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Xu Y.,Hohai University | Zhang W.,Hohai University | Chen X.,Pearl River Hydraulic Research Institute | Zheng J.,Hohai University | And 2 more authors.
Journal of Coastal Research | Year: 2015

Salt intrusion in estuaries is an urgent environmental challenge across the world, because salinity influences water quality. The Modaomen Estuary is the main source of freshwater supply in the economically advanced Pearl River Delta, and it is experiencing a salt intrusion problem. Analytical models of salinity variation offer a simple and efficient approach to studying salt intrusion in estuaries. In this paper, two analytical models used worldwide to assess salinity variation in alluvial estuaries are applied to the Modaomen Estuary. The models are derived from salt convection-dispersion equations, with different assumptions for the dispersion coefficient. The performance of these two models was evaluated by comparing their results with field measurements; this revealed that both analytical models apply well to both the estimation of salinity distribution and the prediction of salt intrusion in the Modaomen Estuary. One model agrees more with the field measurements of salinity distribution along the estuary; the second better predicts salt intrusion length. ©Coastal Education and Research Foundation, Inc. 2015.


Liu Y.,South China Agricultural University | Zhou M.,South China Agricultural University | Chen Z.,Hydrology Bureau of Guangdong Province | Li S.,Administration Bureau of Hanjiang River Basin of Guangdong Province
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2013

Potential evapotranspiration (PET) as an estimate of crop water demand and a key input to hydrological modeling, not only affected by the changes in climate, but also affected by changes in vegetation covers. Sensitivity of PET to climate and vegetation is helpful in understanding the impact of climate changes and vegetation covers changes on water resources, and also is important to the optimal allocation of agricultural water resources. In this study, PET was calculated by Shuttleworth-Wallace (S-W) model. Threshold values of vegetation parameters in S-W model were drawn from the literature based on the International Geosphere-Biosphere Programme (IGBP) land cover classification. The spatial and temporal variation of vegetation leaf area index (LAI) was derived from the composite AVHRR NDVI using the SiB2 method. The long-term meteorological dataset at 752 meteorological stations in China was used to provide the required meteorological data. Using the meteorological data from meteorological stations and the monthly composite AVHRR NDVI data from NASA GIMMS during the period of 2000-2006, PET over Hanjiang River basin was estimated by S-W model. It showed that the PET was not only affected by climate, but also changed with vegetation types and the growth of vegetation. PET was very sensitive to vegetation types. The calculated PET of different vegetation in the similar climate condition is quite different. The annual mean PET of evergreen needle leaf forests, croplands and woods savannas was 1136.6, 965.1 and 563.2 mm/a, respectively. The maximum value was twice as the minimum value. The sensitivity of the PET to meteorological factors was analyzed. It showed that the sensitivity of the PET to climate was quite different for different vegetation covers. PET of evergreen needle leaf forests is the most sensitive to vapour pressure. Its sensitivity coefficient was much larger than that of air temperature and solar radiation. The sensitivity of wind speed can be ignored. PET of croplands was sensitive to air temperature, solar radiation and vapour pressure while it was not so sensitivity to wind speed. Among all the meteorological factors, the PET of croplands was the most sensitive to air temperature. PET of woods savannas was also the most sensitive to air temperature, and was also sensitive to vapour pressure, wind speed and solar radiation. Their sensitivity coefficients were very close to each other. The sensitivity of the PET to vegetation LAI was then analyzed. It showed that PET of all vegetation covers was sensitive to LAI, but the sensitivity coefficients were smaller than that of the meteorological factors (except for wind speed). The sensitivity of the PET to LAI was different for different vegetation covers. PET of woods savannas was the most sensitive to LAI, followed by evergreen needle leaf forests and croplands.


Zhang H.-J.,Jinan University | Chen X.-K.,Jinan University | Han B.-P.,Jinan University | Luo Y.,Hydrology Bureau of Guangdong Province | And 4 more authors.
Huanjing Kexue/Environmental Science | Year: 2012

Core sediments were collected from the riverine, transition and lacustrine zones of Hedi Reservoir in southern China to investigate the spatial distributions of nutrients and heavy metals and assess the potential ecological risk of heavy metals. The total nitrogen (TN) contents of the sediments at three sampling sites are between 2.314-2.427 mg·g-1, while total phosphorus (TP) contents range from 0.591 mg·g-1to 0.760 mg·g-1, TN contents of the surface sediments increase from the riverine zone to the lacustrine zone, but the TP content in the transition zone is higher than that in the other two sites (riverine zone and lacustrine zone). The mean contents of heavy metals are: 31.094, 46.85, 75.615, 385.739, 0.624 and 0.171 mg·kg-1 respectively, except Cr, the contents of heavy metals in sediment of lacustrine zone are higher than the sediment of transition zone. In all core sediments, the contents of nutrients and heavy metals decrease from the surface to the bottom of core sediments. Inorganic phosphorus (IP) is the dominant fraction of phosphorus in the sediment and the NaOH-P is the main forms of inorganic phosphorus. The potential ecological risk assessed by using of the highest environmental background values before industrialization as the reference indicates that each single heavy metal only causes slightly pollution, but two heavy metals (Cd and Hg) cause heavy pollution based on the soil environmental background values of Guangdong province. In spite of the slight difference between two kinds of risk assessment, all demonstrated that Cd and Hg resulted in more serious pollution than the other metals and these two metals contributed most to the RI values.


Zhang H.-j.,Jinan University | Gu J.-g.,Jinan University | Hu R.,Jinan University | Lin G.-e.,Jinan University | Wang Z.,Hydrology Bureau of Guangdong Province
Chinese Journal of Ecology | Year: 2012

To explore the characteristics of sediment heavy metals pollution and its history of four reservoirs in east coast of Guangdong Province, the main heavy metals Cr, Cd, Cu, Zn, Pb, and Hg in the sediments were detected, and the pollution status of surface sediments was evaluated with geo-accumulation index and Hǎkanson potential ecological risk index, respectively. The possible sources of the heavy metals were also discussed. In the surface sediments of the four reservoirs, the contents of the test heavy metals except Cd all exceeded the Class I values of the China National Standards of Soil Environmental Quality and the highest background values of heavy metals in the global sediments before industrialization, and had great variation between the reservoirs, indicating that the sediments of these reservoirs had been polluted in different degrees. Geo-accumulation index of the four reservoirs showed that the pollution degree of the heavy metals followed the order Pb>Zn>Cd>Cu>Cr>Hg, and Hǎkanson potential ecological risk index indicated that the potential ecological risk of the heavy metals followed the order Cd>Hg>Pb>Cu>Zn> Cr, of which, heavy metals Cd and Hg contributed most to the comprehensive ecological risk index (RI). The sediment heavy metals contents had a strong correlation with human activities, and the two assessments all showed that the pollution status of Gongping Reservoir and Chisha Reservoir with stronger human activities were worse than that of Hexi Reservoir and Tangxi Reservoir with less human activities.


Huang G.,South China University of Technology | Wu C.,South China University of Technology | Liu Z.,Chinese Ministry of Water Resources | Chen Z.,Hydrology Bureau of Guangdong Province | And 2 more authors.
Shuikexue Jinzhan/Advances in Water Science | Year: 2015

In this paper, the downscaling results of the multi-model dataset from the Coupled Model Intercomparison Project Phase 5 (CMIP5) were coupled with the Variable Infiltration Capacity (VIC) model to predict future floods of the Feilaixia reservoir in the Beijiang River basin under RCP2.6, RCP4.5, and RCP8.5 scenarios. Credibility of the projected changes in floods is described using an uncertainty expression approach, as recommended by the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC). The results indicate that annual maximum flood peak and maximum 7-day and 15-day flood volumes during 2020-2050 would be “about as likely as not” to show an upward trend under the RCP2.6 scenario and “more likely than not” to show an upward trend under the RCP4.5 and RCP8.5 scenarios. Compared with the 1970-2000 historical period, the flood peaks in the 100 a, 50 a, and 20 a return periods are projected to increase under all future scenarios. In contrast, the maximum 7-day and 15-day flood volumes in the 100 a, 50 a, and 20 a return periods would increase under the RCP4.5 scenario and decrease under the RCP2.6 and RCP8.5 scenarios. ©, 2015, China Water Power Press. All right reserved.


Wu C.,South China University of Technology | Huang G.,South China University of Technology | Yu H.,South China University of Technology | Chen Z.,Hydrology Bureau of Guangdong Province | Ma J.,Hydrology Bureau of Guangdong Province
International Journal of Climatology | Year: 2014

To evaluate the changes in extreme climatic events in the Feilaixia catchment in South China, the spatial and temporal distributions of extreme climate indices trends during 1969-2011 were investigated. With quality control and homogeneity assessment, daily maximum and minimum surface air temperature from 11 meteorological stations and daily precipitation from 24 rainfall stations were used. Eight indices of extreme temperature and six indices of extreme precipitation were chosen. Trends were calculated using Sen's slope estimator. Statistical significance of trends was checked with the Mann-Kendall method. High correlations were found between the mean annual temperature and temperature extremes, as well as between the annual total precipitation and precipitation extremes in most cases. The analyses of extreme temperature indices detected significant and stable trends in the majority of the stations. The strongly stable downward trends in cold extremes and the strongly stable upward trends in hot extremes were recorded in the whole region, except for in some small areas primarily located in the central part of the region. In contrast, significant and stable positive trends were sporadically recorded for precipitation extremes in the study area during 1969-2011, which predominantly occurred in the northern part of the region. Furthermore, the positive trends were much more frequent than the negative trends in most extreme precipitation indices. There were significant and stable trends recorded in most of the average temperature extremes, whereas insignificant and unstable trends were found for most of the average precipitation extremes. © 2013 Royal Meteorological Society.


Wu C.,South China University of Technology | Huang G.,South China University of Technology | Yu H.,South China University of Technology | Chen Z.,Hydrology Bureau of Guangdong Province | Ma J.,Hydrology Bureau of Guangdong Province
Journal of Hydrometeorology | Year: 2014

One of the potential impacts of global warming is likely to be experienced through changes in flood frequency and magnitude, which poses a potential threat to the downstream reservoir flood control system. In this paper, the downscaling results of the multimodel dataset from phases 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5, respectively) were coupled with the Variable Infiltration Capacity (VIC) model to evaluate the impact of climate change on the Feilaixia reservoir flood control in the Beijiang River basin for the first time. Four emissions scenarios [A1Band representative concentration pathway (RCP) scenarios RCP2.6, RCP4.5, and RCP8.5] were chosen. Results indicate that annual distribution and interannual variability of temperature and precipitation are well simulated by the downscaling results of the CMIP3 and CMIP5 multimodel dataset. The VIC model, which performs reasonably well in simulating runoff processes with high model efficiency and low relative error, is suitable for the study area. Overall, annual maximum 1-day precipitation in 2020-50 would increase under all the scenarios (relative to the baseline period 1970-2000).However, the spatial distribution patterns of changes in projected extreme precipitation are uneven under different scenarios.Extreme precipitation ismost closely associated with extreme floods in the study area. There is a gradual increase in extreme floods in 2020-50 under any of the different emission scenarios. The increases in 500-yr return period daily discharge of the Feilaixia reservoir have been found to be from4.35%to 9.18% in 2020-50. The reservoir would be likely to undergo more flooding in 2020-50. © 2014 American Meteorological Society.

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