Abstract: The existing methods for watershed zoning have tended to be very subjective in China. This is especially true for the zoning of the water pollution control-unit, resulting from the lack of unified zoning methodologies and regulations.Aiming at this problem, a three-level zoning system or the watershed-control regions-control units system is proposed in the study.The system adopts a combined approach of qualitative and quantitative methods for the zoning study of watershed pollution control.An Analytic Hierarchy Process (AHP) model will be constructed at the control-unit level, which is the central piece of the system.Based on four factors, i.e. catchment characteristics, urban distribution, industrial distribution and agricultural distribution, a watershed is divided into various control units according to the main direction of various discharge sources.The system is applied to the Songhua River watershed as a study case.The whole watershed is ultimately divided into three control regions and thirty-three control-units.It is noted that ten counties including Morin Dawa Daur Autonomous Banner, are divided into two or more control units.The proposed system for the zoning study of watershed pollution control in China is based on the nature of basin catchments and fully embodies the focus and direction for the management of watershed pollution control.It sets up the implementing targets and spells out the responsibilities and missions for local governments.It thus could provide the basis and guarantee for scientifically planning and implementing watershed pollution control plans in China.
Abstract: The multi-scale standardized precipitation and evapotranspiration index (SPEI) is calculated using the monthly precipitation and temperature data observed at 74 meteorological stations during 1962-2007 in Guangdong.The spatial-temporal variation of wet and dry spells is analyzed using the methods of the rotated empirical orthogonal function (REOF), the Mann-Kendall trend test and the wavelet analysis.Results show that both the frequency and spatial extent of drought have increased over time since the 1970s.The whole Guangdong can be divided into six wet and dry regions based on the first six modes of REOF.These regions are located in the Pearl River Delta, the upper Hanjiang River and Dongjiang River basins, the Xijiang River basin and the middle and lower Beijiang River basin, the eastern coastal district, the upper Beijiang River basin, and the western coastal district.The trend of wet and dry spells in Guangdong varies significantly across the province from east to east.Significant upward trends in drought have been detected in the Leizhou Peninsula, the Xijiang River basin and the middle and lower Beijiang River basin, the western coastal district.In addition, the temporal variation of wet and dry spells exhibits a periodic oscillation of period of 2 to 8 years in the six regions.
Abstract: A statistical method is proposed for calculating the frequency of a two-dimensional vector combining of discharge and sediment concentration.The method can be applied to compute the effective sediment-transporting discharge a channel reach.Using the observed discharge and sediment data from the Bayangaole station located in the Inner Mongolia reach of Yellow River during the period 1954-2006, the effective sediment-transporting discharge is calculated annually.The corresponding effective incoming sediment coefficient is also obtained.The relationships between the bank-full discharge and the effective discharge, as well as the effective incoming sediment coefficient are analyzed.The result shows that the current value of bank-full discharge at the Bayangaole station in the Inner Mongolia reach of Yellow River is affected by the antecedent discharge and sediment conditions in the previous 12 years.
Abstract: Snow cover is one of the most active factors that influence the environment, and shows high sensitivity to climate changes.Based on the moderate resolution imaging spectroradiometer (MODIS) snow cover products and observed data from 84 meteorological stations within Xinjiang Uygur Autonomous Region of China, we extracted the snow cover information during the last 10 years in Xinjiang and evaluated the accuracy of MOD10A2 products.The inter-annual and seasonal changes of Snow Cover Fraction (SCF), as well as their difference between Northern Xinjiang and Southern Xinjiang, were also examined.In addition, the spatial-temporal variability of SCF in different elevation zones was obtained for assessing the influence of the elevation shift on SCF.The results indicated that: ① the total accuracy of SCF extracted from MOD10A2 data is 92.3%, and can be considered as a credible data source to detect the snow cover change in Xinjiang; ② during 2000 to 2010, the maximum SCF of Xinjiang is in the range between 34.0% and 51.7% and the minimum is in the range between 1.7% and 2.6%.The difference of SCF between Northern Xinjiang and Southern Xinjiang is obvious: the SCF of Southern Xinjiang is relatively low and the fluctuation of SCF is less than 50%; the SCF of Northern Xinjiang is relatively high because of the effects of complex terrain and climate, and the fluctuation of SCF is more than 80% except in 2008.Seasonally, the averaged SCF show significant fluctuations in spring and autumn, however, the SCF does not show obviously change trend in summers and winters.Moreover, the north part of Xinjiang province shows more significant inter-annual and seasonal change than Southern Xinjiang; ③ the SFC typically reach minimum values in summers and maximum values in winters in the areas where the elevations below 4 000 m, but display a converse pattern in the areas above 6 000 m with a minimum in winters and a maximum in summers.
Abstract: Trend test is an essential topic in climate change research.Three trend test methods, Mann-Kendall, Pre-Whitening Mann-Kendall and Trend-Free Pre-Whitening Mann-Kendall, are employed to analyze trends and autocorrelations of annual precipitation, pan evaporation and average air temperature spatially and temporally across China.The meteorological variables are observed at 317 stations during the period 1956-2005.Specifically, the autocorrelation of annual precipitation is insignificant, resulting in the similar trend analysis results for the three methods.While both annual pan evaporation and average temperature exhibit significant autocorrelations, which result in distinct trend test results using the three methods.Thus, the autocorrelation must be properly considered when conducting a trend test for both annual pan evaporation and average air temperature. In general, meteorological data from northern basins has a more significant autocorrelation than the southern one.In addition, the effects of trend on the estimated autocorrelation coefficient and correlation on the Mann-Kendall statistics are also investigated theoretically.Results indicate that the positive correlation magnifies the series trend significance and the trend existed in the series may contaminate the lag-1 autocorrelation coefficient in turn.
Abstract: To improve the accuracy of real-time flood forecasting, a new effective error correction method based on dynamic system response curve (DSRC) was proposed in this paper.The dynamic system response curve was introduced to construct a dynamic error updating model for correcting the flood forecasting errors.In this study, the water sources separation and watershed concentration modules of the Xin’anjiang model were utilized as a response system.Substituting the linear difference for partial differential values of the response function in a nonlinear system, the system response curves of runoff time series can be obtained.Based on the observed and calculated discharge, the calculated runoff was corrected using the least square estimation, and the discharge hydrograph was recalculated with the corrected runoff.The method was tested in both ideal scenario and real case study.Comparing to the second-order autoregressive error forecast model, the new method can significantly improve the accuracy of real-time flood forecasting.The new method has a simple structure without newly introduced parameters and effective.
Abstract: New multi-site daily discharge simulation method need be developed, because more information is needed accompanying with the rapidly increasing construction of reservoirs.In this study, a new multi-site daily flow simulation model was proposed, in which the daily flow of key gauging station was simulated by an autoregressive model.The copula function was built to describe the temporal and spatial dependence between the key gauging station and others.At last, the daily flows of other sites were obtained using the copulas.The upper Yangtze River was selected as a case study.The daily flow of six sites, including the Yichang in the Yangtze River, Pingshan in the Jinshajiang River, Gaochang in the Minjiang River, Lijiawan in the Tuojiang River, Beibei in the Jialingjiang River and Wulong in the Wujiang River, were simulated.The results indicated that the difference of characteristic values between simulated and observed series were small and the proposed method is superior to the current methods.This study provides a new way for stochastic simulation of multisite daily flows.
Abstract: The objective of this study was to understand the effects of rainfall characteristics and micrometeorology on rainfall redistribution within Chinese red pine (or Pinus tabulaeformis) forest.During growing seasons of 2006-2008, gross rainfall, throughfall, stemflow, and micrometeorology were directly observed from a naturally generated secondary coniferous forest in Qinling Mountains, China.Correlation and multiple regression methods were used to examine the relationships among those measured parameters.Results show that the rainfall class is the most important factor in rainfall partitioning.A positive correlation exists between the dependent variable throughfall and each of the following independent variables including rainfall, the interaction terms of rainfall and rainfall duration, and relative humidity.A negative correlation exists between throughfall and the rainfall duration, also between throughfall and temperature.The stemflow was positively correlated with rainfall, interaction terms of rainfall and temperature, negatively correlated with air temperature.There were positive correlations between interception loss and rainfall, rainfall duration, and temperature.There were negative correlations between canopy interception loss and the interaction terms of rainfall with rainfall duration, air temperature.Non-significant correlations were found between throughfall, stemflow, and interception loss with antecedent dry time, wind direction, wind speed, photosynthetic available radiation, and net radiation, respectively.
Abstract: In order to accurately evaluate the water use efficiency in irrigation districts, several new indices were proposed to measure the efficiency and benefit of water use in this study.The water balance components are simulated using integrated surface and groundwater models in the Liuyuankou Irrigation District (LID).Thus, the new indices take into account the influence of return flows.The Statewide Agricultural Production (SWAP) model and a liner model are used to simulate the crop yields in the LID.On this basis, the indices measuring water use efficiency and benefit can be calculated and analyzed for different patterns of water-use. The influence of various water saving measures on the efficiency and benefit of water use is discussed.Results show that although, over different regions of LID, the results of well-canal combined irrigation mode and water-saving irrigation mode can be different in terms of water use efficiency.The use of both modes can improve the overall efficiency and benefit of water use in the LID.The study provides a theoretical method and theoretical basis for the water use assessment in irrigation districts.
Abstract: The water quality in the Xueyan town of the Taihu Lake basin was continuously monitored for 12 consecutive months from March 2009 to February 2010 during which two typical rainfall events were encountered.Accordingly, a study on the regularity and characteristic form of nitrogen losses was conducted in the context of different river systems, months, regions, flooding and land-use types.In addition, three studying sites (Shangjian village, Longquan River, Xueyan town) with different spatial scales were selected for analyzing these pollution characteristics during the two rainfall events.The result shows that nitrogen in Xueyan town water is even worse than Category V, and the nitrogen’s most common form is found in the liquid state of nitrate nitrogen.Compared to flooding seasons, the level of nitrogen pollution will be higher over non-flooding seasons.The pollutant load is highly variable and unstable.More specifically, the nitrate nitrogen concentration the townships are lower than that in non-townships.However, the opposite is true for the ammonia nitrogen concentration.Most nitrogen losses are found in ponds, and woodlands (arbor more) had the lowest nitrogen loss.In tea gardens, the nitrate nitrogen has the highest percentage of dissolved nitrogen; while the ammonia nitrogen is the predominant compound in dissolved nitrogen in orchard gardens.Before runoff being generated during a rainfall event, the nitrogen loss is stable.With the increase of runoff, the loss will increase.The increase rate is along different sections of a river.
Abstract: During the process of pollutants release due to sediment re-suspension, particles and pore water alternately affect the release flux to the overlying water. Conservative tracer (NaCl) and reactive tracer (Phosphorus) were respectively used as the contaminants to characterize the different ways of particles and pore water under hydrodynamic conditions in a laboratory flume. Studies have shown that reactive tracer responded more slowly to the bed shear stress than the conservative tracer did. Pollutants release process under constant flow can be divided into two significant stages: The suspended particles were in the desorption state during the first two hours, the ratio of water-soluble pollutants contribution between particles and pore water got a maximum values of 3:1. After two hours, the particles begun to adsorb contaminants instead, and the contribution rate of the particles was always negative while pore water’s contribution rate peak reached 60:1. The partition coefficient of pollutants first increased and then stays low, and the reactive pollutants mainly made an impact on water quality in the form of particular. Comparing derived formulas with the experimental dates, the theoretical result increased linearly while the increasing trend of experimental one is slow after the first rapid increment.
Abstract: One dimensional and two dimensional field experiments were conducted to investigate soil water flux in frozen soil, based on tracer concentration changes and water balance analysis. A capillary bundle model was developed to incorporate the Hangen-Poiseuille law into the flow analysis in frozen soil. The model demonstrated how the soil water flux changes as function of liquid soil water content and hydraulic conductivity. Results showed that the effect of water potential and temperature gradient caused liquid water to accumulate near the freezing front to form the maximum water flux. Water flux was influenced by the intermediate frozen soil layer blockage and groundwater movement during the thawing of soil from two directions: the surface downward and the bottom upward. The capillary bundle model well described water flow in the frozen soil under various temperature conditions and was a useful tool to characterize water movement in the water-ice and soil system.
Abstract: Estimation on annual greenhouse gas fluxes in reservoirs is crucial for the assessment of reservoir greenhouse gas effects. A 1a research was conducted in Pengxi River backwater area, Three Gorges Reservoir to estimate annual water-air CO2 and CH4 fluxes. Taken the 24h continuous monitoring data in Gaoyang Lake as reference, 2 methods, i.e. underwater topographical method and environmental controlling factor method, were carried out to estimate the annual fluxes based on monthly field data. The field sampling results showed that mean value of the CO2 fluxes among the sampling spot was (3.05±0.46) mmol/(m2· h), while that of CH4 was (0.050 1±0.009 6) mmol/(m2·h). The annual estimation of CO2 and CH4 fluxes in the Pengxi River backwater area based on underwater topographical method was 40 060.5 t and 540.9 t respectively. With the environmental controlling factor method, the annual estimation of CO2 and CH4 fluxes was 39 073.0 t and 467.2 t respectively. Taken the annual estimation result from environmental controlling factor method as reference, the weighted average CO2 fluxes during the study was 43.26 mmol/(m2·d), while that of CH4 was 1.42 mmol/(m2·d). Generally, both of the CO2 and CH4 weight average fluxes were shown to be in the mid-range in the global data sets, although that of CO2 was showed in slightly higher bound.
Abstract: This study tested the ability of four published pedotransfer functions (PTFs) (including ROSETTA, RAWLS, CAMPBELL and VAUCLIN) to predict unsaturated hydraulic conductivity for 56 sandy soil samples from the UNSODA database. Different PTFs for the estimation of saturated hydraulic conductivity were also evaluated in this study. Results showed that among the four PTFs, VAUCLIN produced the best performance, followed by ROSETTA and RAWLS, and CAMPBELL gave the worst performance when saturated hydraulic conductivity predicted by the identical PTFs as input. The performance of RAWLS, CAMPBELL and ROSETTA has been improved to different extent when measured saturated hydraulic conductivity as input. However, VAUCLIN did not produce the best performance when measured saturated hydraulic conductivity as input. The influence of saturated hydraulic conductivity on the predictive accuracy of unsaturated hydraulic conductivity was significant. Overall, CAMPBELL gave the best performance when the measured saturated hydraulic conductivity was used in the functions for estimation of unsaturated hydraulic conductivity.
Abstract: n this study, the relationships between soil saturated hydraulic conductivity and physical properties in different soil layers was examined with joint multifractal method, multi-scale prediction model of soil saturated hydraulic conductivity with above conclusions educed was established, and transformation relation of soil saturated hydraulic conductivity between different soil layers was constructed. The results showed that sorting of correlation degree between soil saturated hydraulic conductivity and physical properties in different soil layers was different; at single scale and multi-scale, sorting of correlation degree between soil saturated hydraulic conductivity and physical properties in 0-20 cm soil layer was same, and one in 20-40 cm soil layer was different; developed multi-scale prediction models of soil saturated hydraulic conductivity had high precision, and root mean square error of fitted soil saturated hydraulic conductivity in 0-20 cm and 20-40 cm soil layers was 0.035 0 and 0.029 0, respectively; precision of transformation relation of soil saturated hydraulic conductivity between 0-20 cm and 20-40 cm soil layers was high, and root mean square error of fitted soil saturated hydraulic conductivity was 0.037 5.
Abstract: Based on the cognition that numerical flow modeling is a regression process to prototype, from the correlation between model and prototype, a linear formulation that relates model’s and prototype’s Manning’s roughness coefficients(Manning’s n) is derived and a regression coefficient method for calibrating Manning’s n in shallow water equations is presented. Numerical tests show that the method does not only rely on the initial value of Manning’s n, but also has the attributes of good stability and fast convergence. Application to the complex flow simulation for the Modaomen channel indicates that the present method could improve the modeling precision, and has good adaptive, simple and practical abilities as well. It provides an effective way to determine Manning’s n in shallow water equations.
Abstract: Based on the sustainability and system theory, the connotation and features of Sustainable Water Resources System (SWRS) were discussed and the SWRS evolution forcing mechanism was put forwarded, that is, the SWRS is controlled by the interactions among dynamical, resistant, and coordinate mechanism. A quadratic nonlinear differential equation was used to describe the evolution process of SWRS quantitatively on basis of generalizing the influencing factors for SWRS evolution. The SWRS evolution follows a four-stage (initiation, growth, mature and steady) evolution cycle before it goes to the new evolution cycle. Further, taking Shanghai city as an example, the SWRS evolution equation was established by fitting method, and the evaluation results and the causes were given.
Abstract: Hyporheic layer of riparian zone is an active transition zone and ecotone between river and groundwater in riparian zone, which can be denoted respectively from hydrogeography, ecology and environment. Due to its unique structure properties in vertical, lateral and longitudinal directions, hyporheic layer of riparian zone was characterized to have some edge-effects and dynamic processes, including flow dynamics, ecological and chemical processes, which were driven by interactions among sediments, flow, communities, organic matters, solutes and environmental factors. As the three dynamic processes have affected each other and ecological and chemical processes have depended on flow dynamics driving and oxygen concentration, it has resulted that hyporheic layer in riparian zone could have stored floods and supplied suitable habitats and removed pollution. However, some of these functions were being weakened due to human and natural actions. In order to conserve the ecological balance and keep the sustainable development in riparian zone, it should be necessary to diagnose health status and verify weakening mechanism and practice ecological restoration. In future, according to the complex properties of riparian zones in our countries, it should be very important to investigate the responses of the hydrological, heat transportation, biochemical and ecological mechanisms to variation of hydrology, geomorphology, permeability, vegetation and riparian construction, and quantify the range of hyporheic layer and design the ecological restoration.
Abstract: Economic evaluation is important for flood-management policies and practices. The current paper reviews the progress in the theories on economic evaluation in flood management, the methods of flood damage evaluation, the cost-benefit assessment, as well as the shortcomings in these research activities. The traditional economic evaluation approaches that emphasizing on flood control could not meet the requirements in the new paradigm flood management. Future studies should pay more attentions on theoretical development for flood-management economic evaluation, the methods of assessing the benefits of nonstructural measures, the ecological and environmental impacts, and social justice in flood management.