Surface runoff processes and sustainable utilization of water resources in Manas River Basin, Xinjiang, China

Water is the important resource to guarantee the existence and development of oases in arid areas. To improve the utilization efficiency of water resources in Manas River Basin, this paper investigated the trends and periods of runoff based on the runoff and climate data for the past 50 years. Subsequently, with the socioeconomic and water resources data, we studied a comprehensive evaluation on the water security in this area. The results indicated that the stream flows in the three hydrological stations of Hongshanzui, Kensiwat and Bajiahu have sig- nificantly increased and undergone abrupt changes, with periods of 18 and 20 years. According to assessment, water security in the Manas River Basin was at an unsafe level in 2008. In criterion layer, the ecological security index and the index of supply-demand situation are both at the relatively secure level; the quantity index and so- cioeconomic index of water resources are at the unsafe level and basic security level, respectively. Therefore, in order to achieve sustainable economic and social development within the Manas River Basin, it is vital to take a series of effective measures to improve the status of water security.

The complex nonlinear systems with fractal as well as chaotic dynamics of annual runoff processes in the three headwaters of the Tarim River

This paper attempted to identify fractal and chaotic characteristics of the annual runoff processes in headwaters of the Tarim River.Methods of fractal analyses were used to explore several aspects of the temporal changes from 1957 to 2002.The main findings are as follows:(1) The annual runoff processes of the three headwaters of the Tarim River are com-plex nonlinear systems with fractal as well as chaotic dynamics.(2) The correlation dimensions of attractor derived from the time series of the annual runoff for the Hotan,Yarkand and Aksu rivers are all greater than 3.0 and non-integral,implying that all three rivers are chaotic dynamical systems that are sensitive to initial conditions,and the dynamic modeling of their annual runoff process requires at least four independent variables.(3) The time series of annual runoff in each river presents a long-term correlation characteristic.The Hurst exponent for the period of 1989 to 2002 suggests that we may expect to see an increasing trend in the annual runoff of the Aksu and Yarkand rivers in the years after 2002,but a decreasing tendency for the Hotan River in the same period.

Prediction of Debris Flow Runoff Process Based on Hydrological Model： a Case Study at Shenxi Gully,Regarding a Long-Term Impact by Wenchuan Earthquake

Debris flow runoff process is one of key parameters for the design of emergency measures and control engineering. The Shenxi gully in Dujiangyan region,located in the meizoseismal areas of Wenchuan earthquake,was selected as the study area. Based on the research of hazard inducing environment,a soil conservation service( SCS) hydrological model was used to simulate the process of water flow,and then the debris flow runoff process was calculated using the empirical formula combining the results from the SCS hydrological model. Taking the debris flow event occurred on July 9th,2013 as an example,the peak discharges of water flow and debris flow were calculated as 162. 12 and 689. 22 m3/s,with error of 6. 03% compared to the measured values. The debris flow confluence process lasted 1. 8h, which was similar with the actual result. The proposed methodology can be applied to predict the debris flow runoff process in quake-hit areas of the Wenchuan earthquake and is of great importance for debris flow mitigation.

Glacier meltwater runoff process analysis using δD and δ^(18)O isotope and chemistry at the remote Laohugou glacier basin in western Qilian Mountains, China

Stable hydrogen and oxygen isotope has important implication on water and mois- ture transportation tracing research. Based on stable hydrogen （6D） and oxygen （6180） isotope using a Picarro Ll102-i and water chemistry （e.g. major ions, pH, EC and TDS） meas- urement, this study discussed the temporal variation and characteristics of stable hydrogen and oxygen isotope, chemistry （e.g. TDS, pH, EC, Ca^2^, Mg2＋, Na^＋ and CI） in various water bodies including glacier meltwater runoff, ice and snow, and precipitation at the Laohugou g^acier basin during June 2012 to September 2013. Results showed that 6D and δ18O in the meltwater runoff varied obviously with the temporal change from June to September, showing firstly increasing trend and then decreasing trend, with the highest values in July with high air temperature and strong glacier melting, which could indicate the temporal change of glacier melting process and extent. Variations of 6D and δ18O in the runoff were similar with that of snow and ice on the glacier, and the values were also above the GMWL, which probably im- plied that the glacier runoff was mainly originated from glacier melting and precipitation supply The glacier meltwater chemical type at the Laohugou glacier basin were mainly composed by Ca-Na-HCO3-SO4 and Ca-Mg-HCO3-SO4, which also varied evidently with the glacier melting process in summer. By analyzing the temporal change of stable hydrogen and oxygen isotope and chemistry in the melting period, we find it is easy to separate the components of the snow and ice, atmospheric precipitation and melt-runoff in the river, which could reflect the change process of glacier melting during the melting period, and thus this work can contribute to the glacier runoff change study of large-scale region by stable isotope and geochemical method in future.

Effect of Planting Eucalyptus Trees on Runoff Depth and Its Processes of Forestland Natural Watersheds

The runoff and runoff process of Eucalyptus plantations natural watershed were studied to provide guidance for scientific evaluation of water conservation capacities of Eucalyptus plantations,compared with the Pinus massoniana forest natural watershed. The runoff volumes of Eucalyptus plantations and P. massoniana forest natural watersheds were continuously monitored using the small watershed runoff monitoring method and the automatic data collection devices from August,2013 to December,2016,and effects of heavy rainfall and continuous rainfall on the runoff process were studied. Results showed that the annual runoff coefficient of Eucalyptus plantations natural watershed was 0. 050,and 55. 4% lower than P. massoniana forest（ 0. 112）,with the difference being significant（ P 〈 0. 01）. Total runoff duration,time of maximum runoff lagging behind rainfall peak,and runoff duration caused by a heavy rainfall process（ amounting to 147. 5 mm） between the two kinds of forest watersheds were significant different,those of Eucalyptus plantations were 35. 6 mm,0. 2 h and 13. 8 h,respectively,while those of P. massoniana forest were28. 5 mm,0. 7 h and 35. 5 h,respectively. Eucalyptus plantations natural watershed produced only 4-days runoff,and runoff depth amounted to3. 8 mm with a 7-days continuous precipitation process of rainfall with 125. 0 mm,while P. massoniana forest natural watershed produced continuously 13-days runoff,and the runoff depth was 10. 1 mm. In conclusion,water conservation capacity of Eucalyptus plantations is obviously lower than P. massoniana forest.

Hydrological Processes of Storm Runoff from Catchments of Different Land Uses

In this paper, a novel and efficient study on the hydrological processes of storm runoff from catchments of different land uses is conducted. The motivation is to precisely simulate the hydrological processes of storm runoff in the agricultural catchments with different patterns of land uses, i.e., forest, paddy, and upland, respectively. As it is discussed in this paper, different land use leads to different characteristics of storm runoff. In order to understand the changes in the hydrological processes of storm runoff from catchments of different land uses, the effects of rainfall intensity, initial soil moisture deficit, evapotranspiration rate, percolation rate, and retention capacity on hydrological processes of the catchments are taken into consideration. According to the principle of water balance, a general model to connect the separate hydrological processes is developed; then, the individual hydrological process is studied in detail： Firstly, the daily evaporation is calculated according to the relation between the actual evapotranspiration and the potential evapotranspiration rate; Secondly, the retention of storm runoff is plotted against the total rainfall, and the maximum storage is calculated; Thirdly, the percolation rate is calculated for each catchment.

Simulation Experimental Study on Hydrodynamics Process of Erosion and Sediment by Runoff in Grassland

[Objective]The aim was to study the simulation test of hydrodynamics process of erosion.[Method]Through the runoff scouring experiment,the property of soil erosion in Damaoqi grassland in Inner Mongolia was studied.The process and mechanism of soil erosion were studied.[Result]The results of runoff scouring experiment on inner Damaoqi steppe showed that the mean flow velocity of change slope increased with the discharge of flow and slope gradient.The mean silt content rate,the mean sediment transport rate and the mean sheer stress all increased when the discharge of flow increased,which changed in parabolic form with the increase of slope gradient and the critical gradient is 25°.The relationship between the mean sediment transport rate and the mean sheer stress was linear.[Conclusion]The study provided theoretic basis for the report of soil erosion in grassland in China.

Topographic controls on the annual runoff coefficient and implications for landscape evolution across semiarid Qilian Mountains, NE Tibetan Plateau

The combination of different topographic and climatic conditions results in varied precipitation-runoff relations, which in turn influences hillslope erosion, sediment transport and bedrock incision across mountainous landscapes. The runoff coefficient is a suitable tool to represent precipitation-runoff relations, but the spatial distribution of the runoff coefficient across tectonically active mountains in semi-arid environments has received little attention because of limited data availability. We calculated annual runoff coefficients over 22 years for 26 drainage basins across the semi-arid Qilian Mountains based on:(i) annual discharge records;and(ii) the China Meteorological Forcing Dataset to enhance our understanding of the precipitation-runoff processes. The mean annual runoff coefficients show no obvious spatial trends. When compared to potential controlling factors, mean annual runoff coefficients are highly correlated with mean slope rather than any climatic characteristics(e.g., mean annualprecipitation and Normalized Difference Vegetation Index). The slope-dependent runoff coefficient could theoretically have enhanced the topographic control on erosion rates and dampen the influence of precipitation. The enhanced discharge for drainage basins with less precipitation but steep topography in the western Qilian Mountains will enable fluvial incision to keep pace with ongoing uplift caused by the northward growth of the Qilian Mountains. The geomorphic implications are that tectonic rather than climatic factors are more significant for long-term landscape evolution in arid and semi-arid contexts.

Hillslope soil erosion and runoff model for natural rainfall events

By using the momentum theorem and waterbalance principle, basic equations of slope runoff were derived, soil erosion by raindrop splash and runoff were discussed and a model was established for decribing hillslope soil erosion processes. The numerical solution of the model was obtained by adopting the Preissmann format and considering the common solution-determining conditions, from which not only the runoff and soil erosion but also their processes can be described. The model was validated by ten groups of observation data of Soil Conservation Ecological Science and Technology Demonstration Park of Jiangxi Province. Comparisons show that the maximum relative error between simulation and experimental data is about 10.98% for total runoff and 15 % for total erosion, 5.2% for runoffprocess and 6.1% for erosion process, indicating that the model is conceptually realistic and reliable and offers a feasible approach for further studies on the soil erosion process.

The characteristics of rill development and their effects on runoff and sediment yield under different slope gradients

Rill formation is the predominant erosion process in slope land in the Loess Plateau, China. This study was conducted to investigate rill erosion characteristics and their effects on runoff and sediment yielding processes under different slope gradients at a rate of 10°, 15°, 20° and 25° with rainfall intensity of 1.5 mm min-1 in a laboratory setting. Results revealed that mean rill depth and rill density has a positive interrelation to the slope gradient. To the contrary, width-depth ratio and distance of the longest rill to the top of the slope negatively related to slope gradient. All these suggested that increasing slope steepness could enhance rill headward erosion, vertical erosion and the fragmentation of the slope surface. Furthermore,total erosion tended to approach a stable maximum value with increasing slope, which implied that there is probably a threshold slope gradient where soil erosion begins to weaken. At the same time, the correlation analysis showed that there was a close connection between slope gradient and the variousindices of soil erosion: the correlation coefficients of slope gradient with maximal rill depth, number of rills and the distance of the longest rill from the top of the slope were 0.98, 0.97 and-0.98, respectively,indicating that slope gradient is the major factor of affecting the development of rills. Furthermore,runoff was not sensitive to slope gradient and rill formation in this study. Sediment concentration,however, is positively related to slope gradient and rill formation, the sediment concentrations increased rapidly after rill initiation, especially. These results may be essential for soil loss prediction.

Simulation of hydrological processes of mountainous watersheds in inland river basins: taking the Heihe Mainstream River as an example

The hydrological processes of mountainous watersheds in inland river basins are complicated.It is absolutely significant to quantify mountainous runoff for social,economic and ecological purposes.This paper takes the mountainous watershed of the Heihe Mainstream River as a study area to simulate the hydrological processes of mountainous watersheds in inland river basins by using the soil and water assessment tool(SWAT)model.SWAT simulation results show that both the Nash–Sutcliffe efficiency and the determination coefficient values of the calibration period(January 1995 to December 2002)and validation period(January 2002 to December 2009)are higher than 0.90,and the percent bias is controlled within±5%,indicating that the simulation results are satisfactory.According to the SWAT performance,we discussed the yearly and monthly variation trends of the mountainous runoff and the runoff components.The results show that from 1996 to 2009,an indistinctive rising trend was observed for the yearly mountainous runoff,which is mainly recharged by lateral flow,and followed by shallow groundwater runoff and surface runoff.The monthly variation demonstrates that the mountainous runoff decreases slightly from May to July,contrary to other months.The mountainous runoff is mainly recharged by shallow groundwater runoff in January,February,and from October to December,by surface runoff in March and April,and by lateral flow from May to September.

Slope runoff study in situ using rainfall simulator in mountainous area of North China

Simulated rainfall is a valid tool to examine the runoff generation on the slope.13 simulated rainfall experiments with different rainfall intensities and durations are completed in a 5 m ×10 m experimental plot in mountainous area of North China.Simultaneously,rainfall,surface runoff,soil-layer flow,mantel-layer flow and soil moisture are monitored respectively.From the results,it is found that the hydrographs in all layers have the characteristics of rapid rise and fall.The recessions of surface flow and soil-layer flow are much faster than that of mantel-layer flow.Surface flow,the main contributor,makes up more than 60% of the total runoff in the study area.It even exceeds 90% in the cases of high intensity rainfall events.Runoff coefficient(ratio of total runoff to rainfall amount) is mainly influenced by rainfall amount,rainfall intensity and antecedent soil moisture,and the relationship can be well expressed by a multiple linear regression function α = 0.002P + 0.182i + 4.88Wa-0.821.The relation between the rainfall intensity and the lag time of three flows(surface runoff,soil-layer flow and mantel-layer flow) is shown to be exponential.Then,the result also shows that the recession constant is 0.75 for surface runoff,is 0.94 for soil-layer and mantel-layer flow in this area.In this study area,the dominant infiltration excess runoff is simulated by Horton model.About 0.10 mm/min percolation is observed under the condition of different rainfall intensities,therefore the value is regarded as the steady infiltration rate of the study area.

Effects of urban grass coverage on rainfall-induced runoff in Xi'an loess region in China

In this study, laboratory rainfall simulation experiments were conducted to investigate the regulatory effects of grass coverage on rainfallrunoff processes. A total of 80 grass blocks planted with well-grown manilagrass, together with their root systems, were sampled from an eastern suburban area of Xi'an City in the northwest arid area of China and sent to a laboratory for rainfall simulation experiments. The runoff and infiltration processes of a slope with different grass coverage ratios and vegetation patterns were analyzed. The results show that the runoff coefficient decreases with the increase of the grass coverage ratio, and the influence of grass coverage on the reduction of runoff shows a high degree of spatial variation. At a constant grass coverage ratio, as the area of grass coverage moves downward, the runoff coefficient, total runoff,and flood peak discharge gradually decrease, and the flood peak occurs later. With the increase of the grass coverage ratio, the flood peak discharge gradually decreases, and the flood peak occurs later as well. In conclusion, a high grass coverage ratio with the area of grass coverage located at the lower part of the slope will lead to satisfactory regulatory effects on rainfall-induced runoff.

Simulation of Runoff and Sediment Yield for a Himalayan Watershed Using SWAT Model

Watershed is considered to be the ideal unit for management of the natural resources. Extraction of water-shed parameters using Remote Sensing and Geographical Information System (GIS) and use of mathematical models is the current trend for hydrologic evaluation of watersheds. The Soil and Water Assessment Tool (SWAT) having an interface with ArcView GIS software (AVSWAT2000/X) was selected for the estimation of runoff and sediment yield from an area of Suni to Kasol, an intermediate watershed of Satluj river, located in Western Himalayan region. The model was calibrated for the years 1993 & 1994 and validated with the observed runoff and sediment yield for the years 1995, 1996 and 1997. The performance of the model was evaluated using statistical and graphical methods to assess the capability of the model in simulating the run-off and sediment yield from the study area. The coefficient of determination (R2) for the daily and monthly runoff was obtained as 0.53 and 0.90 respectively for the calibration period and 0.33 and 0.62 respectively for the validation period. The R2 value in estimating the daily and monthly sediment yield during calibration was computed as 0.33 and 0.38 respectively. The R2 for daily and monthly sediment yield values for 1995 to 1997 was observed to be 0.26 and 0.47.

Artificial Neural Networks for Event Based Rainfall-Runoff Modeling

The Artificial Neural Network (ANN) approach has been successfully used in many hydrological studies especially the rainfall-runoff modeling using continuous data. The present study examines its applicability to model the event-based rainfall-runoff process. A case study has been done for Ajay river basin to develop event-based rainfall-runoff model for the basin to simulate the hourly runoff at Sarath gauging site. The results demonstrate that ANN models are able to provide a good representation of an event-based rainfall-runoff process. The two important parameters, when predicting a flood hydrograph, are the magnitude of the peak discharge and the time to peak discharge. The developed ANN models have been able to predict this information with great accuracy. This shows that ANNs can be very efficient in modeling an event-based rainfall-runoff process for determining the peak discharge and time to the peak discharge very accurately. This is important in water resources design and management applications, where peak discharge and time to peak discharge are important input

Runoff separation and eco-hydrological function in the typical landscape zones combining hydrochemical and isotopic tracers:a review

The study on the coupling relationship and hydrology mechanism between ecosystem and hydrological process in a basin has recently become the international research frontier in hydrology.Runoff separation is still an important subject and possibly cutting edge process in hydrology.This paper summarizes the progress of national and international research,and comments on the advantages and disadvantages of recent,diverse base flow separation methods.This paper also presents research on hydrological process and eco-hydrological function in different landscape zones,combining isotopic technology with hydrochemical methods.Based on the runoff separation of different water bodies,this paper probes into the coupling relationship and hydrology mechanism between ecosystem pattern and eco-hydrological process,and makes analysis on water conservation,regulation and storage mechanism,and eco-hydrological function in different landscape zones.This report also examines future trends in research on hydrological process and eco-hydrological function in mountainous areas.

梁子湖流域降雨径流过程及氮磷流失对不同景观格局的响应

景观格局决定小流域能源流动与水沙过程,是影响氮磷流失的重要因素。以湖北梁子湖流域的双溪(农林复合型)和石桥(林地型)2个典型小流域为研究对象,在自然降雨条件下,于2016年1-12月对流域出口断面水质水量进行了连续监测,并结合丰水期典型次降雨径流过程,探讨了不同景观格局下小流域降雨径流过程和氮磷输出特征,为梁子湖环境综合治理提供一定的科学依据。结果表明:(1)降雨径流过程在不同景观格局小流域内呈现出明显差异。相比于双溪小流域,石桥小流域产流能力较强,径流过程呈现出汇流时间较短、径流响应速度较快、径流模数较大的趋势;(2)双溪小流域总氮(TN)和总磷(TP)月均输出浓度范围分别为1.29~4.28 mg/L和0.04~0.22 mg/L,均高于石桥小流域(TN:0.62~1.90 mg/L;TP:0.02~0.11 mg/L),其中硝态氮(NO_(3)^(-)-N)是氮素流失的主要形态,占TN流失的51.8%~88.2%。相比于石桥小流域,双溪小流域的NO_(3)^(-)-N/TN较大。2个小流域的氨氮(NH_(4)^(+)-N)和亚硝态氮(NO_(2)^(-)-N)输出浓度均较低并且无明显变化趋势;(3)双溪小流域的TN和TP月均输出通量范围分别为1.83~20.03 g/s和0.04~1.45 g/s,均高于石桥小流域(TN:0.62~10.01 g/s;TP:0.01~0.54 g/s),且与同时段流量呈现显著正相关关系(P<0.01);(4)双溪小流域的TN和TP流失强度分别为3.68和0.20 t/(km^(2)·a),分别是石桥小流域的1.32倍和1.30倍。氮磷流失主要集中在降雨频繁的4-7月,占全年流失负荷的70%以上。综上,梁子湖流域景观格局显著影响养分流失,优化土地利用配置和科学合理施肥是改善该流域水环境的科学措施。

小区尺度雨洪过程模拟及径流分配特性研究

为了研究小区尺度地表径流各组分占比随不同重现期降雨的变化规律,以西咸新区天福和园小区为研究对象,采用GAST-SWMM耦合模型,以模拟时长及地形边界条件为变量进行研究分析。研究表明:经两场实测降雨过程验证,模型确定性系数分别为0.83和0.82,表明构建的一二维耦合模型精度较高;在本文设置的两种工况下,小区地表径流外排率和管网排水率均随降雨重现期增大而以渐进曲线形式增大,土壤下渗占比和地表填洼率随降雨重现期增大而减小;小区地表径流外排和管网排水主要发生在降雨期间,分别占各自排水总量的94.88%和94.36%;小区地形边界条件对径流过程模拟的影响不容忽视,在有围墙及无围墙工况下平均地表径流外排率分别为9.42%、22.55%。本研究可为地势相对四周较低区域的排水防涝设计提供参考。

Simulation on the Time Progress of the Non-Point Source Pollution Load in Initial Stage Runoff for Small Watershed

Taking a reservoir in South China as an example, we use rainfall-runoff unit hydrograph method to analyze the time changing process of surface runoff inflow, which generated by typical design rainfall. On the basis of time series data of flow and water quality in control section of the main rivers in Xili Reservoir, we establish mathematical response relation between non-point source pollutants flux, such as flux of COD, flux of NH3-H, in catchment area of control section and runoff. Then we simulate the time dynamic change progress of non-point source pollution load which generate with the initial stage runoff that generated by design rainfall and flow into reservoir. It can provide technical parameters for the design of non-point source which generate from early runoff treatment project.

基于雨洪过程模拟与海绵体建设适宜性评价的城市适应性规划方法——以长汀县汀江上游流域为例

统筹考虑流域海绵体的空间布局及其与雨洪过程的功能耦合关系是解决城市雨洪灾害问题的重要途径。以长汀县汀江上游流域为例,分别使用SWAT和SCS模型模拟雨洪径流和淹没过程,利用InVSET模型评价海绵体建设适宜性,进而对二者的相互关系进行深入研究,提出基于雨洪过程模拟和海绵体建设适宜性评价的城市适应性规划方法。结果表明:(1)构建的汀江上游流域SWAT和SCS模型可以准确识别出研究区的雨洪产流区、汇流廊道、汇流节点和淹没区域,并反映其空间分布特征;基于InVEST模型结合雨洪调蓄、水源涵养、土壤保持和水质净化等指标实现了定量刻画海绵体建设适宜性的目标,集成雨洪过程模拟与海绵体建设适宜性评价为重构流域海绵系统空间格局提供了一种新的方法。(2)长汀县中心城区低雨洪安全格局面积占其安全格局总面积的37.51%,呈现出沿河道集中分布的特点,使中心城区面临较大的雨洪风险;海绵体建设适宜区域呈现出不均匀分布的特征,高适宜区域占流域总面积的7.91%,集中分布在中心城区北面的大片农田中。通过优化研究区海绵空间格局,并依据地块使用性质设定差异化的管控目标,实现减缓研究区雨洪风险的目标,为海绵城市规划实践提供参考依据。