Lower Pearl River Basin Research Articles

Reanalysis on Phylogeographic Pattern of Sharpbelly Hemiculter leucisculus (Cyprinidae: Cultrinae) in China: A Review and the Implications for Conservation

Hemiculter leucisclus, as a widely distributed freshwater fish in China, provides an interesting model to explore the impact of drainage evolution and geologic history in the Pleistocene on diversification patterns. We collected the mitochondrial cytochrome b (cytb) gene and the recombination activating gene 2 (RAG2) from 1,070 individuals from 59 sampling locations. Phylogenetic and population genetic approaches were used to describe the phylogeographic pattern and to test how the geological and climatic factors on diversification. The results suggested that there existed four sublineages of the H. leucisclus across six river systems, among which two sublineages, showing strongly indigenous characteristics, are constrained to particular geographical regions in China. The molecular data and ancestral states demonstrated that the H. leucisclus possibly originated from the Pearl River basin during the later Pliocene. The phylogeographic pattern in H. leucisclus appears to have been driven by palaeoenvironmental perturbations rather than anthropogenic translocations. The geographically constrained sublineages A in the middle and lower Pearl River basin and sublineage B in the upper Yangtze River basin deserves special protection.

Spatiotemporal variation of essential ecosystem services and their trade-off/synergy along with rapid urbanization in the Lower Pearl River Basin, China

The Lower Pearl River Basin (LPRB) of China has witnessed the rapidest urbanization in the world, along with which there has been significant spatiotemporal heterogeneity of essential ecosystem services and their trade-off/synergy within this rapid urbanization region. This study firstly explored the spatiotemporal heterogeneity of three essential ecosystem services (i.e., the carbon sequestration service, habitat quality and water yield) in the LPRB with the Integrated Valuation of Ecosystem Services and Trade-offs model based on time-series data during 1990–2015. This study then categorized the study area into different urbanization areas according to the urbanization level, and thereafter separately revealed the trade-off/synergy between these ecosystem services with correlation analysis on the sub-watershed scale. Results suggested the carbon sequestration service and habitat quality in the whole study area showed a slightly decreasing trend, while the water yield in the whole study area showed significant inter-annual fluctuation. Besides, there were obvious differences in the trade-off/synergy between three essential ecosystem services in different urbanization areas, indicating urbanization had important impacts on these ecosystem services and their trade-off/synergy. Specifically, there was always a significant synergy between the carbon sequestration service and habitat quality, which tended to decline and then keep stable as urbanization proceeds. While there was a trade-off between the carbon sequestration service and water yield, which tended to be firstly stronger and significant but then weaker and insignificant as urbanization proceeds. By contrast, there tended to be a decreasing but still significant trade-off between the habitat quality and water yield as urbanization proceeds. Moreover, there was an unusual trade-off/synergy between the water yield and the other two ecosystem services in 1990 and 2015, which was primarily due to the significant spatial variation of some relatively unstable factors (e.g., precipitation). It is necessary to take proper measures (e.g., sponge city construction, water transfer projects) to cope with the effects of these relatively unstable factors on the essential ecosystem services as urbanization proceeds. The results of this study can provide valuable supporting information for land use management to guarantee sustainable provision of essential ecosystem services in these rapid urbanization areas.

More frequent flooding? Changes in flood frequency in the Pearl River basin, China, since 1951 and over the past 1000 years

Abstract. Flood risks across the Pearl River basin, China, were evaluated using a peak flood flow dataset covering a period of 1951–2014 from 78 stations and historical flood records of the past 1000 years. The generalized extreme value (GEV) model and the kernel estimation method were used to evaluate frequencies and risks of hazardous flood events. Results indicated that (1) no abrupt changes or significant trends could be detected in peak flood flow series at most of the stations, and only 16 out of 78 stations exhibited significant peak flood flow changes with change points around 1990. Peak flood flow in the West River basin increased and significant increasing trends were identified during 1981–2010; decreasing peak flood flow was found in coastal regions and significant trends were observed during 1951–2014 and 1966–2014. (2) The largest three flood events were found to cluster in both space and time. Generally, basin-scale flood hazards can be expected in the West and North River basins. (3) The occurrence rate of floods increased in the middle Pearl River basin but decreased in the lower Pearl River basin. However, hazardous flood events were observed in the middle and lower Pearl River basin, and this is particularly true for the past 100 years. However, precipitation extremes were subject to moderate variations and human activities, such as building of levees, channelization of river systems, and rapid urbanization; these were the factors behind the amplification of floods in the middle and lower Pearl River basin, posing serious challenges for developing measures of mitigation of flood hazards in the lower Pearl River basin, particularly the Pearl River Delta (PRD) region.

DEVELOPMENT OF A FLOOD RISK ASSESSMENT MODEL FOR A BRAIDED RIVER SYSTEM

The aim of this study is to construct a modeling system that will assist flood risk management strategies in a coastal plain braided river system. The model configuration consists of a hydrodynamic model (ADCIRC) of the river basin that receives tidal forcing at the open boundary and river discharge forcing at upstream flux boundary. An unstructured mesh model resolving the Pearl River channels at higher resolution from the coastline to approximately 75km inland to upstream reaches of the river has been constructed. The modeling system produces water levels and currents throughout the Lower Pearl River Basin. Initial sensitivity analysis efforts on the channel model include consideration of low-flow, average-flow, and high-flow scenarios. Model results were found to be slightly sensitive to slope of river channels and bottom friction to control stability in predictions. The model results were shown to be highly sensitive to the bathymetry of the model that controls the discharge capacity of the narrow river channels and the channel model resulted in elevated currents and water levels under high flow conditions. A channel discharge capacity analysis was conducted and the results showed the need to construct a floodplain mesh around the channel model with more realistic bathymetry and topography so that the flooding scenarios could be modeled with wetting and drying capability of ADCIRC. An initial attempt to develop such a floodplain mesh has been made with preliminary results and more comprehensive validation of the developed floodplain modeling system will extend to reproducing events associated with the historical Hurricane Isaac that impacted the region in 2012. This modeling system will provide an important tool to decision makers that could be used in future flood risk management and mitigation efforts.

Response of vegetation to different time-scales drought across China: Spatiotemporal patterns, causes and implications

Based on Normalized Difference Vegetation Index (NDVI) and Standardized Precipitation Evapotranspiration Index (SPEI), we investigated vegetation response to different time-scales drought across different vegetation types and homogeneous clusters in China, by annual maximum Pearson correlation (Rmax) and the corresponding time-scales of drought. Results showed that: (1) 8 subregions with homogeneous climate-vegetation conditions were identified using Fuzzy C-Means algorithm; (2) SPEI and NDVI's annual Rmax were in significantly positive correlation in most regions of China, indicating that vegetation biomass were influenced mainly by the spatiotemporal characteristics of the water availability. The southeastern Yangtze River basin and the lower Pearl River basin are dominated by abundant precipitation, and vegetation is not sensitive to droughts in these regions. The northeastern Heilongjiang province, the Changbai Mountains and western Sichuan province are characterized by weak NDVI versus SPEI relations, indicating a relatively small effect of drought on vegetation; (3) The effects of annual average water balance, annual average annual precipitation, annual average effective accumulative temperature, and annual average daily sunshine hours on the NDVI versus SPEI correlation show that the annual average water balance is the key factor behind the change of vegetation vigor. It can therefore be concluded that the change of water availability is the key factor behind the change of vegetation activity and biomass. Regional precipitation or water balance was significantly related to the correlation between SPEI and NDVI. Vegetation in the regions with longer sunshine hours is more sensitive to droughts. In general, the sensitivity of grassland to droughts is the largest, followed by the sensitivity of shrubs and forests to droughts.

Nonstationarity-based evaluation of flood risk in the Pearl River basin: changing patterns, causes and implications

ABSTRACT Nonstationary GEV-CDN models considering time as a covariate are built for evaluating the flood risk and failure risk of the major flood-control infrastructure in the Pearl River basin, China. The results indicate: (1) increasing peak flood flow is observed in the mainstream of the West River and North River basins and decreasing peak flood flow is observed in the East River basin; in particular, increasing peak flood flow is detected in the mainstream of the lower Pearl River basin and also in the Pearl River Delta region, the most densely populated region of the Pearl River basin; (2) differences in return periods analysed under stationarity and nonstationarity assumptions are found mainly for floods with return periods longer than 50 years; and (3) the failure risks of flood-control infrastructure based on failure risk analysis are higher under the nonstationarity assumption than under the stationarity assumption. The flood-control infrastructure is at higher risk of flood and failure under the influence of climate change and human activities in the middle and lower parts of Pearl River basin. EDITOR D. Koutsoyiannis ASSOCIATE EDITOR G. Thirel

植被对不同时间尺度干旱事件的响应特征及成因分析

PDF HTML阅读 XML下载 导出引用 引用提醒 植被对不同时间尺度干旱事件的响应特征及成因分析 DOI: 10.5846/stxb201506111182 作者: 作者单位: 中山大学水资源与环境系,中山大学水资源与环境系,中山大学水资源与环境系,中山大学水资源与环境系,中山大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家杰出青年科学基金项目（51425903）；香港特别行政区研究资助局资助项目（CUHK441313）；中山大学滨海小流域自然地理综合过程观测与实验平台建设资助项目（2012年度）；中央高校基本科研业务费专项资金资助项目；广东省教育部产学研结合项目（2012B091100471） Vegetation responses to drought at different time scales in China Author: Affiliation: Department of Water Resources and Environment,Sun Yat-sen University,Department of Water Resources and Environment,Sun Yat-sen University,Department of Water Resources and Environment,Sun Yat-sen University,Department of Water Resources and Environment,Sun Yat-sen University, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:利用标准化降雨蒸散发指数（SPEI）与归一化植被指数（NDVI）系统研究了中国不同区域、不同土地利用类型的植被对不同时间尺度干旱事件的响应特征，并对成因做出探讨。研究表明：（1）全国大部分区域NDVI与SPEI呈显著正相关，表明中国大部分区域植被生物量变化受干旱时空特征的影响。而沿北纬30度附近的长江流域区域，尤其是长江流域东南部、珠江流域下游等降水相对丰沛区域；黑龙江东北部及长白山地区、四川西部等高寒区域，NDVI与SPEI表现出弱相关性，受干旱影响较小；（2）多年平均水平衡是影响植被对干旱响应的关键因素，土壤水分变化是植被活力与生物量变化的关键影响因子。多年平均日照时数较长的区域，植被变化受干旱影响较大。从对干旱影响敏感性程度来讲，越是水量丰沛的区域，植被受干旱的影响越小，其中，草地对干旱的影响最为敏感，其次为灌木与森林。 Abstract:NDVI and SPEI drought index are collected and analyzed to investigate vegetation responses to drought regimes at different time scales in different regions and vegetation types across China, and the causes of changes are discussed. The results show that: 1) SPEI and NDVI are significantly positively correlated in most regions of China, indicating that the changes in vegetation biomass are influenced mainly by spatiotemporal characteristics of available water. The southeastern Yangtze River basin and the lower Pearl River basin are characterized by abundant precipitation and vegetation that is not sensitive to drought. The northeastern Heilongjiang Province, the Changbai Mountains, and the western Sichuan Province are characterized by weak correlation between NDVI and SPEI, indicating small effect of drought on vegetation. (2) The effects of the average water balance, average annual rainfall, average annual effective accumulated temperature, and average daily sunshine hours on correlations between NDVI and SPEI show that the average water balance is the key factor behind the changes in vegetation vigor. Hence, it can be concluded that change in soil moisture is the key factor determining the changes in vegetation activity and biomass. Regional precipitation or water balance is related significantly to the correlation between SPEI and NDVI, whereas vegetation in the regions with longer sunshine hours is more sensitive to droughts. In general, grasslands are the most sensitive to droughts, followed shrubs and forest. 参考文献 相似文献 引证文献

Copula-based risk evaluation of droughts across the Pearl River basin, China

Daily precipitation data for the period of 1960–2005 from 42 precipitation gauging stations in the Pearl River basin were analyzed using the Mann–Kendall trend test and copula functions. The standardized precipitation index method was used to define drought episodes. Primary and secondary return periods were also analyzed to evaluate drought risks in the Pearl River basin as a whole. Results indicated that: (1) in general, the drought tendency was not significant at a 95 % confidence level. However, significant drought trends could be found in November, December, and January and significant wetting trends in June and July. The drought severity and drought durations were not significant at most of the precipitation stations across the Pearl River basin; (2) in terms of drought risk, higher drought risk could be observed in the lower Pearl River basin and lower drought risk in the upper Pearl River basin. Higher risk of droughts of longer durations was always corresponding to the higher risk of droughts with higher drought severity, which poses an increasing challenge for drought management and water resources management. When drought episodes with higher drought severity occurred in the Pearl River basin, the regions covered by higher risk of drought events were larger, which may challenge the water supply in the lower Pearl River basin. As for secondary return periods, results of this study indicated that secondary return periods might provide a more robust evaluation of drought risk. This study should be of merit for water resources management in the Pearl River basin, particularly the lower Pearl River basin, and can also act as a case study for determining regional response to drought changes as a result of global climate changes.

Production of Branched Tetraether Lipids in the Lower Pearl River and Estuary: Effects of Extraction Methods and Impact on bGDGT Proxies

Branched glycerol dibiphytanyl glycerol tetraethers (bGDGTs) are known as bacterial lipids that occur widely in terrestrial environments, particularly in anaerobic peat bogs and soil. We examined the abundance and distribution of bGDGTs in both core (C) and polar (P) lipid fractions from the water column and surface sediments in the lower Pearl River (PR) and its estuary using two extraction methods (sonication vs. Bligh and Dyer). A number of soil samples in the lower PR drainage basin were also collected and extracted for bGDGTs using the sonication method. The results showed aquatic production of bGDGTs as supported by substantial abundances of P-bGDGTs in the water column and sediment samples. The bGDGT-based proxies (BIT, CBT, and MBT) were not affected by the method of extraction when C-bGDGTs were analyzed; in such case, the pHCBT of the sediments reflected the soil pH of the lower PR drainage basin, and the temperature close to the annual mean air temperature (MAT) in the lower PR basin. On the other hand, the P-bGDGT-derived proxies were inconsistent between the two methods. The P-bGDGTs (particularly those extracted using the sonication method) may not be reliable indicators of annual MATs.

Copula-Based Analysis of Hydrological Extremes and Implications of Hydrological Behaviors in the Pearl River Basin, China

It is believed that the currently increasing temperature, also known as global warming, has altered the hydrological cycle and thus the hydrometeorological extremes become frequent. In this study, the authors analyze hydrological extremes defined by 7-day high flow and low flow of the Pearl River Basin by using a copula family. The results indicate that the concurrent occurrence of extreme high and low flow is of small probability. It implies that the probability is small that the lower Pearl River Basin is attacked by heavy droughts or floods because of the combined effects of high or low flow of the two major tributaries of the Pearl River, i.e., the West and North Rivers. Therefore, the authors can conclude that the joint probability of hydrological extremes of two tributaries of a river basin could be small, albeit the occurrence of hydrological extremes of an individual river is of large probability. Besides, the results of this study also reveal increasing 7-day low flow in winter, which should be b...

Multiscale variability of streamflow changes in the Pearl River basin, China

The Pearl River basin bears the heavy responsibility for the water supply for the neighboring cities such as Macau, Hong Kong and others. Therefore, effective water resource management is crucial for sustainable use of water resource. However, good knowledge of changing properties of streamflow changes is the first step into the effective water resource management. With this in mind, stability and variability of streamflow changes in the Pearl River basin is thoroughly analyzed based on monthly streamflow data covering last half century using Mann–Kendall trend test and scanning t- and F-test techniques. The results indicate: (1) significant increasing monthly streamflow is observed mainly in January–April, June and October–December. Monthly streamflow during May–September is in not significant changes. Besides, stations characterized by significant monthly streamflow changes are located in the middle and the lower Pearl River basin; (2) changing points of monthly streamflow series are detected mainly during mid-1960s, early 1970s, mid-1970s, early 1980s and early 1990s and these periods are roughly in good agreement with those of annual, winter and summer precipitation across the Pearl River basin, implying tremendous influences of precipitation changes on streamflow variations; (3) abrupt behaviors tend to be ambiguous from the upper to the lower Pearl River basin, which should be due to enhancing combined effects of abrupt changes of precipitation. The streamflow comes to be lower stability in recent decades. However, high stability of streamflow changes are observed at hydrological stations in the lower Pearl River basin. The results of this study will be of great scientific and practical merits in terms of effective water resource management in the Pearl River basin under the influences of climate changes and human activities.

Effects of temperature change on water discharge, and sediment and nutrient loading in the lower Pearl River basin based on SWAT modelling

The impact of climate change on hydrological processes and nutrient input is one of the major uncertainties in projecting future global warming. The Soil and Water Assessment Tool (SWAT) model is applied to simulate the effects of temperature on the hydrology and sediment and nutrient load in the lower Pearl River Basin, South China. Calibration and validation results for SWAT showed that the Yamen estuary is appropriate for simulating the impacts of temperature change on both hydrological processes and nutrient input. The possible temperature change scenarios were set at T–2, T–1.5, T–1, T–0.5, T+0.5, T+1, T+1.5, T+2, T+2.5, T+3°C compared to the current temperature, T°C. The results showed that the relative variation of discharge with temperature was slight. The sediment load at T+3°C is increased by 13.58% compared to that at T°C. Inorganic N and P inputs to the Yamen estuary showed an increasing trend with the temperature increase from T–2°C to T+3°C. Global warming can reduce the vegetation land cover by slowing plant growth, which will aggravate the water and soil loss. Temperature changes would have an effect on mineralization and nitrification by changing soil temperature and temperatures. The warming is projected to cause an increase of sediment and nutrient load into the estuary and accelerate eutrophication in the coastal area. Citation Li, Y., Chen, B.-M., Wang, Z.-G. & Peng, S.-L. (2011) Effects of temperature change on water discharge, and sediment and nutrient loading in the lower Pearl River basin based on SWAT modelling. Hydrol. Sci. J. 56(1), 68–83.

Changing properties of hydrological extremes in south China: natural variations or human influences?

AbstractExtreme events are drawing increasing concerns in recent decades due to their catastrophic nature. In this case, we thoroughly analysed the statistical behaviours of hydrological extremes in the south China by taking Guangdong province as a case study because of its unshakable position in the economic development in China. Our results further corroborated the fact that the hydrological changes are the integrated consequences of various external factors, basically the human activities and climate changes. Generally, decreasing annual maximum water (AMW) level was observed mainly in the seaward regions characterized by decreasing occurrence frequency of higher AMW level. Streamflow variations are influenced mainly by precipitation changes. Increasing annual maximum streamflow (AMS) can be attributed to the increasing precipitation intensity in recent years. However, in the East River basin, hydrological regulation function of the water reservoirs greatly reduced the AMS. In the lower East River, however, downcutting river channel and notable increases in the cross‐section area caused larger magnitude of decrease in AMW level when compared to AMS. The time when the relations between AMW level and streamflow start to change matches well the time when massive in‐channel sand dredging occurred, showing tremendous influences of human activities on hydrological processes in the lower Pearl River basin. This study will be of great scientific and practical merits in better understanding the statistical behaviours of hydrological extremes under the changing environment and also help to improve human mitigation to natural hazards in south China. Copyright © 2010 John Wiley & Sons, Ltd.