bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved annual rainfall-runoff forecasting using PSO–SVM model based on EEMD
Authors: Wang Wen-chuan , Xu Dong-mei , Chau Kwok-wing , Chen Shouyu
Published: December 2015

Rainfall-runoff simulation and prediction in watersheds is one of the most important tasks in water resources management. In this research, an adaptive data analysis methodology, ensemble empirical mode decomposition (EEMD), is presented for decomposing annual rainfall series in a rainfall-runoff model based on a support vector machine (SVM). In addition, the particle swarm optimization (PSO) is used to determine free parameters of SVM. The study data from a large size catchment of the Yellow River in China are used to illustrate the performance of the proposed model. In order to measure the forecasting capability of the model, an ordinary least-squares (OLS) regression and a typical three-layer feed-forward artificial neural network (ANN) are employed as the benchmark model. The performance of the models was tested using the root mean squared error (RMSE), the average absolute relative error (AARE), the coefficient of correlation (R) and Nash–Sutcliffe efficiency (NSE). The PSO–SVM–EEMD model improved ANN model forecasting (65.99%) and OLS regression (64.40%), and reduced RMSE (67.7%) and AARE (65.38%) values. Improvements of the forecasting results regarding the R and NSE are 8.43%, 18.89% and 182.7%, 164.2%, respectively. Consequently, the presented methodology in this research can enhance significantly rainfall-runoff forecasting at the studied station.
A preprocessing program for a distributed hydrological model: development and application
Authors: Li Lei , Xu Zongxue , Li Yanli , Liu Wenfeng , Zhang Lanying
Published: December 2015

A preprocessing program for a distributed hydrological model is very important because it will greatly influence the results of runoff simulation. Runoff simulations include several procedures, such as the determination of flow directions, definition of runoff routing orders, estimation of flow accumulation areas and extraction of drainage networks, etc. In order to simplify the development work and to improve the efficiency of model development, a preprocessing program was developed that can work independently with a graphic user interface. Only digital elevation model (DEM) data are required in this program and characteristics of the program include the following components: (1) a method for the determination of flow direction without sink filling; (2) a leaf clipping method for watershed partitioning; and (3) the determination of the order of runoff routing according to a top-down method. Finally, a case study in the Lhasa River basin is presented, and three case studies in the Wei River, Zhangweinan River and Sanchuan River basins are selected to validate the program. The results show that disconnected or parallel drainage networks can be avoided by using the preprocessing program, especially in flat areas, which can significantly improve the development of distributed hydrological models.
Numerical assessment of bed-load discharge formulations for transient flow in 1D and 2D situations
Authors: Juez Carmelo , Murillo Javier , García-Navarro Pilar
Published: December 2015

Two-dimensional (2D) transient flow over an erodible bed can be modelled using shallow-water equations and the Exner equation to describe the morphological evolution of the bed. Considering the fact that well-proven capacity formulae are based on one-dimensional (1D) experimental steady flows, the assessment of these empirical relations under unsteady 1D and 2D situations is important. In order to ensure the reliability of the numerical experimentation, the formulation has to be general enough to allow the use of different empirical laws. Moreover, the numerical scheme must handle correctly the coupling between the 2D shallow-water equations and the Exner equation under any condition. In this work, a finite-volume numerical scheme that includes these two main features will be exploited here in 1D and 2D laboratory test cases. The relative performances of Meyer-Peter and Müller, Ashida and Michiue, Engelund and Fredsoe, Fernandez Luque and Van Beek, Parker, Smart, Nielsen, Wong and Camenen and Larson formulations are analysed in terms of the root mean square error. A new discretization of the Smart formula is provided, leading to promising predictions of the erosion/deposition rates. The results arising from this work are useful to justify the use of an empirical sediment bed-load discharge formula among the ones studied, regardless of the hydrodynamic situation.
Development of a real-time regional-inundation forecasting model for the inundation warning system
Authors: Lin Gwo-Fong , Lin Hsuan-Yu , Chou Yang-Ching
Published: December 2015

Accurate forecasts of the inundation depth are necessary for inundation warning and mitigation. In this paper, a real-time regional forecasting model is proposed to yield 1- to 3-h lead time inundation maps. First, the K-means based cluster analysis is developed to group the inundation depths and to indentify the control points. Second, the support vector machine is used as the computational method to develop the point forecasting module to yield inundation forecasts for each control point. Third, based on the forecasted depths and the geographic information, the spatial expansion module is developed to expand the point forecasts to the spatial forecasts. An actual application to Siluo Township, Taiwan, is conducted to demonstrate the advantage of the proposed model. The results indicate that the proposed model can provide accurate inundation maps for 1- to 3-h lead times. The accurate long lead time forecasts can extend the lead time to allow sufficient time to take emergency measures. Furthermore, the proposed model is an efficient process that can be trained rapidly with real-time data and is more suitable to be integrated with the decision support system. In conclusion, the proposed modeling technique is expected to be useful to support the inundation warning systems.
Modelling the effect of water diversion projects on renewal capacity in an urban artificial lake in China
Authors: Gao Xueping , Xu Liping , Zhang Chen
Published: December 2015

To improve the water environment, manual water diversion projects were scheduled to bring freshwater to an urban artificial lake to dilute and divert pollutants out of the lake. A three-dimensional numerical model was used to study the effect of diversion schemes on the transport of dissolved substances by using concepts of water renewal time and water age. The model results showed that the impact of diversion schemes on transport processes was strongly influenced by hydrodynamic conditions induced by inflow/outflow discharges. Shorter water timescales occupied the west and east lake, implying a faster water renewal occurrence therein. Water ages were highly variable, both spatially and temporally. Longer water age was exhibited in the inner lake and bays. An exchange rate of 89.3% was obtained at the 5 m3/s discharge condition under 60 days' duration, with integral renewal time of approximately 50 days. The distribution of water age showed that it only took less than 10 days for the substance discharged at the inlets to be transported to the outlets. The results offer useful information for understanding the efficiency of water exchange by diversion projects and can be used to estimate the water renewal capacity for environmental assessment purposes.
A web-based environmental decision support system for legacy models
Authors: Kumar Saurav , Godrej Adil N. , Grizzard Thomas J.
Published: December 2015

An environmental decision support system (EDSS) was designed for the Occoquan system in Northern Virginia, USA. This EDSS is available through the internet using web-browsers, and enables stakeholders to interact with complexly-linked water resources models for the Occoquan system based on seven implementations of HSPF and two implementations of CE-QUAL-W2 software. Using the web-interface of the EDSS, users may delineate land use changes and simulate the water quality impact of such changes by remotely executing the water resources models. The EDSS utilizes a server cluster to share the computational load of simultaneously executing multiple instances of the linked Occoquan system models along with methods to limit ‘similar’ model executions. The server cluster was assembled from disparate machines with spare computing resource available on the local network, thereby eliminating the need for any additional hardware to execute an increased number of model simulations. It is expected that the enhanced accessibility to the water resources models through the EDSS may allow stakeholders to use the models as a planning and educational resource, without direct expert modeler's involvement. Further, this EDSS is comprised of modules that may be extended to other watersheds with similar legacy, calibrated modeling systems.
Estimating burst probability of water pipelines with a competing hazard model
Authors: Shin H. , Kobayashi K. , Koo J. , Do M.
Published: December 2015

Because pipeline systems represent more than 80% of the total asset value of water-distribution systems, their management is an important issue for water utilities. A pipeline deteriorates over time after installation and, along with the deterioration, pipe bursts can occur as various types, and the choice of a maintenance and repair strategy will depend on the burst types. It is therefore important to forecast the occurrence probability of each burst type. This paper addresses a competing deterioration-hazard model that allows modelling of deterioration by multiple types of failure and focuses on the bursts which occur in the pipe body or connection. The Weibull hazard model is used to address the lifetime of each pipeline, measured from when it was buried, and the model takes into account the competing nature of various types of failure by using a competing hazard model. The competing deterioration-hazard model allows us to determine the probability of deterioration in the pipe body and connection. The model is estimated by Bayesian inference using a Markov chain Monte Carlo method. The applicability of the method to data for an existing pipeline system is examined.
Improving predictions made by ANN model using data quality assessment: an application to local scour around bridge piers
Authors: Choi Sung-Uk , Choi Byungwoong , Choi Seongwook
Published: December 2015

The scour depth that develops around bridge piers is known to be related to flow intensity, particle size of bed sediment, and pier dimensions. Earlier approaches to this issue have mainly relied on empirical formulas. Even numerical simulations have not been so successful due to problems associated with interactions between water flow and streambed morphology. This necessitates the application of an artificial intelligence (AI)-type approach to understanding the effects of local scour around bridge piers. Although previous studies reported that AI-based models are better predictors, they do not predict field-scale local scour well. Motivated by this, the present study reports on the use of data quality assessment with an artificial neural network (ANN) model for predicting field-scale scour depth around bridge piers. Both univariate and multivariate methods were applied and the predicted results are compared. For the multivariate method, the Euclidean distance method and Mahalanobis distance method were used and the predicted results are compared. The ANN model was first trained and validated using laboratory data and the model was applied to data obtained in laboratory experiments. The model was then applied to field data. Quantitative descriptions are given on how much the data quality assessment improves predictions based on the use of the ANN model.
Rainwater harvesting as source control option to reduce roof runoff peaks to downstream drainage systems
Authors: Campisano Alberto , Modica Carlo
Published: December 2015

The objective of the paper is to evaluate the potential of tank-based rainwater harvesting systems in free standing houses as the source control method to mitigate peak roof runoff due to rainfall in urban areas. To this aim, the water balance simulation of the rainwater tank was carried out using both high resolution rainfall series and toilet water demand data extracted from the database of results built in a previous field campaign involving six experimental households in southern Italy. Simulations show that significant potential for runoff peak reduction exists, basically depending on the rainwater tank size and on the characteristics of the water demand in the house.
Self-organizing map clustering technique for ANN-based spatiotemporal modeling of groundwater quality parameters
Authors: Nourani Vahid , Alami Mohammad Taghi , Vousoughi Farnaz Daneshvar
Published: December 2015

The present study integrates co-kriging as spatial estimator and self-organizing map (SOM) as clustering technique to identify spatially homogeneous clusters of groundwater quality data and to choose the most effective input data for feed-forward neural network (FFNN) model to simulate electrical conductivity (EC) and total dissolved solids (TDS) of groundwater. The methodology is presented in three stages. In the first stage, a geostatistics approach of co-kriging is used to estimate groundwater quality parameters at locations where the groundwater levels are measured. In stage two, a SOM clustering technique is used to identify spatially homogeneous clusters of groundwater quality data. The dominant input data, selected by spatial clustering and mutual information are then imposed into the FFNN model for one-step-ahead predictions of groundwater quality parameters at stage three. The performance of the newly proposed model is compared to a conventional linear forecasting method of multiple linear regression (MLR). The results suggest that the proposed model decreases dimensionality of the input layer and consequently the complexity of the FFNN model with acceptable efficiency in spatiotemporal simulation of groundwater quality parameters. The application of FFNN for modeling EC and TDS parameters increases the accuracy of predictions respectively up to 84.5% and 17% on average with regard to the MLR model.
A flexible methodology to sectorize water supply networks based on social network theory concepts and multi-objective optimization
Authors: Campbell Enrique , Izquierdo Joaquín , Montalvo Idel , Ilaya-Ayza Amilkar , Pérez-García Rafael , Tavera Mario
Published: December 2015

A novel methodology to sectorize water supply networks (WSNs) depending on a main transmission line is presented in this paper. The methodology is based on concepts derived from the social network theory and graph theory (namely, community detection and shortest path respectively); and also on a multi-objective optimization process by means of agent swarm optimization (ASO). A series of energy, operative, and economic criteria are optimized in this process. The core idea is to form sectors over the distribution network based on communities found using a community detection algorithm (Walktrap). The methodology is flexible and enables the technical staff in water utilities to make decisions at different stages. It has been tested by generating four feasible solutions over a portion of a real WSN.
Sediment load prediction by combined fuzzy logic-wavelet method
Authors: Özger Mehmet , Kabataş Mehmet Burak
Published: December 2015

Sediment load prediction is very important in planning, operation, and maintenance of water structures located on rivers. The sediment loads exhibit random characteristics due to the uncertain nature of sediment transportation in rivers. To predict suspended sediment load, stochastic processes, regression methods, neural network models, and fuzzy logic have been used in the literature so far. The purpose of this study was to develop a model that can make accurate predictions of suspended sediment loads. Here, a combination of wavelet and fuzzy logic techniques (WFL) is proposed as a new technique to model the behavior of sediment load. While the wavelet method is able to decompose the original series into its sub-bands, fuzzy logic method can be used as a predictive model for each sub-band. It is possible to detect significant power at specific intervals from average wavelet spectra. The WFL was compared with the stand-alone fuzzy logic approach based on the Nash–Sutcliffe Sufficiency Score (NSSS), mean absolute error (MAE), and square of correlation coefficient (R) used as performance indicators. The results of the study show that the WFL provides a considerable improvement over the stand-alone fuzzy logic approach in the prediction of sediment load.
Dams induced stage–discharge relationship variations in the upper Yangtze River basin
Authors: Mei Xuefei , Dai Zhijun , Wei Wen , Gao Jinjuan
Published: December 2015

Although stage–discharge relationships are crucial for discharge estimations and hydrological analyses, few efforts have been taken to assess their temporal alterations in the context of dam regulation. Here, the upper Yangtze River basin serves as an example to demonstrate the influence of hydraulic structures on stage–discharge relationships evolution. Daily records of water level and river discharge from 1950 to 2013 at Yichang hydrometric station were grouped and analyzed. Back-propagation artificial neural network was used to model the stage–discharge relationships. The obtained curves revealed substantial shifts since the Gezhouba Dam (GD) and Three Gorges Dam (TGD) were put into practice sequentially. In low flow scenarios, the decline of water levels due to GD and TGD regulation were variable with river discharge, whereas in normal flow scenarios, the rating curves indicate equilibrium state with almost the same slopes regardless of GD and TGD influence. In high flow scenarios, the rating curves representing natural condition, GD, and TGD regulation intersect with each other. Moreover, the detected changes in stage–discharge relationship were mainly in response to dam regulation, channel erosion and sand exploitation, while irrelevant to precipitation variability. The contribution of sand mining, GD regulation, and TGD regulation on rating curve variations at Yichang station were 36%, 11%, and 53%, respectively.
Use of very high resolution climate model data for hydrological modelling: estimation of potential evaporation
Authors: Rudd Alison C. , Kay Alison L.
Published: December 2015

Climate model data are increasingly used to drive hydrological models, to assess the possible impacts of climate change on river flows. Hydrological models often require potential evaporation (PE) from vegetation, alongside precipitation, but PE is not usually output by climate models so has to be estimated from other meteorological variables. Here, the Penman–Monteith formula is applied to estimate PE using data from a 12 km Regional Climate Model (RCM) and a nested very high resolution (1.5 km) RCM covering southern Britain. PE estimates from RCM runs driven by reanalysis boundary conditions are compared to observation-based PE data, to assess performance. The comparison shows that both the 1.5 and 12 km RCMs reproduce observation-based PE well, on daily and monthly time-steps, and enables choices to be made about application of the formula using the available data. Data from Current and Future RCM runs driven by boundary conditions from a Global Climate Model are then used to investigate potential future changes in PE, and how certain factors affect those changes. In particular, the importance of including changes in canopy resistance is demonstrated. PE projections are also shown to vary to some extent according to how aerosols are modelled in the RCMs.
Temporal variations of streamflow in a mid-latitude Eurasian steppe watershed in the past half century
Authors: Wang Xixi
Published: December 2015

Previous studies either did not identify abrupt change or identified such change but did not exclude it from the detection of trend in streamflow. As a result, an overall downward trend might be erroneously detected as an upward trend because of abrupt increase, while an overall upward trend could be faked as a downward trend due to abrupt decrease. The objectives of this study were to: (1) present a methodology to analyze trend in streamflow in the presence of abrupt change; and (2) use this methodology to detect trend and extreme occurrence of streamflow in the Upper Balagaer River watershed, a mid-latitude nearly pristine precipitation-fed Eurasian steppe watershed in north China. The results indicate that streamflow abruptly decreased around 1994 and exhibited no significant trend from 1960 to 1993 but a significant decrease trend since 1994 (in particular after 1999). In addition, the occurrence of days with a low streamflow was greater after 1994, whereas the occurrence of days with a high streamflow was smaller. Further, the inclusion of the abrupt change in the analysis could compound the detection of the pre-1994 trends but had minimal influences on the detection of the post-1994 trends. These results can be representative across the Eurasian steppe region beyond the study watershed.
Reversing hydrology: quantifying the temporal aggregation effect of catchment rainfall estimation using sub-hourly data
Authors: Kretzschmar A. , Tych W. , Chappell N. A. , Beven K. J.
Published: December 2015

Inferred rainfall sequences generated by a novel method of inverting a continuous time transfer function show a smoothed profile when compared to the observed rainfall, however, streamflow generated using the inferred catchment rainfall is almost identical to observed streamflow (Rt2 > 97%). This paper compares the effective rainfall inferred by the regularised inversion process (termed inferred effective rainfall (IER)) proposed by the authors with effective rainfall derived from the observed catchment rainfall (termed observed effective rainfall (OER)) in both time and frequency domains in order to confirm that, by using the dominant catchment dynamics in the inversion process, the main characteristics of catchment rainfall are being captured by the IER estimates. Estimates of the resolution of the IER are found in the time domain by comparison with aggregated sequences of OER, and in the frequency domain by comparing the amplitude spectra of observed and IER. The temporal resolution of the rainfall estimates is affected by the slow time constant of the catchment, reflecting the presence of slow hydrological pathways, for example, aquifers, and by the rainfall regime, for example, dominance of convective or frontal rainfall. It is also affected by the goodness-of-fit of the original forward rainfall–streamflow model.
The hydrological performance of bioretention cells in regions with cold climates: seasonal variation and implications for design
Authors: Paus Kim H. , Muthanna Tone M. , Braskerud Bent C.
Published: December 2015

Three bioretention cells in Norway were monitored for 23 to 36 months to evaluate the hydrological performance of bioretention cells operated in regions with cold climates and to test if cell size equations can be used to predict hydrological performance. Values of saturated hydraulic conductivity (Ksat) were determined for separate events by analyzing the observed infiltration rates and via infiltration tests. The two cells with the highest Ksat values (15.9 and 45.0 cm/h) performed excellently during the study period infiltrating nearly all of the incoming runoff. In contrast, the cell with low Ksat value (1.3 cm/h) infiltrated barely half of the incoming runoff. The latter cell had a clear seasonal variation in hydrological performance relating to changes in the Ksat values over the year. The size equation that gave the best predictions of the observed hydrological performance accounts for both surface storage and infiltration. By using this equation to evaluate various bioretention cell designs, it was found that the most effective way to increase the hydrologic performance is to have a Ksat value above 10 cm/h.
Contribution of glacial melt to river runoff as determined by stable isotopes at the source region of the Yangtze River, China
Authors: Liu Zhaofei , Yao Zhijun , Wang Rui
Published: December 2015

The primary objective of this study was to quantify the contribution of glacial melt to total runoff in the Gaerqu River catchment, which is located in the source region of the Yangtze River, China. The isotope hydrograph separation method was used to separate glacier melt runoff from total runoff in the catchment. The degree-day method was used to investigate temporal variations in glacial melt runoff. The results showed that the contribution of glacial melt runoff to total runoff was 15.0%. The uncertainty of the separation was ± 3.7% at the confidence level of 95%. Glacial melt runoff was mainly generated in June, July, and August. The runoff coefficient was 0.23 for the catchment. Precipitation-induced runoff constituted 19.9% of the total precipitation, meaning that precipitation loss was >80% across the study period (a hydrological year). The Local Meteoric Water Line (LMWL) of the catchment was fitted as δ2H = 7.75 δ18O + 5.93. This line has a smaller slope and intercept than the Global Meteoric Water Line. The regression-lines for the δ18O and δ2H values of stream water indicated that evaporation was greater over the entire catchment than it was for the upstream region alone.
Assessing differences in snowmelt-dependent hydrologic projections using CMIP3 and CMIP5 climate forcing data for the western United States
Authors: Ficklin Darren L. , Letsinger Sally L. , Stewart Iris T. , Maurer Edwin P.
Published: December 2015

Most recent climate change impact studies are using Coupled Model Intercomparison Project Phase 5 (CMIP5) projections to replace older generation CMIP3 projections. Here we evaluate whether differences between projections based on comparable high emission pathways of a seven-member general circulation model CMIP3 versus CMIP5 ensemble change our understanding of the expected hydrologic impacts. This work focuses on the important snowmelt-dominated mountain runoff-generating regions of the western United States (WUS; Upper Colorado River Basin (UCRB), Columbia River Basin (CRB), and Sierra Nevada (SN) Basins). Significant declines in snowmelt, and shifts in streamflow timing owing to warmer, wetter CMIP5 projections match or exceed those based on CMIP3 throughout the WUS. CMIP3- and CMIP5-based projections, while generally in agreement about hydroclimatic changes, differ in some important aspects for key regions. The most important is the UCRB, where CMIP5-based projections suggest increases in future streamflows. Comparable hydrologic projections result from similar underlying climate signals in CMIP3 and CMIP5 output for the CRB and SN, suggesting that previous work completed in these basins based on CMIP3 projections is likely still useful. However, UCRB hydrologic projections based on CMIP5 output suggest that a re-evaluation of future impacts on water resources is warranted.
Hydrological modelling under climate change considering nonstationarity and seasonal effects
Authors: Kim Kue Bum , Kwon Hyun-Han , Han Dawei
Published: December 2015

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.
A novel approach for designing large-scale river temperature monitoring networks
Authors: Jackson F. L. , Malcolm I. A. , Hannah David M.
Published: December 2015

Water temperature is an important control on processes in aquatic systems and particularly for freshwater fish, affecting growth, survival and demographic characteristics. In recognition of this importance, the Scottish Government has prioritised developing a robust national river temperature monitoring network. Advances in geographical information systems, spatial statistics and field data loggers make large-scale river temperature monitoring increasingly possible. However, duplication of environmental and thermal characteristics among monitoring sites means many networks have lower than expected statistical power. This paper describes a novel methodology for network design, illustrated by the development of the Scotland River Temperature Monitoring Network. A literature review identified processes controlling stream temperature and associated landscape controls. Metrics indicative of these landscape controls were calculated for points every 500 m along the river network. From these points, sites were chosen to cover the full range of observed environmental gradients and combinations of controlling variables. The resulting network contains sites with unique characteristics covering the range of relevant environmental characteristics observed in Scottish salmon rivers. The network will thus have minimal redundancy, often not seen in large networks, and high statistical power to separate the relative importance of predictor variables thereby allowing large-scale water temperature predictions.
Characterization of dynamic evolution of the spatio-temporal variation of rain-field in Hong Kong
Authors: Liu Peng , Tung Yeou-Koung
Published: December 2015

A significant part of Hong Kong has hilly terrain with relatively short flow concentration time and, hence, is susceptible to the threat of flash floods and landslides during intense convective thunderstorms and tropical cyclones. For places like Hong Kong, a rainfall model that could adequately capture small-scale temporal and spatial variations would be highly desirable. The main challenge in rain-field modeling is to capture and describe the dynamic time-space evolution of the rainfall during rainstorm events. In this study, radar data with a high spatial (1 km2) and temporal (6 min) resolution of four rainstorm events in Hong Kong are analyzed. A geostatistical approach based on indicator variograms of rain-fields is used. The spatial structure of a rain-field is found to be highly anisotropic and should be adequately considered in the model. Variability of the spatial structure of a rain-field was described well by the main features of the variograms. Moreover, it is possible to identify whether multiple rainstorm centers exist by comparing the mean length and range. In order to establish reliable statistics on the spatial and temporal structure of rain-fields in Hong Kong, this approach could be applied to a large set of rainstorm events in this same region in the future.
Projection of future streamflow changes of the Pearl River basin in China using two delta-change methods
Authors: Yuan Fei , Tung Yeou-Koung , Ren Liliang
Published: December 2015

Considerable biases in precipitation simulations in climate models have required the adoption of delta-change approaches to construct future precipitation scenarios for hydrological climate change impact studies. However, different delta-change methods yield different future precipitation scenarios that might significantly affect the projected future streamflow. To assess these effects, two delta-change methods were compared: the simple delta-change (SDC) method with a constant scaling factor and the quantile-quantile delta-change (QQDC) method with a quantile mapping-based non-uniform delta factor. The Xinanjiang (XAJ) hydrological model was applied using historical climatic data and two future precipitation scenarios for streamflow simulations in the Pearl River basin, China. The results show that the two delta-change methods have significant influences on future precipitation and streamflow projections, and these impacts become more distinct at finer and extreme event time scales. For instance, the QQDC method projects the 20-year daily maximum precipitation to be 8.1–98.6% higher than the SDC method. Consequently, the XAJ model with the QQDC future precipitation produces the 20-year daily maximum streamflow to be approximately 7.0–65.0% higher than that using the SDC precipitation. It implies that future precipitation transformation methods are a source of uncertainty, affecting future discharge projections. Such uncertainty should be considered in water resources management and flood control strategies for future climate change adaptations.
Integration of the rice paddy water management into a coupled surface-subsurface water flow model in the Sakuragawa River watershed (Japan)
Authors: Sagehashi Masaki , Mori Hiroko , Hareyama Yuta , Sakuma Kazuyuki , Akiba Michihiro , Hosomi Masaaki
Published: December 2015

Rice paddy water management was integrated into a distributed three-dimensional surface and subsurface coupling hydrological model of the Sakuragawa River watershed. This watershed is located in the Kanto Plain in Japan and includes the hillside of Mt. Tsukuba. Therefore, this watershed includes both steep mountainous areas and rice paddy-dominated flat land. Thus, water management of rice paddies is important and was calculated separately using a paddy model. The use of groundwater for rice paddy irrigation was considered as well as a water supply from outside of the watershed (Kasumigaura Lake). The model parameters were calibrated and validated with reference to the predictability of river water flow and the groundwater level. Using the calibrated model, three-dimensional streamlines, water travel time distributions, and water balance in some grids were clarified. The developed model will facilitate sustainable water resource management in the watershed.
Influence of rainfall interception by endemic plants versus short cycle crops on water infiltration in high altitude ecosystems of Ecuador
Authors: Janeau J. L. , Grellier S. , Podwojewski P.
Published: December 2015

Owing to their high water retention, the volcanic ash-soils of the Northern Andean highlands (páramos) can be considered as natural ‘water storage tanks’ for drinking water and for irrigation. Vegetation plays an important role in transferring rain to the soil and in controlling the soil water content. To assess this role, we quantified the stemflow process under rainfall simulations for seven of the main plants along an altitude gradient on the Pichincha volcano in Ecuador. The volume of water transferred into the soil was higher at the lower rainfall intensity than at the higher intensity. The results were compared to the stemflow measured with potato and maize crops growing in the lower altitude range. The results showed that the relative volume of stemflow increased with altitude from 8% in the crop area to 58% in the upper part of the catena. Low values of stemflow were associated with potatoes and maize annual short-cycle crops while high values were associated with the natural vegetation. For cultivated crops rainwater interception by stemflow delayed the soil surface crusting and runoff process. This study shows that rainwater interception by vegetation is of great importance for soil water recharge in these Andisols.
Modeling the combined impact of future climate and land use changes on streamflow of Xinjiang Basin, China
Authors: Yan Renhua , Huang Jiacong , Wang Yan , Gao Junfeng , Qi Lingyan
Published: December 2015

The response of hydrologic circulation to climate and land use changes is important in studying the historical, present, and future evolution of aquatic ecosystems. In this study, the Coupled Model Inter-comparison Project Phase 5 multi-model ensemble and a raster-based Xin'anjiang model were applied to simulate future streamflows under three climate change scenarios and two land use/cover change conditions in the Xinjiang Basin, China, and to investigate the combined effect of future climate and land use/cover changes on streamflow. Simulation results indicated that future climate and land use/cover changes affect not only the seasonal distributions of streamflow, but also the annual amounts of streamflow. For each climate scenario, the average monthly streamflows increase by more than 4% in autumn and early winter, while decreasing by more than −26% in spring and summer for the 21st century. The annual streamflows present a clear decreasing trend of −27%. Compared with land use/cover change, climate change affects streamflow change more. Land use/cover change can mitigate the climate change effect from January to August and enhance it in other months. These results can provide scientific information for regional water resources management and land use planning in the future.
The role of extreme events in reaching adaptation tipping points: a case study of flood risk management in Dhaka, Bangladesh
Authors: Ahmed Farhana , Gersonius Berry , Veerbeek William , Alam Khan M. Shah , Wester Philippus
Published: December 2015

Adaptation tipping points (ATPs) refer to the situation where a policy or management strategy is no longer sufficient, and adjustments or alternative policies/strategies have to be considered. In developed countries, the main focus of research has been on characterising the occurrence of ATPs in the face of slow variables like climate change. In developing countries, the system characteristics that lead to ATPs are more uncertain and typically comprise a combination of drivers. It is well recognised that policies and management strategies have often shifted in the wake of extreme events like floods. By focusing on flood risk management (FRM), this paper explores the role of sudden or extreme events and other drivers that trigger ATPs. It analyses the historical flooding pattern of Dhaka and policies relevant to FRM, and determines the tipping points for policy-making. A timeline has been established between the flood events, co-drivers, policy interventions and institutional reforms over the last 50 years. ATPs in a developing country context have been found to result from hydrological factors and uncontrolled urban growth as well as foreign intervention, non-implementation or untimely implementation of planned measures and fund constraints.
An institutional and socio-cultural perspective on the adaptation pathways approach
Authors: van der Brugge Rutger , Roosjen Ronald
Published: December 2015

The uncertainties surrounding climate change are creating challenges for policy makers with regard to investments in water-related infrastructure. A promising new approach is the adaptation pathways approach. This article contributes to this approach by introducing an institutional and socio-cultural perspective. It presents an analytical framework to evaluate the necessary institutional and socio-cultural conditions, uncovering challenges with regard to the governance of adaptation and of keeping options open for the future. The framework has been applied to the case study of fresh water supply in the Netherlands. Based on an institutional and socio-cultural analysis, the feasibility, flexibility and governance of adaptation strategies are discussed. Reflecting on the presented framework, critical issues are addressed with regard to the further development of the adaptation pathways approach.
A grid-based integrated surface–groundwater model (GISMOD)
Authors: Li Lei , Xu Zongxue , Zuo Depeng , Zhao Jie
Published: December 2015

A distributed hydrological model, the Grid-based Integrated Surface-groundwater MODel (GISMOD), was developed to simulate hydrological processes by considering water interaction among different soil layers. The model integrates six modules. Basic information on catchment, such as the flow direction and the drainage network, can be obtained automatically from digital elevation model (DEM) data by using the preprocessing module. In GISMOD, three methods are available to estimate precipitation and eight to estimate evapotranspiration in each grid. Infiltration excess flow, saturation flow, recharge flow from soil and groundwater are all considered by using a simplified method according to the three-layer structure of GISMOD. A case study in the upper-middle reaches of the Heihe River was presented to evaluate the model performance. The results show that the change tendencies of infiltrated water and recharged water are opposite in the study area; the surface water is mainly infiltrated to the soil layer in the upper streams, and then discharged by groundwater in the middle reaches, which is more consistent with the actual situation in the Heihe River basin. In addition, the simulated runoff of a river grid near the Yingluoxia hydrological station is compared with the observed one and the results also demonstrate that GISMOD has a better performance in runoff estimation on both daily and monthly scales.
Temporal-spatial evolution patterns of the annual precipitation considering the climate change conditions in the Sanjiang Plain
Authors: Fu Qiang , Li Tianxiao , Li Tienan , Li Heng
Published: December 2015

The wavelet theory, Mann-Kendall trend test and ArcGIS spatial analysis theory were used to analyze annual precipitation and mean temperature data that were collected at seven national weather stations in the Sanjiang Plain from 1956 to 2013 to identify the temporal-spatial patterns of annual precipitation changes caused by climate change conditions. The results showed that the climate in the Sanjiang Plain experienced a significant warming trend over the past 50 years, with the temperature increasing by 1.35 °C since the 1960s. Additionally, the precipitation also exhibited certain trend characteristics, which revealed a larger difference in different areas. The annual precipitation exhibited 23-year and 12-year periodic variation characteristics, and the period with above-average annual precipitation levels is expected to continue after 2013. The spatial distributions of the mean annual precipitation for different years were different, whereas the spatial distribution of the multi-year mean precipitation was relatively uniform. The annual variation amplitude of the annual precipitation in the central area was larger than that in the south. The overall inter-annual fluctuation of the annual precipitation was relatively small with a mostly normal distribution. The results can provide guidance for scientific investigations and the reasonable use of rainfall resources in the Sanjiang Plain.
Variability of GPS water vapor associated with warming activity in Peninsular Malaysia during the period of 2008–2011
Authors: Suparta Wayan , Muhammad Maszidah , Jit Singh Mandeep Singh , Tangang Fredolin T. , Abdullah Mardina , Tariqul Islam Mohammad
Published: December 2015

This study utilizes the precipitable water vapor (PWV) parameter retrieved from ground-based global positioning system (GPS) to detect warming activity in Peninsular Malaysia from 2008 to 2011. Daily average of GPS PWV and surface meteorology data taken from six selected stations over Peninsular Malaysia are analyzed. Prior to warming detection, GPS PWV results are compared with PWV obtained from Radiosonde and found a positive relationship. The daily GPS PWV variability was characterized as high during the inter-monsoon seasons (April-May and October-November) and lower at the beginning, middle and the end of the year. For the monthly variations, GPS PWV increased by about 2.40 mm, which is correlated with an increase in surface temperature of 0.20 °C. We detected variability of PWV with a semiannual variation and the pattern is opposite to the accumulated precipitation, indicating that wet and dry spells coincide with local monsoon and intermonsoon periods. The warming effect in this study was felt over all selected stations with northern parts of Peninsular Malaysia affected significantly. The results imply that GPS is a powerful tool for analysis of warming effects and the mechanism of how it affects the circulation of water vapor is discussed in this study.
Detection and attribution of seasonal temperature changes in India with climate models in the CMIP5 archive
Authors: Sonali P. , Nagesh Kumar D.
Published: December 2015

This study analyzes the change in annual and seasonal maximum and minimum temperature (Tmax and Tmin) during the period 1950–2005 (i.e., second half of the 20th century). In-depth analyses have been carried out for all over India as well as for five temperature homogenous regions of India separately. First, the temporal variations of annual and seasonal Tmax and Tmin are analyzed, employing the trend free pre-whitening Mann-Kendall approach. Secondly, it is assessed whether the observations contain significant signals above the natural internal variability determined from a long ‘piControl’ experiment, using Monte Carlo simulation. Thirdly, fingerprint based formal detection and attribution analysis is used to determine the signal strengths of observed and model simulations with respect to different considered experiments. Finally, these signal strengths are compared to attribute the observed changes in Tmax and Tmin to different factors. All the model simulated datasets are retrieved from the CMIP5 archive. It is noticed that the emergence of observed trends is more pronounced in Tmin compared to Tmax. Although observed changes are not solely associated with one specific causative factor, most of the changes in Tmin lie above the bounds of natural internal climate variability.
Remote sensing and GIS based assessment of soil erosion and soil loss risk around hill top surface mines situated in Saranda Forest, Jharkhand
Authors: Kisan Mali Vijay , Khanindra Pathak , Narayan Tiwari Kamlesh , Kumar Tripathy Swarup
Published: December 2015

The quantitative analysis of soil erosion changes over 7 years due to mining operations in two neighboring hilltops in West-Singhbhum District, Jharkhand, are reported. CartoSat-1, ETM+ and LISS-IV satellites' data provided spatial inputs in Universal Soil Loss Equation (USLE) and Morgan, Morgan and Finney method (MMF) models, which were used to predict the average annual soil erosion during the period of 2001–2008 in a geographic information system (GIS), in six distinct classes. In the comparative analysis of the 7-year period, the MMF model revealed a lower coefficient of variation 0.71 (2001) and 0.84 (2008) in predicted average annual soil loss, which increased by 16% (81.3–94.2 t ha−1yr−1), whereas in the case of USLE, the coefficients of variation were 3.88 (2001) and 1.94 (2008), with an increase of 61% (48.56–78.38 t ha−1yr−1). The correlation coefficient of these models was 0.1 (2001) and 0.36 (2008), which shows that both models predicted significantly differently as a result of the different factors considered. Overall, the MMF model predicted a higher soil erosion rate but less variation than USLE. Both models showed soil erosion rates were drastically increased by anthropogenic activities in the area, hence careful consideration is needed. The same sensor and imaging data could not be maintained. Correction of errors may reduce erosion, but it will still remain significant for future planning.