Abstract: A framework is basically established for the evaluation of sedmient optmial allocation in them a instream of Yellow River.The framework is built on the systemic,hierarchical,representative,quantitative and com parable principles,and includes six evaluation parameters amiing at both technologic and economic subobjectives in the spatial optimization of sediment allocations.The procedure of calculating the six evaluation parameters is proposed.The synthetic evaluation function is presented.As the result,a method for comprehensive evaluation of sedmient optmia l allocations in the mainstream of Yellow River is determined.The method is used to evaluate 12 existing schemes of sediment optmial allocations in the Yellow River,and a preferable scheme is identified.The scheme suggests the optimal compositions of sediment allocations,which are 41.0% held in reservoirs,18.0% for land formation in estuaries,17.8% discharged into deep seas,10.4% consumed by irrigation,6.9% for siltation to beaches,3.8% for silting of mainstream,and 2.1% for silting flood plains.
Abstract: A expermient study was conducted to explore the effect of vegetation types on hillslope runoff, erosion, sediment yield,surface roughness and infiltration,as well as the interrelation among these elements. Results reveal that the effectiveness of vegetation regulating on hillslope runoff and sediment yield is in the folowing order:the plant root, the fully vegetated hillslope surface,the vegetation cover at the lower end of hillslope,and the vegetation cover at the upper end of hillslope. The forest-grassland regulates water storage and sediment yield through its rich root networks.Sedimentation retaining is directly achieved by the surface vegetation of grasslands.The cumulative sediment yield and the cumulative runoff are found to be exponentialy correlated.There are three stages of developing,active and stable in the development of hillslope runoff and sediment yield.The richer the vegetation coverage is,the less the surface roughness is.The result is useful for understanding of the runoff generation process at a catchment scale and provides reliable experimental in formation for the model development.
Abstract: The transverse water surface slope and secondary flow are main hydraulic features of bend flows,which are the result of the interaction bewteen the gravity and the centrifugal force in bend flows.The hydrodynamic characteristics of bend flows such as the water surface slope,the longitudinal velocity,the transverse circulation,the turbulence kinetic energy and the in tensity of secondary flow vary with the water depth in downstream.A series of flume experiments were conducted in a U-shape bend to study these hydrodynamic characteristics.Results show that the water surface slope,the longitudinal velocity,the turbulence kinetic energy and the intensity of secondary flow generally decrease with the increase of downstream water depths.The decline appears to be uneven in diferent sections of thebend.The results are favorable to further study on the effect of backwater to the structure of bend flows.
Abstract: The performance of groundwater modeling relies largely on the accurate estmiation of hydrogeological parameters,which are often influenced by the choice of optimization methods used.The particle swarm optimization(PSO)is a swarm in telligence technique for global optimization.However,the search efficiency of PSO decreases as the iteration process approaching to the end.It is thus desirable to search for the enhanced version of PSO.In this study,a hybrid global optimization algorithm that uses the Hooke-Jeeves(HJ)method for the bcal optimization and PSO for the global optimization is proposed to address the inverse problems in ground water modeling.Hydrogeological parameters can be determined using the new HJPSO algorithm.The result of a case study shows that HJPSO is characterized as an algorithm with accuracy,fast convergence and high robustness in the estmiation of hydrogeological parameters,and applicable to hydrogeologic parameters identification.
Abstract: The ensemble Kaml an filter(EnKF)is a sophisticated sequential data assimilation method.The EnKF has proven to be efficient handling of strong nonlinear dynamics and large state spaces.However,EnKF uses are latively small ensemble of forecasts to estmiate the forecast error covariance,which can introduce spurious correlations that lead to excessive decrease of the ensemble variance and possibly filter divergence.The spurious correlations can be handled by a localization method.In the method,the ensemble covariance matrix is multiplied with a specified correlation matrix through a Schur product(entry-wise multiplication),which can effectively truncate the long-range spurious correlations produced by the limited ensemble size.The revised EnKF is tested numerically for a two-dmiensional synthetic case.The result shows that localization can largely reduce the sampling errors due to small ensembles size with high eficiency,as well as can avoid filter divergence to a large extent.Applications of localization for the EnKF are also necessary to conduct localized corrections for the estimation of hydrogeological parameters with relatively small values of the correlation length.
Abstract: To counter the issues of groundwater overdraft and seawater intrusion,a smiulation-optimization model,coupled with recharge,pumpage and groundwater level,is established for the optimization groundwater management.The artificial fish-swarm algorithm is coupled with MODFLOW 2000,which is used to solve the management model.The management model is used in water saving irrigation region,Weihai city,Shandong province,to demonstrate the effectiveness and robustness of the management model. The result shows that the amount of groundwater pumpage reaches maxmium during October through December.From the point of maxmium,there will be a reduction in the pumping activity until next May.It is found that the permissible pumpage ranges from 3500 to 1120m3/month at well 1 in the coastal area,and 6540 to 2920m3/month in the non-coastal area.Comparing to the current plan for g roundwater operation,there will be increases in the total effective water supply of 1990 m3 and in the groundwater level of 0.29 m.The result is reasonable and feasible.The management model is applicable for optimizing groundwater management strategies in coastal areas.
Abstract: The subterranean karst stream services as an important water source to the groundwater supply system in the karst areas.There are approxinately 380 subterranean karst streams that supply groundwater to the areas of Chongqing municipalities.The hydrogeochemistry is studied for 61 subterranean karst streams in Chongqing.The result shows that the solutes are mainly originated from the dissolution of carbonate rocks through the water-rock interaction process.The groundwater chemistry is found to be of Ca-HCO3 type or Ca(Mg)-HCO3 type.However,the Na+Ca-HCO3、Na+Ca-SO4、Na+Ca-Cl or Ca-SO4+HCO3 type water have been detected in some of subterranean karst streams due to the influence of human activities.The impacts of agriculture activities and city sewages on hydrogeochemistry are more common than that of industrial and mining activities.The groundwater temperature gradually decreases with the increase of elevations.For the same geological setting,the presence of Ca2+、Mg2+、HCO3- exhibitssignificant regionality due to the discrepancy of karst processes in different areas.The same regionality is also found in the distribution of K+、Na+、SO42-、NO3-、Cl- because of human activities.The study concludes that the hydrogeochemical condition of Chongqing karst subterranean streams is deteriorating due to the industrial and agricultural activities as well as the discharge from the city sewage system.
Abstract: A crop green water occupancy index(CGWOI) is constructed on the crop green water consumption.Values of the CGWOI are calculated for all the 31 provinces of China from 1997 to 2007.The spatial autoco rrelation analysis is carried out to study the spatial and temporal variation of CGWOI.The result reveals that high values of CGWOI are in Chinas' Huang-Huai-Hai region,while regions with low CGWOI values are found in the west. The clustering phenomenon is clearly evident in the earlier spatial distributions of CGWOI.However,the weakening significance of the phenomenon has been dominated in the distributions.Combining results of both spatial and local autocorrelation analysis,the regularity of CGWOI spatial and temporal variations for the 31 provinces from 1997 to 2007 is also studied and discussed.
Abstract: As a commonly used method of calculating global solar radiation(Rs),the determination of the Angstromcoefficients(a and b)values play a vital role to the success of estmiating the reference crop evapo transpiration(ET0).At present, the values of 0.25 for a and 0.5 for b are used in the ungauged regions of China.Such valuesare recomm ended by the Food and Agriculture Organization of the United Nations(FAO).However,a comprehensiveassessment of the applicability of FAO recommended values in China must be done before they can be used with confidence to calculate global solar radiation.In this study,the effect of a and b on ET0 estmiation is investigated using the surface clmiatologic and solar radiation data measured at 104 meteorological stations distributed in China.Monthly values of a and b are calibrated with the observations,and their spatial and temporal variations are examined.The applicability of FAO recommended values in ET0 estmiation is tested over 7 geographic regions.A new regional method for determinating the Angstrom coefficient a and b values is proposed for China ungauged regions.The main conclusions of this study are:(1)ET0 is sensitive to the variability of a and b.The ET0 estmiate may contain a large error resulting from the use of FAO recommended values in Rs calculation in certa in regions.(2)The calibrated value of a at most stations is significantly smaller than 0.25 that is recommended by FAO,and the value of b is however much greater than 0.50.For example,in Xinjiang autonomous region and South China,the calibrated values of a and b exhibit are latively uniformed distribution,however this is not the case over other regions.(3)The FAO recommended values are useful in ET0 estimation with an acceptable accuracy in the areas of Xinjiang autonomous region,Northeast and Northwest China.However,the FAO values can result in severe overestmiation of ET0 in the regions of South and Southwest China.(4)A new regional method for estimating a and b is proposed,which can give a satisfactory result of ET0 estmiation when comparing to that of using the FAO recommended values.
Abstract: The multi-year spatial distribution and seasonal variations of c bud coverage and liquid water path of lower layer clouds over the Altay,Tianshan and Kunlun Mountain ranges in Xinjiang are analyzed by using the CERES(Clouds and the Earth's Radiant Energy System) SSF (Single Satellite Footprint) Aqua MODIS cloud data product from 2003 to 2007.The results show that the averaged multi-year cloud coverage of the three mountain ranges are in the range of 24.4%-27.5%,and the averaged multi-year cloud liquid water path are between 51g/m2and 56.3g/m2.Cloud coverage and liquid water path of lower layer clouds in the three mountainous regions exhibitlarge seasonal variations.Cloud coverage in spring and summer is larger than that in autumn and winter.Cloud coverage in spring is the most abundant,while the most abundant season for the cloud liquid water path is in winter for the three mountain regions.
Abstract: Using daily precipitation data for the period of 1951-2008 in Beijing,the study on the threshold values falling above the percentiles of the extreme events of precipitation,and the calculation of the threshold values with five methods,which are sorting,in terpolated,normal distribution transformation,square-root transformation,and cube root transformation,are researched in this paper.The results show that the evaluation of the threshold values using the method of square-root translation has the best effect in five methods.The mean of the threshold values on 30 year moving climatic period can be as the extreme events of daily precipitation in climate.
Abstract: The Water Evaluation and Planning(WEAP)model is applied to the itiaoxi watershed for an integrated water resources management study.The calibrated WEAP model is used to study the issues concerning the water quality and safety in the watershed for the period 2001-2020.The study includes the ecological function of river systems,quantification of future water demand,as well as sustainable water management practices.Problems associated with the current practices of water management are identified.The study finds that the water quality parameter total nitrogen(TN) is a restrictive factor that affects the safety of water supply in the riverhead protection zone.While,TN and total phosphorus(TP) are the factors that regulate the water function in the middle to lower reach of Xitiaoxi River.We propose that a good and efective integrated water management practice over a watershed should include wastewater treamtent plants,water saving devices,as well as implementation plans for conversion of farm land to forests to reduce the concentrations of TN and TP in the river system.Such a reduction in TN and TP concentrations could ensure the water quality and function in the entire river system meeting the III level standard throughout a year.
Abstract: Much attention has been paid to the cause of declining water resources in the Haihe River basin In this study,the Wutai Mountain region is chosen to assess the impact of decreasing orographic precipitation on water resources The orographic precipitation enhancement factor Ro is defined as the ratio between the hilly precipitation from Wutaishan station and the low land precipitation from 5 stations around the Wutai Mountain.A coupled water energy balance equation is used to evaluate the impact of decreasing orographic precipitation on water resources in the region.Results show that the value of the factor Ro is down by 0.53 in the past 50 years,or a reduction of 27%,indicating a significant decline in orographic precipitation and leading to a reduction of 190 million m3/y,about 26% of the mean annual runoff, received in the region,which can even account for 70% of the total reduction of water resources.In addition,the hilly precipitation is often underestimated due to the current precipitation gauge networks suffers from a shortage of precipitation gauges at the peak of mountains in many regions of China.As a result,the impact of orographic precipitation on water resources may not be properly evaluated.The reduction of water resources cou ld thus be under-evaluated when runoff is calculated from the gauge precipitation.
Abstract: To better assess water use status in irrigated agriculture and understand irrigation water use efficiency (WIUE) at different spatial scales,an improved distributed hydrological model,soil and water assessment tool (SWAT),is used to smiulate hydrological processes and the cropy ields in the irrigation region of the third main canal in Zhanghe irrigation district.The nine nesting scales is adopted to calculate the WIUE and to result in five IWUE indexes.The variation of five assessment indexes w ith the nine nesting scales is analyzed.Results show that one of theindexes,the irrigation water productivity,is greatly influenced by the spatial temporal distribution of precipitation as well as other weather conditions in the irrigation region.Its values increase with nesting scales.This scale character can be approximately represented by a power function that is smilar to the fractal principle.Another important index,the water drainage ratio,achieves the maximum value at the intermedium nesting scale.However,the scale character of the water drainage ratio is insignificant as this index is quasi-stationary across all nesting scales.Therefore,the power function can be used to scale up/down the irrigation water productivity.The greatest potential for water saving practice in this irrigation region is achievable at the intermedium nesting scale.
Abstract: Statistical hydrological forecasting models have been widely used for the medium and long term hydrological forecasting.One major concern for these models is how to choose an appropriate one with less imput and higher precision.The Charnes,Cooper and Rhodes(CCR)model for data envelopment analysis is used here for the multi-attributes evaluation of these forecasting models.In the CCR model, the inputs include indexes for forecasting factors and model parameters,the outputs include precision indexes,and the evaluation result is the relative efficiency of each model compared with other models.This method is used to evaluate 20 models of radial basis function networks for forecasting reference evapotranspiration.Results show that the CCR model is feasible for this kind of multi-attributes evaluation of forecasting models.Key factors for forecasting reference evapotranspiration are identified,which are maxmium and minmium temperature,wind speed and sunshine hours.Moreover,the forecasting precision and relative efficiency of a network could be miproved significantly if the date was added as an input of the network.
Abstract: Flushing of sedmients from reservoirs has always been one of the major issues in reservo ir operation on sedmient-laden rivers.Since reservoir recharge and sediment loading occur mainly during flooding seasons,the conflict of interests among the promotion of advantages (water supply) and the elmiination of disadvantages(sediment flushing) has becom eincreasingly conspicuous.Such a conflict could be resolved using the differential game theory.As the result,an optimization model is developed for a comprehensive solution of having mutual benefits among the two competing parameters.The solution can be used as the optimized plan for reservoir operations during flooding seasons.The model is tested using the observation from a reservoir on the Heihe River in the Shanxi province of China.The result shows that the model can adequately deal with the conflict of interests among the reservoir water supply and the reservoir sedmient flushing to achieve an optimized reservoir operation.
Abstract: We simulate the effect of strong waves on the sediment transport at the Xiaoqing River estuary areas using the 3D model ECOM SED(Estuarine Coasta lO cean Model with sedmient transport) with the wave parameters from the wave model SWAN(Simulating Waves Nearshore).The water depth,tidal current,suspended sedmient and historicalm eteorological data are used to estmiate the changes of the suspended sediment concen trations(SSC) and the bed scour and siltation(BSS) caused by strong wind and waves.We compare the smiulation with the in situ data and findthat the results are reliable.Results show that the sedmient transport change greatly under the influence of strong wind and waves in the near shore areas.The value of SSC is 10 times larger than that under the normal wind and wave condition.The change of BSS could be even as much as one hundred times.The result also show that the change of BSS resulting from strong wind and waves would have a great impact on the evolution of river estuary sandbars.
Abstract: The growth and decay processes of fast ice around Zhongshan Station in Antarctica were observed for two ice seasons of 2005 and 2006.Daily variations in the ice growth rate and its seasonal dependence are analyzed using in situ data.Although,cumulative freezing degree days during ice growth season of 2005 was larger than that of 2006,as the thicker snow cover,the ice growth rate and the maximum ice thickness of the former ice season were sm aller than those of the later one.The daily variation in the ice growth rate was evident during the periods before and after the polar night, but not for the polar night period.There was not any significant trend for both sea ice thickness and snow thickness with in the area 16 km north of Zhongshan Station vs.the distance to shore.The occurrences of ice ridge and iceberg,however,have crucial influences on local thickness distribution both for sea ice and snow.
Abstract: Rapid changes of river hydrodynamic conditions in cold regions can often lead to a mechanical breakup of river ice cover(known as" Wu Kai He" in Chinese)during winters or early springs.The formed ice ja s and dams on rivers result in a great danger to the public,causing the rise in water level and ice flooding.In this study,the mechanism of mechan ical breakup of river ice cover is investigated.The criterion for determining the mechanical breakup of river ice cover is proposed using a hydrothermal method.The criterion is validated using the field measurement from the Hequ reach of the Yellow River.The result shows that the ice breakup fo recast using the criterion is in good agreement with the observation.
Abstract: The agricultural drainage ditch,a vital component of agriculture hydrological facilities,plays an important role in agricultural production and national food security.As the problems of eutrophication and water quality deterioration are becoming more and more serious,a strong focus on the environmental impact and ecological function of agricultural drainage ditches has been getting attached.An agricultural drainage ditch is not only an most important element of agricultural landscape but also is able to regular the water balance of agricultural ecosystem and to improve the agricultural ecosystem.Nutrient in farm land can be rapidly lost from the farm land to the drainage ditch through the draining process Nutrient can also be removed from the agricultural ecosystem through the process of plant absorption and denitrification.A portion of nutrient losses to the ditch can be retained through the sedmientation and adsorption processes.Being the ecotone of the agroecosystem,rich plant diversities provide habitats and shelter places to anmial species,which increases the agro-biodiversity in the system Effects of different management practices,such as dredging,plant mowing and controlled drainage on environment and ecological function may vary in various aspects.In order to achieve a win-win result among utilizing of agricultural drainage ditches and ecoenvironmental protection,multi-discipline research on env ironm ental impact and ecological function of agricultural dra inage ditches shou ld be strengthened in the future.We should explore new techniques to build ecological drainage ditches,and introduce advanced management for ditch operation.
Abstract: The effect of urban nonpoint source pollution(NSP)on Chinas'water quality is being increasingly intensified.However,the regulation of polution has not been well established yet. Institutional deficits,insufficient information and lack of decision supports have been identified as three major restrictive factors in the practice of urban NSP management. Over the short term,laying a solid foundation for pollution in formation would be the first priority for the improvement of urban NSP management practice,which could also inspire institutional innovation.The long-term goal should be the establishment of a perfect institutional system to effectively addressing Chinas'pollution problems.Experiences on the institutional design and regulatory in formation developm ent from developed countries can provide China with valuable and intuitive references on the subject. Furthermore,advanced decision support techniques are critical to the success of the management practices.The latest in ternational development of urban NSP management showsChina directions for future research.