Effect of climate change and land use on stream flow in the upper and middle reaches of the Taoer River,northeastern China

The upper and middle reaches of the Taoer River, a representative ecologically sensitive area, has experienced great climate change and rapid agricultural and industrial development since 1961. There is therefore an urgent need to evaluate the impact of climate change and human activities on stream flows to serve better the water resource management in this region. The nonparamet- ric Mann-Kendall test and moving t-test were used to identify trends and change points in stream flow, precipitation and potential evapotranspiration data series. A significant upward trend has been found in annual stream flow, with an abrupt change identified in 1985 at the Taonan station which is the station that controls the entire study area. The stream flow data was divided into a baseline period and a period of change. Both Fu and Zhang＇s functions were employed to evaluate the impacts of variation in climate and human activities on mean annual stream flow, based on precipitation and potential evaporation. Analysis of the increase in mean annual stream flow between the baseline and the period of change indicated that climate change accounted for about 45% of the total increase and human activities were responsible for about 55%.

Non-Aligned Stagnation Point Flow of a Casson Fluid Past a Stretching Sheet in a Doubly Stratified Medium

This paper investigates the problem of oblique hydro magnetic stagnation point flow of an electrically conducting Casson fluid over stretching sheet embedded in a doubly stratified medium in the presence of thermal radiation and heat source/absorption with first order chemical reaction.It is assumed that the fluid impinges on the wall obliquely.Similarity variables were used to convert the partial differential equations to ordinary differential equations.The transformed ordinary differential equations are solved numerically using Runge-Kutta-Fehlberg method with shooting technique.It is observed that a boundary layer is formed when the stretching velocity of the surface is less than the in viscid free stream velocity at a point decreases with increase in the non-Newtonian rheology parameter.The augmentation of the temperature is observed with the magnetic parameter,heat source parameter and thermal radiation parameter while a reverse effect with thermal stratification number,Prandtl number and the velocity ratio parameter.Influence of Skin friction coefficient,Nusselt number and Sherwood number on the flow configurations for different values of pertinent parameters are portrayed graphically and discussed.Numerical results are compared with the published results and are found to be in good agreement with previously published results as special cases of present problem.The mass concentration is seen to be decrease with Schmidt number,chemical reaction parameter and solutal stratification number.

The asymptotic solution of particle growth in the convective undercooled melt driven by a biaxial straining flow

A dynamical system of particle growth in the con vective undercooled melt driven by a biaxial straining flow is modeled. A uniformly valid asymptotic solution for the in terface evolution in particle growth is obtained by means of the multiple variable expansion method. The analytical so lution as a function of both azimuth angle and polar angle shows that the interface shape of particle growth in the bi axial straining flow is significantly deformed by the biaxial straining flow. The biaxial straining flow results in higher lo cal growth rate near the surface where the flow comes in and leads to lower local growth rate near the surface where the flow goes out. Due to the difference in local growth rate, an initially spherical particle will evolve into a prolate barrel like shape in the biaxial straining flow.

Influence of Tea Plantations, Forest and Mixed Farming on Stream Flow and Sediment Loads, Case of Sondu Miriu River Basin, Kenya

The changing patterns of land cover and land use in the tropical river basin over time are critical. The hydrological phenomena at basin and sub basin scale are affected positively or negatively by dynamics of the land cover and land use patterns. Hence identifying causes and driving factors aid in taking appropriate measures to avert the impacts. This study determined the influences of sub basins dominated by tea plantations, forests and agricultural land uses in terms of streamflow and sediment flux variability in Sondu Miriu River Basin in Kenya, East Africa. Field-based investigations were conducted through sampling of flow velocities, turbidity and TSSC obtained from existing River Gauging Stations established within the three sub basins. The sub basin dominated by mixed farming land cover exhibits high turbidity approximately 620 NTU and high levels of total suspended sediment concentration (TSSC) of the order of 630 mg/l in wet seasons. The turbidity levels and TSSC were low in sub basins dominated by forest and tea plantations with approximately mean value of 17 - 29 NTU and 0.019 g/l. The sediment loads in sub basin dominated by mixed farming in the pre planting season in January to February were about 900 tonnes/day higher than that in crop growing season. In sub basins dominated by forest cover and tea plantations, sediment loads were low ranging between 2 - 7 tonnes/day. The relationship between stream flows and area under tea plantations, forests and mixed farming ranged between R2 of 0.025 and 0.16. Tea plantations and forests influence the stream flows and sediment yields in long term duration while in mixed farming variations were observed seasonally. The strong relationships between rainfall and stream flows at the sub basins ranging between R2 of 0.84 and 0.97 revealed the significance of rainfall in hydrologic response of the Sondu Miriu River Basin.

Impacts of Global Warming Perturbation on Water Resources in Arid Zone: Case Study of Kaidu River Basin in Northwest China

The main goal of this study was to assess the long-term impacts of global warming perturbation on water resources of the Kaidu River Basin in Northwest China. Temperature, precipitation and hydrology data during the past 29 years from 1979 to 2007 were collected and analyzed using parametric and non-parametric methods, the connection between temperature and precipitation by the combination of grey correlation analysis method and the hypothesis testing for trend of climate change. The results show a high increase in temperature in the study area as well as an extreme and highly variable hydrological regime in this region, where flash floods can exceed the total runoff from a sequence of years. These variations may be due to the geographical location of the Kaidu River Basin in arid zone. It also reveals that precipitation has a much greater impact on stream flow than that of temperature. The development of new approaches was proposed as responses to climate change in this arid region.

Numerical Simulation of Dam-Break Flooding of Cascade Reservoirs

Previous studies at home and abroad have mainly focused on single dam-break, and little attention has been paid so far to the dam-break of cascade reservoirs. Multi-source flooding, which can lead to three-dimensional turbulent phenomena and superposition effects, is the main difference between the dam-break of cascade and single reservoirs. Detailed descriptions of the coupled numerical simulation of multi-source flooding have little been reported, and the initial wet riverbed is rarely considered in current models. Therefore, in this paper, a method based on the three-dimensional (Formula presented.) turbulence model coupled with the volume-of-fluid method is proposed to simulate the dam-break flooding of cascade reservoirs. The upstream river, reservoir, and downstream river are connected by the internal boundary method, and the initial conditions, including river flow and reservoir water, are determined according to the results of the numerical simulation. Coupled numerical simulation of different dam-break flooding is then achieved. The present work solves the challenges presented by the enhancement and superposition of natural river flow, upstream flooding, and downstream flooding. This paper provides a theoretical basis for future studies on the dam-break flood routing of cascade reservoirs. © 2017 Tianjin University and Springer-Verlag GmbH Germany

Integrating water use systems and soil and water conservation measures into a hydrological model of an Iranian Wadi system

Water resources are precious in arid and semi-arid areas such as the Wadis of Iran. To sustainably manage these limited water resources, the residents of the Iranian Wadis have been traditionally using several water use systems(WUSs) which affect natural hydrological processes. In this study, WUSs and soil and water conservation measures(SWCMs) were integrated in a hydrological model of the Halilrood Basin in Iran. The Soil and Water Assessment Tool(SWAT) model was used to simulate the hydrological processes between 1993 and 2009 at daily time scale. To assess the importance of WUSs and SWCMs, we compared a model setup without WUSs and SWCMs(Default model) with a model setup with WUSs and SWCMs(WUS-SWCM model). When compared to the observed daily stream flow, the number of acceptable calibration runs as defined by the performance thresholds(Nash-Sutcliffe efficiency(NSE)≥0.68, –25%≤percent bias(PBIAS)≤25% and ratio of standard deviation(RSR)≤0.56) is 177 for the Default model and 1945 for the WUS-SWCM model. Also, the average Kling–Gupta efficiency(KGE) of acceptable calibration runs for the WUS-SWCM model is higher in both calibration and validation periods. When WUSs and SWCMs are implemented, surface runoff(between 30% and 99%) and water yield(between 0 and 18%) decreased in all sub-basins. Moreover, SWCMs lead to a higher contribution of groundwater flow to the channel and compensate for the extracted water by WUSs from the shallow aquifer. In summary, implementing WUSs and SWCMs in the SWAT model enhances model plausibility significantly.

Passive ranging technique using waveguide invariant in shallow water with thermocline

Waveguide invariant is widely used in underwater target passive ranging. In shallow water with uniform sound speed profile, the value of waveguide invariant is approximately a constant, while in shallow water with thermocline, it varies in a wide range. The waveguide invariant distributions and striations in these two conditions are analyzed respectively. On the basis of wavenumber difference between reflected modes and refracted modes, a wavenumber-frequency domain filtering technique is proposed to separate the two groups of modes. The required relationship between array element space, total array length and target azimuth for effective application is discussed. Finally, the simulation results indicate that in shallow water with a thermocline, refracted modes can be effectively filtered out using the wavenumber-frequency domain filtering technique and the target's range is estimated accurately. © 2017 Beijing Institute of Aerospace Information.

Extenuating the parameters using HEC-HMS hydrological model for ungauged catchment in the central Omo-Gibe Basin of Ethiopia

Characteristics of ungauged catchments can be studied from the hydrological model parameters of gauged catchments.In this research,discharge prediction was carried out in ungauged catchments using HEC-HMS in the central Omo-Gibe basin.Linear regression,spatial proximity,area ratio,and sub-basin mean were amalgamated for regionalization.The regional model parameters of the gauged catchment and physical characteristics of ungauged catchments were collated together to develop the equations to predict discharge from ungauged catchments.From the sensitivity analysis,crop coefficient(CC),storage coefficient(R),constant rate(CR),and time of concentration(TC)are found to be more sensitive than others.The model efficiency was evaluated using Nash-Sutcliffe Efficiency(N_(SE))which was greater than 0.75,varying between−10%and+10%and the coefficient of determination(R^(2))was approximated to be 0.8 during the calibration and validation period.The model parameters in ungauged catchments were determined using the regional model(linear regression),sub-basin mean,area ratio,and spatial proximity methods,and the discharge was simulated using the HEC-HMS model.Linear regression was used in the prediction where p-value≤0.1,determination coefficient(R2)=0.91 for crop coefficient(CC)and 0.99 for maximum deficit(MD).Constant rate(CR),maximum storage(MS),initial storage(IS),storage coefficient(R),and time of concentration(TC)were obtained.The result is that an average of 30 m^(3)/s and 15 m^(3)/s as the maximum monthly simulated flow for ungauged sub-catchments,i.e.Denchiya and Mansa of the main river basin.

A UNIFORMLY VALID ASYMPTOTIC SOLUTION OF THE NAVIER-STOKES EQUATIONS

In this paper, problems of the flow over a fat plate in the large Reynolds numbercase are studied by using the method of multiple scales￣[1,2].We have obtained N-orderuniformly valid asymptotic solutions of the Naver-Stodes equations.

Software Defined Traffic Engineering for Improving Quality of Service

The Software Defined Networking(SDN) paradigm separates the control plane from the packet forwarding plane, and provides applications with a centralized view of the distributed network state. Thanks to the flexibility and efficiency of the traffic flow management, SDN based traffic engineering increases network utilization and improves Quality of Service(QoS). In this paper, an SDN based traffic scheduling algorithm called CATS is proposed to detect and control congestions in real time. In particular, a new concept of aggregated elephant flow is presented. And then a traffic scheduling optimization model is formulated with the goal of minimizing the variance of link utilization and improving QoS. We develop a chaos genetic algorithm to solve this NP-hard problem. At the end of this paper, we use Mininet, Floodlight and video traces to simulate the SDN enabled video networking. We simulate both the case of live video streaming in the wide area backbone network and the case of video file transferring among data centers. Simulation results show that the proposed algorithm CATS effectively eliminates network congestions in subsecond. In consequence, CATS improves the QoS with lower packet loss rate and balanced link utilization.

The effect of reforestation on stream flow in Upper Nan river basin using Soil and Water Assessment Tool(SWAT)model

Forests are an important natural resource,vital to all life.Forests are an important source of food,clothing,and medicines,as well as a place to live.Water released from forests drains into the soil causing groundwater to emerge as stream flow throughout the year.In Thailand,most forests have been encroached by logging,paper production,and housing construction.Population growth and the need for farming area for crop and livestock production have also caused forest encroachment.Technical tools are needed to support the decision makers and planners if they are to achieve objectives of water conservation,and development.These technical tools are needed for assistance in the engineering,socio-economic,and environmental planning.The Soil and Water Assessment Tool(SWAT)was used in the hydrological modeling in this study of the complex and dynamic problems of The Upper Nan river basin.This was a case study to evaluate the impact of changing conditions in the river basin affected by the stream flow due to reforestation.The watershed area was delineated into 5 sub-watersheds based on surface topography provided by the Digital Elevation Model(DEM)and the parameters of each of these watersheds were calculated.The land use data was processed and reclassified to match with the SWAT model land use code.Ten different categories of land use in the study area were used for SWAT processing.Types of land use consist of:mixed forest(33.7%),disturbed forest(30.2%),evergreen forest(17.7%),paddy field(7.1%),orchard(3.7%),range brush(2.7%),field crop(1.7%),planted forest(1.7%),urban(1.4%)and water resources(0.4%).Twenty-two types of soil were found in the basin.The initial curve number values were assigned based on the land use type and soil hydrologic group for the average antecedent moisture condition of the curve number method.The potential evapotranspiration was computed using the Penman-Monteith method.The simulation was performed using three reforestation scenarios to assess stream flow:(1)improved disturbed forest,(2)field crops and range grass,and(3)both disturbed forest and field crops.The results of reforestation from scenarios 1 and 3 can increase stream flow in the drought season and can also reduce the flow in the wet season in the main stream and its tributaries.For scenario 2 Reforestation had no significant effect on the main stream.

Influence of climate variability and human activities on stream flow variation in the past 50 years in Taoer River, Northeast China

Taoer River Basin, which is located in the west of Northeast China, is an agropastoral ecotone. In recent years, the hydrological cycle and water resources have changed significantly with the deterioration of the environment. Many water problems such as river blanking, wetland shrinking and salinization have occurred in this region. All of these phenomena were directly caused by changes in stream flow under climate variability and human actiities. In light of the situation, the impact of climate variability and human activities on stream flow should be identified immediately to identify the primary driving factors of basin hydrological processes. To achieve this, statistical tests were applied to identify trends in variation and catastrophe points in mean annual stream flow from 1961 to 2011. A runoff sensitive coefficients method and a SIMHYD model were applied to assess the impacts of stream flow variation. The following conclusions were found： 1 ） The years 1985 and 2000 were confirmed to be catastrophe points in the stream flow series. Thus, the study period could be divided into three periods, from 1961 to 1985 （Period I）, 1986 to 2000 （Period II） and 2001 to 2011 （Period III）. 2） Mean annual observed stream flow was 31.54 mm in Period I, then increased to 65.60 mm in Period II and decreased to 2.92 mm in Period III. 3） Using runoff sensitive coefficients, the contribution of climate variability was 41.93% and 43.14% of the increase in stream flow during Periods II and III, suggesting that the contribution of human activities to the increase was 58.07% and 56.86%, respectively. 4） Climate variability accounted for 42.57% and 44.30% of the decrease in stream flow, while human activities accounted for 57.43% and 55.70% of the decrease, according to the SIMHYD model. 5） In comparison of these two methods, the primary driving factors of stream flow variation could be considered to be human activities, which contributed about 15% more than climate variability. It is hoped that these conclusions will .benefit future regional planning and sustainable development.

STREAMLINE-EQUIVORTICITY-LINE ITERATION METHOD FOR CALCULATING STEADY FLOW OF NONUNIFORM STREAM PAST A CIRCULAR CYLINDER

In this paper, an iteration method is presented to calculate the steady noseparation flow past a circular cylinder with brokenline-shaped velocity profile. At each iteration step, the streamlines of the last step are considered as equivorticity lines to determine the new flow field. The iterative process is stopped when certain convergence criterion is reached. Several examples are given which show the effectiveness of the method.

Effect of land use land cover dynamics on hydrological response of watershed:Case study of Tekeze Dam watershed,northern Ethiopia

Land use change is a very important issue considering global dynamics and their response to hydrologic characteristics of soil and water management in a catchment.A significant land use change has been observed in the Tekeze dam catchment.The main objective of this study was to estimate the potential impacts of the land use land cover(LULC)dynamics on hydrological response(stream flow and sediment yield).This was done by integrating SWAT model with GIS.The simulation and sensitivity analysis for each land use was done by dividing the catchment in to 47 sub-catchments and assigning HRUs based on multiple HRU definition.After a sensitivity analysis,calibration and validation of SWAT model,the impact of LULC dynamics on hydrological response were evaluated with three scenarios(climate of 2000s&2008 LULC,climate of 2000s&1986 LULC and climate of 1980s&1986 LULC).In the Tekeze dam watershed,land cover change had a beneficial impact on modeled watershed response due to the transition from grass and shrub land to agricultural land.Simulation results for the Tekeze dam watershed indicates that increasing bare land and agricultural areas resulted in increased annual and seasonal stream flow and sediment yield in volumes.The mean annual stream flow was increased by 6.02%(129.20-137.74 m^(3)/s)and the impact on sediment yield amounts to an increase of 17.39%(12.54-15.18 t/ha/yr)due to LULC dynamics.The hydrological response was more sensitive to LULC dynamics for the months of August to October than others in the year.These results demonstrate the usefulness of integrating remote sensing and distributed hydrologic models through the use of GIS for assessing watershed conditions and the relative impacts of land cover transitions on hydrologic response in a continuous manner.

Modified Carbothermal Synthesis of TiC Whiskers

A new approach to the massive production of TiC whiskers with high purity and low cost was presented. It is a modified carbothermal reduction method （MCTR） characterized by argon stream flowing vertically and passing through the interior of the mixture of raw materials. It is found for the first time that there is an optimum flow of the upward flowing argon stream, at which large quantity of high quality TiC can be obtained. This paper described the new method, analyzed the mechanism and conditions for the formation of high purity TiC whiskers on a large scale, and compared MCTR with the traditional carbothermal reduction method （TCTR）. Based on the analysis and comparison, it is concluded that in order to produce high quality transition metal carbides, nitrides and carbonitrides with low cost TCTR must be replaced by MCTR.

Channeling the water data deluge:a system for flexible integration and analysis of hydrologic data

The hydrologic cycle and understanding the relationship between rainfall and runoff is an important component of earth system science,sustainable development,and natural disasters caused by floods.With this in mind,the integration of digital earth data for hydrologic sciences is an important area of research.Currently,it takes a tremendous amount of effort to perform hydrologic analysis at a large scale because the data to support such analyses are not available on a single system in an integrated format that can be easily manipulated.Furthermore,the state-of-the-art in hydrologic data integration typically uses a rigid relational database making it difficult to redesign the data model to incorporate new data types.The HydroCloud system incorporates a flexible document data model to integrate precipitation and stream flow data across spatial and temporal dimensions for large-scale hydrologic analyses.In this paper,a document database schema is presented to store the integrated data-set along with analysis tools such as web services for data access and a web interface for exploratory data analysis.The utility of the system is demonstrated based on a scientific workflow that uses the system for both exploratory data analysis and statistical hypothesis testing.