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Ran L.,National University of Singapore | Lu X.X.,National University of Singapore | Lu X.X.,Inner Mongolia University | Sun H.,CAS Institute of Geology and Geophysics | And 3 more authors.
Journal of Hydrology | Year: 2013

In this study, we examined the spatial and seasonal variability in the concentrations of dissolved and particulate organic carbon (DOC and POC) of the Yellow River. Weekly samples of water and suspended solids were collected along the main stem channel between July 2011 and July 2012 for the upstream Toudaoguai and Tongguan stations, and between August 2008 and July 2012 for the downstream Lijin station near the river mouth. The DOC export at the upstream two stations was primarily controlled by hydrological events such as melting of ice and snow with high DOC concentrations occurring in spring. In contrast, it was more affected by human activities, mainly reservoir regulation, at the lowermost Lijin station. Lower DOC concentration in the wet season indicates that most of the leachable DOC in surface soils may have largely been flushed away by spring floods. In addition, it is also likely due to dilution effect of the rapidly increased water discharge. As a result of low organic carbon content in the parent soils, the Yellow River sediments were characterized by low POC content (POC%). The averaged POC% at Toudaoguai, Tongguan, and Lijin was 0.48%, 0.47%, and 0.37%, respectively, which is significantly lower than the global mean of around 0.95%. The POC% decreased exponentially with total suspended solids (TSS) concentration. This is likely due to the dilution of riverine POC, because high TSS generally means a higher proportion of coarse sediments that have more mineral matter. During the study period, the total DOC and POC fluxes into the ocean were estimated at 0.06×1012g/yr and 0.41×1012g/yr, respectively. Combining our previous estimate of dissolved inorganic carbon (DIC) export shows that the Yellow River transports a carbon flux of 1.52×1012g/yr into the Bohai Sea, accounting for about 0.19% of the global total riverine carbon flux (DOC+POC+DIC). The extremely low DOC/POC ratio represents the lowest level among major world rivers, which is consistent with its intense soil erosion and highlights the effect of soil erosion on organic carbon export. © 2013 Elsevier B.V.

Hu Y.,Yellow River Conservancy Commission | Hu Y.,UNESCO-IHE Institute for Water Education | Maskey S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,Technical University of Delft
Climatic Change | Year: 2012

Spatial and temporal changes in daily temperature and rainfall indices are analyzed for the source region of Yellow River. Three periods are examined: 1960-1990, 1960-2000 and 1960-2006. Significant warming trends have been observed for the whole study region over all the three periods, particularly over the period 1960-2006. This warming is mainly attributed to a significant increase in the minimum temperature, and characterized by pronounced changes in the low temperature events composing a significant increase in the magnitude and a significant decrease in the frequency. In contrast to the temperature indices, no significant changes have been observed in the rainfall indices at the majority of stations. However, the rainfall shows noticeable increasing trends during winter and spring from a basin-wide point of view. Conversely, the frequency and contribution of moderately heavy rainfall events to total rainfall show a significant decreasing trend in summer. To conclude, this study shows that over the past 40-45 years the source region of the Yellow River has become warmer and experienced some seasonally varying changes in rainfall, which also supports an emerging global picture of warming and the prevailing positive trends in winter rainfall extremes over the mid-latitudinal land areas of the Northern Hemisphere. © 2011 Springer Science+Business Media B.V.

Xu W.,Tongji University | Ma W.,Tongji University | Yu F.,Yellow river conservancy commission
Journal of Convergence Information Technology | Year: 2010

An EPQ model for the co-operative supply chain under the conditions of permissible delay in payments is developed in this work, in order to compare the co-operative supply chain with non-cooperative supply chain; we also propose another EPQ model for the non-cooperative supply chain under the same conditions. In addition, we provide an efficient algorithm to obtain the optimal solution, and the results of numerical examples indicate that the cooperative supply chain will contribute to improving its EPQ and profit.

Xu X.-Z.,Dalian University of Technology | Li M.-J.,Heilongjiang Provincial Hydraulic Research Institute | Liu B.,Yellow River Conservancy Commission | Kuang S.-F.,China Institute of Water Resources and Hydropower Research | Xu S.-G.,Dalian University of Technology
Environmental Management | Year: 2012

A large number of soil and water conservation programs have been implemented on the Loess Plateau of China since the 1950s. To comprehensively assess the merits and demerits of the conservation practices is of great importance in further supervising the conservation strategy for the Loess Plateau. This study calculates the impact factors of conservation practices on soil, water, and nutrients during the period 1954-2004 in the Nanxiaohegou Catchment, a representative catchment in the Loess Mesa Ravine Region of the Loess Plateau, China. Brief conclusions could be drawn as follows: (1) Soil erosion and nutrient loss had been greatly mitigated through various conservation practices. About half of the total transported water and 94.8 % of the total transported soil and nutrients, had been locally retained in the selected catchment. The soil retained from small watersheds do not only form large scale fertile farmland but also safeguard the Yellow River against overflow. (2) Check dam was the most appropriate conservation practice on the Loess Plateau. In the selected catchment, more than 90 % of the retained soil and water were accomplished by the dam farmland, although the dam farmland occupied only 2.3 % of the total area of all conservation measures. Retention abilities of the characteristic conservation practices were in the following order: dam farmland > terrace farmland > forest land and grassland. (3) The conservation practices were more powerful in retaining sediment than in reducing runoff from the Loess Plateau, and the negative effects of the conservation practices on reducing water to the Yellow River were relatively slight. © 2012 Springer Science+Business Media, LLC.

Liu X.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Dai X.,Chinese Ministry of Water Resources | Zhong Y.,Beijing Hydrologic Center | Li J.,Yellow River Conservancy Commission | Wang P.,Jiangxi Normal University
Theoretical and Applied Climatology | Year: 2013

The Yiluo River is the largest tributary of the middle and lower Yellow River below the Sanmenxia Dam. Hydro-climatic variables have changed in the Yiluo River during the last half century. In this study, the trends in the annual precipitation and streamflow were analyzed in the Yiluo River during 1960-2006. The results indicated that both the annual precipitation and streamflow decreased significantly (P < 0.05) from 1960 to 2006. Pettitt's test shows that there was a change point for annual streamflow series around the year 1986 (P < 0.05), while there was no change point identified for the annual precipitation series from 1960 to 2006. Annual streamflow decreased more significantly than annual precipitation since 1986. The relationship between the annual precipitation and streamflow presented a non-stationary state since 1986. This non-stationary relationship was mainly influenced by human activities. The average annual amount of water diversion from the Yiluo River increased significantly since the mid-1980s, accounting for 31.3 % of the total streamflow decrease from 1986 to 2006. In addition, land use/cover change (LUCC) contributed to 27.1-29.8 % of the decrease in streamflow. Human activities, including water diversion and LUCC, together contributed to 58.4-61.1 % of the decrease in streamflow and led to the non-stationary relationship between the annual precipitation and streamflow from 1986 to 2006. This study detected the changes in the precipitation-streamflow relationship and investigated the possible causes in the Yiluo River, which will be helpful for the understanding of the changes in streamflow in the Yellow River Basin. © 2013 Springer-Verlag Wien.

Hu Y.,Yellow River Conservancy Commission | Hu Y.,UNESCO-IHE Institute for Water Education | Maskey S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,Technical University of Delft
Theoretical and Applied Climatology | Year: 2013

Three statistical downscaling methods are compared with regard to their ability to downscale summer (June-September) daily precipitation at a network of 14 stations over the Yellow River source region from the NCEP/NCAR reanalysis data with the aim of constructing high-resolution regional precipitation scenarios for impact studies. The methods used are the Statistical Downscaling Model (SDSM), the Generalized LInear Model for daily CLIMate (GLIMCLIM), and the non-homogeneous Hidden Markov Model (NHMM). The methods are compared in terms of several statistics including spatial dependence, wet- and dry spell length distributions and inter-annual variability. In comparison with other two models, NHMM shows better performance in reproducing the spatial correlation structure, inter-annual variability and magnitude of the observed precipitation. However, it shows difficulty in reproducing observed wet- and dry spell length distributions at some stations. SDSM and GLIMCLIM showed better performance in reproducing the temporal dependence than NHMM. These models are also applied to derive future scenarios for six precipitation indices for the period 2046-2065 using the predictors from two global climate models (GCMs; CGCM3 and ECHAM5) under the IPCC SRES A2, A1B and B1scenarios. There is a strong consensus among two GCMs, three downscaling methods and three emission scenarios in the precipitation change signal. Under the future climate scenarios considered, all parts of the study region would experience increases in rainfall totals and extremes that are statistically significant at most stations. The magnitude of the projected changes is more intense for the SDSM than for other two models, which indicates that climate projection based on results from only one downscaling method should be interpreted with caution. The increase in the magnitude of rainfall totals and extremes is also accompanied by an increase in their inter-annual variability. © 2012 Springer-Verlag.

Hu Y.,Yellow River Conservancy Commission | Hu Y.,UNESCO-IHE Institute for Water Education | Maskey S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,UNESCO-IHE Institute for Water Education | And 2 more authors.
Hydrological Processes | Year: 2011

Much of the discussion on hydrological trends and variability in the source region of the Yellow River centres on the mean values of the mainstream flows. Changes in hydrological extremes in the mainstream as well as in the tributary flows are largely unexplored. Although decreasing water availability has been noted, the nature of those changes is less explored. This article investigates trends and variability in the hydrological regimes (both mean values and extreme events) and their links with the local climate in the source region of the Yellow River over the last 50 years (1959-2008). This large catchment is relatively undisturbed by anthropogenic influences such as abstraction and impoundments, enabling the characterization of widely natural, climate-driven trends. A total of 27 hydrological variables were used as indicators for the analysis. Streamflow records from six major headwater catchments and climatic data from seven stations were studied. The trend results vary considerably from one river basin to another, and become more accentuated with longer time period. Overall, the source region of the Yellow River is characterized by an overall tendency towards decreasing water availability. Noteworthy are strong decreasing trends in the winter (dry season) monthly flows of January to March and September as well as in annual mean flow, annual 1-, 3-, 7-, 30- and 90-day maxima and minima flows for Maqu and Tangnag catchments over the period 1959-2008. The hydrological variables studied are closely related to precipitation in the wet season (June, July, August and September), indicating that the widespread decrease in wet season precipitation is expected to be associated with significant decrease in streamflow. To conclude, decreasing precipitation, particularly in the wet season, along with increasing temperature can be associated with pronounced decrease in water resources, posing a significant challenge to downstream water uses. © 2011 John Wiley & Sons, Ltd.

Qin D.,CAS Institute of Geology and Geophysics | Qian Y.,Yellow River Conservancy Commission | Han L.,International Atomic Energy Agency | Wang Z.,CAS Institute of Geology and Geophysics | And 2 more authors.
Journal of Hydrology | Year: 2011

Environmental tracers CFCs, 18O, 2H and tritium were used to determine the natural groundwater recharge and the impact of irrigation activity on the groundwater system in the semi-arid Zhangye Basin of China. Groundwaters in the irrigated areas have been identified as mixtures containing fractions recharged in different periods of time. The CFC and 3H data show that the oldest fraction in the groundwater was recharged before 1950, whereas the younger fractions were recharged in different periods of time since 1950. Stable isotope (18O, 2H), CFC and electrical conductivity data show that most of the samples can be regarded as binary mixtures with the river/irrigation water presents the younger fraction and the regional groundwater presents the older fraction. Binary mixing model is used to estimate the age and fraction of the younger component. Most of the younger fraction was recharged after 1980s, in response to the increasing irrigation activities. Compared to local precipitation surface water plays a major role in recharging the aquifer in the irrigated area. The irrigation activity had more impact on the aquifer under thin unsaturated zone (<10m), due to short travel times and high amounts of recharge, whereas it had less impact on the aquifer under thick unsaturated zone (tens of meters). CFCs are useful in identifying regions of different impact of irrigation return flow. The positive correlation between nitrate and CFC data show that contaminants are transported to the saturated zone by irrigation water. This study shows that in this semi-arid basin due to strong evaporation of infiltrating surface water and regional groundwater, δ18O and EC values, in contrast to CFCs, do not show simple relationship with NO3- concentration in groundwater. Combined with a proper mixing model, however, they can provide evidences that the CFCs found in groundwater were introduced by infiltrating irrigation return flow and, therefore, reveal that human activities can produce a much localized water circulation and influence groundwater vulnerability. © 2011 Elsevier B.V.

Hu Y.,Yellow River Conservancy Commission | Hu Y.,UNESCO-IHE Institute for Water Education | Maskey S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,UNESCO-IHE Institute for Water Education | Uhlenbrook S.,Technical University of Delft
Hydrology and Earth System Sciences | Year: 2013

Using the Statistical DownScaling Model (SDSM) and the outputs from two global climate models, we investigate possible changes in mean and extreme temperature indices and their elevation dependency over the Yellow River source region for the two future periods 2046-2065 and 2081-2100 under the IPCC SRES A2, A1B and B1 emission scenarios. Changes in interannual variability of mean and extreme temperature indices are also analyzed. The validation results show that SDSM performs better in reproducing the maximum temperature-related indices than the minimum temperature-related indices. The projections show that by the middle and end of the 21st century all parts of the study region may experience increases in both mean and extreme temperature in all seasons, along with an increase in the frequency of hot days and warm nights and with a decrease in frost days. By the end of the 21st century, interannual variability increases in all seasons for the frequency of hot days and warm nights and in spring for frost days while it decreases for frost days in summer. Autumn demonstrates pronounced elevation-dependent changes in which around six out of eight indices show significant increasing changes with elevation. © 2013 Author(s).

Li G.,Yellow River Conservancy Commission | Li G.,Northeast Normal University | Sheng L.,Northeast Normal University
Science China Technological Sciences | Year: 2011

Water-sediment regulation of the Yellow River is to regulate and control the flow and sediment transport relationship of the lower reaches through reservoirs on the main streams and tributaries to create balance between water and sediment so that sediment transport capacity of the downstream channels can be maximized, shrinking of channels be contained, and medium flood channel be restored and maintained. Many years' research by the Yellow River Conservancy Commission (YRCC) reveals the water and sediment transport relationship that will prevent sedimentation at the downstream river channels. Based on this relationship and coming sediment and water conditions in the Yellow River basin, the YRCC, with maximized use of reservoirs on the main streams and tributaries, has developed three models of water-sediment regulation: single Xiaolangdi Reservoir-dominated regulation, space scale water-sediment match, and mainstream reservoirs joint operation. Ten water-sediment regulations based on these three models have resulted in an average drop of 1.5 m in the main channel of the downstream 800 km river and an increase of carrying capacity from 1800 to 4000 m3/s. Besides, the wetland ecosystems of estuarine delta has also been improved and restored significantly. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

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