plain, the ET_a with irrigation was increased by 46% compared with that under rainfed conditions. In addition, this study identified the regions with potential to improve the irrigation effects on water use. Copyright © 2012 John Wiley & Sons, Ltd.     

Impact of climate change on hydrological processes over a basin scale in northern Taiwan

This study investigates the impact of climate change on rainfall, evapotranspiration, and discharge in northern Taiwan. The upstream catchment of the Shihmen reservoir in northern Taiwan was chosen as the study area. Both observed discharge and soil moisture were simultaneously adopted to optimize the HBV‐based hydrological model, clearly improving the simulation of the soil moisture. The delta change of monthly temperature and precipitation from the grid cell of GCMs (General Circulation Models) that is closest to the study area were utilized to generate the daily rainfall and temperature series based on a weather generating model. The daily rainfall and temperature series were further inputted into the calibrated hydrological model to project the hydrological variables. The studies show that rainfall and discharge will be increased during the wet season (May to October) and decreased during the dry season (November to April of the following year). Evapotranspiration will be increased in the whole year except in November and December. Copyright © 2009 John Wiley & Sons, Ltd.     

Effects of land‐use changes on hydrological processes in the middle basin of the Heihe River,northwest China

The effects of land‐use changes on the runoff process in the midstream plain of this arid inland river basin are a key factor in the rational allocation of water resources to the middle and lower reaches. The question is whether and by how much increasingly heavy land use impacts the hydrological processes in such an arid inland river basin. The catchment of the Heihe River, one of the largest inland rivers in the arid region of northwest China, was chosen to investigate the hydrological responses to land‐use change. Flow duration curves were used to detect trends and variations in runoff between the upper and lower reaches. Relationships among precipitation, upstream runoff, and hydrological variables were identified to distinguish the effects of climatic changes and upstream runoff changes on middle and downstream runoff processes. The quantitative relation between midstream cultivated land use and various parameters of downstream runoff processes were analysed using the four periods of land‐use data since 1956. The Volterra numerical function relation of the hydrological non‐linear system response was utilized to develop a multifactor hydrological response simulation model based on the three factors of precipitation, upstream runoff, and cultivated land area. The results showed that, since 1967, the medium‐ and high‐coverage natural grassland area in the midstream region has decreased by 80·1%, and the downstream runoff has declined by 27·32% due to the continuous expansion of the cultivated land area. The contribution of cultivated land expansion to the impact on the annual total runoff is 14–31%, on the annual, spring and winter base flow it is 44–75%, and on spring and winter discharge it is 23–64%. Once the water conservation plan dominated by land‐use structural adjustments is implemented over the next 5 years, the mean annual discharge in the lower reach could increase by 8·98% and the spring discharge by 26·28%. This will significantly alleviate the imbalance between water supply and demand in both its quantity and temporal distribution in the middle and lower reaches. Copyright © 2006 John Wiley & Sons, Ltd.     

Responses of hydrological processes to climate change in the Yarlung Zangbo River basin

ABSTRACT

Climate change alters hydrological processes and results in more extreme hydrological events, e.g. flooding and drought, which threaten human livelihoods. In this study, the large-scale distributed variable infiltration capacity (VIC) model was used to simulate future hydrological processes in the Yarlung Zangbo River basin (YZRB), China, with a combination of the CMIP5 (Coupled Model Intercomparison Project, fifth phase) and MIROC5 (Model for Interdisciplinary Research on Climate, fifth version) datasets. The results indicate that the performance of the VIC model is suitable for the case study, and the variation in runoff is remarkably consistent with that of precipitation, which exhibits a decreasing trend for the period 2046–2060 and an increasing trend for 2086–2100. The seasonality of runoff is evident, and substantial increases are projected for spring runoff, which might result from the increase in precipitation as well as the increase in the warming-induced melting of snow, glaciers and frozen soil. Moreover, evapotranspiration exhibits an increase between 2006–2020 and 2046–2060 over the entire basin, and soil moisture decreases in upstream areas and increases in midstream and downstream areas. For 2086–2100, both evapotranspiration and soil moisture increase slightly in the upstream and midstream areas and decrease slightly in the downstream area. The findings of this study could provide references for runoff forecasting and ecological protection for similar studies in the future.     

A multi‐storage groundwater concept for the SWAT model to emphasize nonlinear groundwater dynamics in lowland catchments

Hydrological models are useful tools to analyze present and future conditions of water quantity and quality. The integrated modelling of water and nutrients needs an adequate representation of the different discharge components. In common with many lowlands, groundwater contribution to the discharge in the North German lowlands is a key factor for a reasonable representation of the water balance, especially in low flow periods. Several studies revealed that the widely used Soil and Water Assessment Tool (SWAT) model performs poorly for low flow periods. This paper deals with the extension of the groundwater module of the SWAT model to enhance low flow representation. The current two‐storage concept of SWAT was further developed to a three‐storage concept. This was realized due to modification of the groundwater module by splitting the active groundwater storage into a fast and a slow contributing aquifer. The results of this study show that the groundwater module with three storages leads to a good prediction of the overall discharge especially for the recession limbs and the low flow periods. The improved performance is reflected in the signature measures for the mid‐segment (percent bias ?2.4% vs ?15.9%) and the low segment (percent bias 14.8% vs 46.8%) of the flow duration curve. The three‐storage groundwater module is more process oriented than the original version due to the introduction of a fast and a slow groundwater flow component. The three‐storage version includes a modular approach, because groundwater storages can be activated or deactivated independently for subbasin and hydrological response unit level. Copyright © 2013 John Wiley & Sons, Ltd.     

Parameter estimation in semi‐distributed hydrological catchment modelling using a multi‐criteria objective function

Output generated by hydrologic simulation models is traditionally calibrated and validated using split‐samples of observed time series of total water flow, measured at the drainage outlet of the river basin. Although this approach might yield an optimal set of model parameters, capable of reproducing the total flow, it has been observed that the flow components making up the total flow are often poorly reproduced. Previous research suggests that notwithstanding the underlying physical processes are often poorly mimicked through calibration of a set of parameters hydrologic models most of the time acceptably estimates the total flow. The objective of this study was to calibrate and validate a computer‐based hydrologic model with respect to the total and slow flow. The quick flow component used in this study was taken as the difference between the total and slow flow. Model calibrations were pursued on the basis of comparing the simulated output with the observed total and slow flow using qualitative (graphical) assessments and quantitative (statistical) indicators. The study was conducted using the Soil and Water Assessment Tool (SWAT) model and a 10‐year historical record (1986–1995) of the daily flow components of the Grote Nete River basin (Belgium). The data of the period 1986–1989 were used for model calibration and data of the period 1990–1995 for model validation. The predicted daily average total flow matched the observed values with a Nash–Sutcliff coefficient of 0·67 during calibration and 0·66 during validation. The Nash–Sutcliff coefficient for slow flow was 0·72 during calibration and 0·61 during validation. Analysis of high and low flows indicated that the model is unbiased. A sensitivity analysis revealed that for the modelling of the daily total flow, accurate estimation of all 10 calibration parameters in the SWAT model is justified, while for the slow flow processes only 4 out of the set of 10 parameters were identified as most sensitive. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis of the hydrological behaviour of an urbanizing basin

Suburban areas undergo rapid land‐use changes due to urban growth. Consequently, the mitigation of hydrological impacts is a major issue in the field of flood and water pollution management. Nevertheless, suburban catchments have seldom been studied. This paper presents a method for analyzing the hydrological behaviour of suburban catchments; the particular method is tested on the Chézine catchment, located in a suburban area of Nantes (western France). Chézine provides a typical example of a suburban catchment, yet features the unique behaviour of a response time ranging from 1 to 6 h. It is proposed herein to classify rainfall‐runoff events in homogeneous groups according to their flow coefficient. A group of events is characterized by its mean flow coefficient and by its transfer function, which are considered as the signatures of the hydrological behaviour of these similar events. The transfer function is identified from the available series of rainfall and outflow data. The identified transfer functions serve to estimate the localization of contributing zones over the basin by estimating the basin transfer function from flowpaths. The consistency of these assumptions is then verified by comparing the estimated transfer function with the identified one. The application of this method to the Chézine catchment demonstrates that it is possible to distinguish various types of hydrological behaviour regimes associated with significantly different transfer functions. The joint analysis of the flow coefficient and transfer function of each group confirms that the Chézine catchment reacts like an urban basin with just the urban zones contributing to runoff under dry conditions. Otherwise, the wetter the initial state, the greater the tendency of this basin to react like a natural basin, as reflected by the different transfer function shapes. These results confirm the validity of the proposed method to analyse the various behaviour regimes of suburban catchments. In addition, this method helps define the specifications of hydrological models suited to suburban catchments. Copyright © 2013 John Wiley & Sons, Ltd.     

Assessing the performance of a physically based hydrological model using a proxy‐catchment approach in an agricultural environment

Physically based models are useful frameworks for testing intervention strategies designed to reduce elevated sediment loads in agricultural catchments. Evaluating the success of these strategies depends on model accuracy, generally established by a calibration and evaluation process. In this contribution, the physically based SHETRAN model was assessed in two similar U.K. agricultural catchments. The model was calibrated on the Blackwater catchment (18 km²) and evaluated in the adjacent Kit Brook catchment (22 km²) using 4 years of 15 min discharge and suspended sediment flux data. Model sensitivity to changes in single and multiple combinations of parameters and sensitivity to changes in digital elevation model resolution were assessed. Model flow performance was reasonably accurate with a Nash–Sutcliffe efficiency coefficient of 0.78 in Blackwater and 0.60 in Kit Brook. In terms of event prediction, the mean of the absolute percentage of difference (μAbs_diff) between measured and simulated flow volume (Qv), peak discharge (Qp), sediment yield (Sy), and peak sediment flux (Sp) showed larger values in Kit Brook (48% [Qv], 66% [Qp], 298% [Sy], and 438% [Sp]) compared with the Blackwater catchment (30% [Qv], 41% [Qp], 106% [Sy], and 86% [Sp]). Results indicate that SHETRAN can produce reasonable flow prediction but performs less well in estimation of sediment flux, despite reasonably similar hydrosedimentary behaviour between catchments. The sensitivity index showed flow volume sensitive to saturated hydraulic conductivity and peak discharge to the Strickler coefficient; sediment yield was sensitive to the overland flow erodibility coefficient and peak sediment flux to raindrop/leaf soil erodibility coefficient. The multiparameter sensitivity analysis showed that different combinations of parameters produced similar model responses. Model sensitivity to grid resolution presented similar flow volumes for different digital elevation model resolutions, whereas event peak and duration (for both flow and sediment flux) were highly sensitive to changes in grid size.     

Impact of land-use change on hydrological processes in the Maying River basin, China

Since the 1960s, dramatic changes have taken place in land-use patterns characterized by the persistent expansion of cultivated land and a continuous decrease in natural woodland and grassland in the arid inland river basins of China. It is very important to assess the effects of such land-use changes on the hydrological processes so vital for water resource management and sustainable development on the catchment scale. The Maying River catchment, a typical arid inland watershed located in the middle of the Hexi Corridor in northwest China, was the site chosen to investigate the hydrological responses to land-use changes. The annual runoff, base flow, maximum peak flow, and typical seasonal runoff in both spring and autumn flood periods were selected as the variables in the hydrological processes. Statistical-trend analysis and curvilinear regression were utilized to detect the trends in hydrological variables while eliminating the climatic influence. The relationship between cultivated land-use and hydrological variables was analyzed based on four periods of land-use variation data collected since 1965. A runoff model was established composed of two factors, i.e., cultivated land use and precipitation. The impact of land use changes, especially in the large ar- eas of upstream woodland and grassland turned into cultivated lands since 1967, has resulted in a mean annual runoff decrease of 28.12%, a base flow decline of 35.32%, a drop in the maximum peak discharge of 35.77%, and mean discharge decreases in spring and autumn of 36.05% and 24.87% respectively, of which the contribution of cultivated land expansion to the influence of annual runoff amounts to 77%-80%, with the contribution to the influence of spring discharge being 73%-81%, and that to the influence of base flow reaching 62%-65%. Thus, a rational regulation policy of land use patterns is vitally important to the sustainable use of water resources and the proper development of the entire catchment.     

Transferability of hydrological model parameter spaces in the estimation of runoff in ungauged catchments

Abstract

In this study, transferability options of the Hydrologiska Byråns Vattenbalansavdelning (HBV) hydrological model parameter (MP) spaces were investigated to estimate ungauged catchment runoff. Three approaches were applied in the study: MP space transfer from single, neighbouring and all potential donor catchments. The model performance was evaluated by a jackknife procedure, where one catchment at a time was treated as if ungauged, and behavioural MP sets from candidate donor catchments were used to estimate the “ungauged” runoff. The results showed that ungauged catchment runoff estimation could not be guaranteed by transferring MP sets from a single physiographically nearest donor catchment. Integrating MP sets typically from one to six donor catchments supplemented the lack of effective MP sets and improved the model performance at the ungauged catchments. In addition, the analysis results revealed that the model performance converged to an average performance when the MP sets of all potential donor catchments were integrated.     

Multireservoir system optimization in the Han River basin using multi‐objective genetic algorithms

In this study, NSGA‐II is applied to multireservoir system optimization. Here, a four‐dimensional multireservoir system in the Han River basin was formulated. Two objective functions and three cases having different constraint conditions are used to achieve nondominated solutions. NSGA‐II effectively determines these solutions without being subject to any user‐defined penalty function, as it is applied to a multireservoir system optimization having a number of constraints (here, 246), multi‐objectives, and infeasible initial solutions. Most research by multi‐objective genetic algorithms only reveals a trade‐off in the objective function space present, and thus the decision maker must reanalyse this trade‐off relationship in order to obtain information on the decision variable. Contrastingly, this study suggests a method for identifying the best solutions among the nondominated ones by analysing the relation between objective function values and decision variables. Our conclusions demonstrated that NSGA‐II performs well in multireservoir system optimization having multi‐objectives. Copyright © 2005 John Wiley & Sons, Ltd.     

A two-stage time series model for monthly hydrological projections under climate change in the Lim River basin (southeast Europe)

ABSTRACT

Climate change projections of precipitation and temperature suggest that Serbia could be one of the most affected regions in southeastern Europe. To prepare adaptation measures, the impact of climate changes on water resources needs to be assessed. Pilot research is carried out for the Lim River basin, in southeastern Europe, to predict monthly flows under different climate scenarios. For estimation of future water availability, an alternative approach of developing a deterministic-stochastic time series model is chosen. The proposed two-stage time series model consists of several components: trend, long-term periodicity, seasonality and the stochastic component. The latter is based on a transfer function model with two input variables, precipitation and temperature, as climatic drivers. The Nash-Sutcliffe model efficiency for the observed period 1950–2012 is 0.829. The model is applied for the long-term hydrological prediction under the representative concentration pathway (RCP) emissions scenarios for the future time frame 2013–2070.     

Hydrological effects of water reservoirs on hydrological processes in the East River (China) basin: complexity evaluations based on the multi‐scale entropy analysis

Using the multi‐scale entropy analysis (MSE), we study the effects of water reservoirs on the river flow records based on long streamflow series covering January 1, 1954 and December 31, 2009 at four representative hydrological stations, i.e. the Longchuan, the Heyuan, the Lingxia and the Boluo stations. Hydrological effects of two major water reservoirs, the Xinfengjiang and the Fengshuba water reservoirs, are evaluated. The results indicate that: (1) before the construction of the water reservoirs, the complexity of the streamflow series comes to be decreasing from the upper to the lower East River and which should be attributed to the topographical properties and buffering effects of the river channel; (2) construction of water reservoirs greatly increases the complexity degree of the hydrological processes, and this influence is subjected to a damping process with the increase of distance between the water reservoirs and the hydrological stations; (3) power generation is the major function of the water reservoirs in the East River basin. The results of this study should be of theoretical and scientific merits in terms of conservation of the ecological environment and also water resources management under the influences of climate changes and intensifying human activities. Copyright © 2011 John Wiley & Sons, Ltd.     

Development and application of a distributed catchment-scale hydrological model for the River Ythan,NE Scotland

Mathematical models are being used to develop a decision support system for integrated management of the Ythan catchment in NE Scotland. One component of this has involved the development of a distributed catchment-scale hydrological model. The model is based on subsurface flow routing and calculates the contribution to stream flow from each 50 m×50 m cell in the 548 km² catchment. It uses two topographic parameters, slope and distance to stream following the main line of flow, and five physical parameters. The topographic analysis and distributed flow accumulation are performed by linking the single cell model with a geographic information system. Preliminary results from a three-year simulation of daily flows indicate that the model successfully predicts the main characteristics of the catchment flow. © 1998 John Wiley & Sons, Ltd.     

Parameterization and multi‐criteria calibration of a distributed storm flow model applied to a Mediterranean agricultural catchment

The principal challenge in the parameterization of storm flow models for agricultural catchments with an artificial drainage network and fields with different degrees of tillage lies in the parsimonious definition of distributed model parameters in a way that reduces the number of calibration parameters to a justifiable minimum. This paper presents a comprehensive case study for the parameter estimation of a distributed storm flow model applied to an agricultural catchment (0.91 km²) in the Mediterranean region. Model parameterization was combined with procedures for multi‐criteria, multi‐storm calibration, where we automatically calibrated three parameters related to flow velocity and infiltration, and compared single and multi‐storm criteria that are based on discharge volume, peak flow, and the Nash–Sutcliffe coefficient. Multi‐storm calibration yielded a set of parameter values for the simulation batch with best multi‐storm overall performance, which are close to the median values in the pre‐calibration of individual storms. Our results suggest that flow velocities and proportionality of the channel infiltration rate do not vary significantly over the course of 11 years. Copyright © 2012 John Wiley & Sons, Ltd.     

Potential of time‐lapse photography of snow for hydrological purposes at the small catchment scale

Time‐lapse photography provides an attractive source of information about snow cover characteristics, especially at the small catchment scale. The objective of this study was to design and test a monitoring system, which allows multi‐resolution observations of snow cover characteristics. The main aim was to simultaneously investigate the spatio‐temporal patterns of snow cover, snow depth and snowfall interception in the area very close to the camera, and the spatio‐temporal patterns of snow cover in the far range. The multi‐resolution design was tested at three sites in the eastern part of the Austrian Alps (Hochschwab‐Rax region). Digital photographs were taken at hourly time steps between 6:00 and 18:00 in the period November, 2004 to December, 2006. The results showed that the time‐lapse photography allows effective mapping of the snow depths at high temporal resolution in the region close to the digital camera at many snow stake locations. It is possible to process a large number of photos by using an automatic procedure for accurate snow depth readings. The digital photographs can also be used to infer the settling characteristics of the snow pack and snow interception during the day. Although it is not possible to directly estimate the snow interception mass, the photos may indeed give very useful information on the snow processes on and beneath the forest canopy. The main advantage of using time‐lapse photography in the far range of the digital camera is to observe the spatio‐temporal patterns of snow cover over different landscape configurations. The results illustrate that digital photographs can be very useful for parameterising processes such as sloughing on steep slopes, snow deposition in gullies and snow erosion on mountain ridges in a distributed snow model. Copyright © 2011 John Wiley & Sons, Ltd.     

Fine scale mapping of fractional tree canopy cover to support river basin management

Management of water, regionally, nationally and globally will continue to be a priority and complex undertaking. In riverine systems, biotic components like flora and fauna play critical roles in filtering water so it is available for human use and consumption. Preservation of ecosystems and associated ecosystem functions is therefore vital. In highly regulated large river basins, natural ecosystems are often supported through provision of environmental flows. Flow delivery, however, should be underpinned by rigorous monitoring to identify and prioritise biotic water requirements. Currently, large-scale monitoring solutions are scaled from remote sensing data via measurement of field evapotranspiration for woody tree vegetation species. However, as there is generally a mismatch between field data collection area and remote sensing pixel size, new methods are required to proportion tree evapotranspiration based on tree fractional canopy area per pixel. We present a novel method to derive tree fractional canopy cover (FTCC) at 20 m resolution in semi-arid and arid floodplain areas. The method employs LiDAR as a canopy area field measurement proxy (10 m resolution). We used Sentinel-1 and Sentinel-2 (radar and multispectral imagery) in a Random Forest analysis, undertaken to develop a predictive FTCC model trained using LiDAR for two regions in the Murray–Darling Basin. A predictor model combining the results of both regions was able to explain between 71%–85% of FTCC variation when compared to LiDAR FTCC when output in 10% increments. Development of this method underpins the advancement of woody vegetation monitoring to inform environmental flow management in the Murray–Darling Basin. The method and fine scale outputs will also be of value to other catchment management concerns such as altered catchment water yields related to bushfires and as such has application to water management worldwide.