Multifractal analyses of daily rainfall time series in Pearl River basin of China

The multifractal properties of daily rainfall time series at the stations in Pearl River basin of China over periods of up to 45 years are examined using the universal multifractal approach based on the multiplicative cascade model and the multifractal detrended fluctuation analysis (MF-DFA). The results from these two kinds of multifractal analyses show that the daily rainfall time series in this basin have multifractal behavior in two different time scale ranges. It is found that the empirical multifractal moment function $K(q)$ of the daily rainfall time series can be fitted very well by the universal mulitifractal model (UMM). The estimated values of the conservation parameter $H$ from UMM for these daily rainfall data are close to zero indicating that they correspond to conserved fields. After removing the seasonal trend in the rainfall data, the estimated values of the exponent $h(2)$ from MF-DFA indicate that the daily rainfall time series in Pearl River basin exhibit no long-term correlations. It is also found that $K(2)$ and elevation series are negatively correlated. It shows a relationship between topography and rainfall variability.Comment: 16 pages, 7 figures, 1 table, accepted by Physica

Proposing a trend-based time-varying approach to assess climate- and human-induced impacts on streamflow

The conventional abrupt change-based assessments of climate- and human-induced impacts on streamflow require the existence of change point(s) and stationarity assumption. However, hydrological conditions may not change abruptly at a certain time, but rather evolve gradually over a period. We propose a trend-based time-varying approach that does not require these prerequisites to assess the climate- and human-induced impacts on hydrological conditions in the Pearl River Basin (PRB), China, which can be applied in other basins. The trend-based time-varying approach detects human activities exert a significant seasonal regulation on streamflow (i.e. 113% decreases in wet season and 93% increases in dry season) and 101% reductions in flood peaks the East River Basin, the sub-basin with the highest ratio of total reservoir storage capacity to river discharge in the PRB. Climate change contributes to 77% increases in flood peaks in the West River Basin, a large sub-basin with lower flood control levels

Correcting a major error in assessing organic carbon pollution in natural waters

Microbial degradation of dissolved organic carbon (DOC) in aquatic environments can cause oxygen depletion, water acidification, and CO2 emissions. These problems are caused by labile DOC (LDOC) and not refractory DOC (RDOC) that resists degradation and is thus a carbon sink. For nearly a century, chemical oxygen demand (COD) has been widely used for assessment of organic pollution in aquatic systems. Here, we show through a multicountry survey and experimental studies that COD is not an appropriate proxy of microbial degradability of organic matter because it oxidizes both LDOC and RDOC, and the latter contributes up to 90% of DOC in high-latitude forested areas. Hence, COD measurements do not provide appropriate scientific information on organic pollution in natural waters and can mislead environmental policies. We propose the replacement of the COD method with an optode-based biological oxygen demand method to accurately and efficiently assess organic pollution in natural aquatic environments

Evaluation of Future Water Use for Electricity Generation under Different Energy Development Scenarios in China

Water scarcity and uneven water demand in regional electricity generation pose substantial challenges to the sustainable development of water resources and electricity production in China. Based on the latest official policy of China’s electricity development, i.e., the 13th Five-Year Plan of electricity development, this study quantified annual water withdrawal and consumption for future electricity generation in China from 2015 to 2030. This study simulated a three-prong approach to impacting water use for electricity development, i.e., updating the cooling technology mix, increasing non-thermal power generation and relocating thermal power plants to the west. The results showed that solutions to relieve water stress caused by electricity production entail major trade-offs. Annual water withdrawal and consumption were projected to exceed 63.75 and 8.30 billion m3 by 2030, up approximately 14% and 21% of those in 2015, respectively, if China does not implement any new water and energy policies. Replacing once-through cooling systems with closed-loop cooling systems would decrease national water withdrawal remarkably but increase water consumption. The west-centered spatial distribution of thermoelectric power generation would reduce water use at the national level; however, it will largely increase water stress in northern and northwestern China. Thus, relieving the stress of growing electricity demand on water resources in China requires comprehensive measures and quantitative estimates

Climate regulation of Southeast Asian hydrology.

The Southeast Asian tropics extends from 23.5o North (Tropic of Cancer) to 11o South, and 90-140o East, and includes the countries of Brunei Darussalam, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, Timor-Leste and Vietnam. Southern China, notably the regions of Hong Kong, Guangdong, Guangxi, Hainan and Taiwan extend below the Tropic of Cancer at 106-122o East and are, therefore, climatologically part of the region. The region is also known as the ‘Maritime Continent’ because of its high proportion of sea, and the ‘Warm Pool’ because of its elevated sea-surface temperatures and consequent impact on evaporation and water vapour input to the upper troposphere (Newell and Gould-Stewart, 1981; Chen and Houze, 1997b). The high water vapour input to the upper troposphere makes SE Asia important for the global climate system (Neale and Slingo, 2003) and hence the global water cycle. The region exhibits climatic phenomena having important periodicities ranging from hours to decades (Nesbitt and Zipser, 2003; Franks and Kuczera, 2002). The strength and timing of these cycles and trends vary significantly over the latitudinal gradients from the equatorial zone to the Tropic of Cancer in the North and Lesser Sunda Islands (Nusa Tenggara) region to the South (Kripalani and Kulkarni, 1997). The spatial and temporal variability in the climatic cycles strongly affects the patterns in hydrology across the region. As a result, there are marked variations in the likelihood of flooding and droughts, the intensity of erosion and nutrient cycling, and the demand for irrigation water and water supplies. Further, the magnitudes of land-use change impacts on hydrology are also either - masked (Chappell and Tych, 2003) or regulated (Chappell et al., 2004b) by the region’s climate dynamics. This chapter aims to review influential and recent studies from SE Asia that show how hydrology is regulated by climate

Improving the effectiveness of planning EIA (PEIA) in China: Integrating planning and assessment during the preparation of Shenzhen's Master Urban Plan

The enactment and implementation of the 2003 EIA Law in China institutionalised the role of plan environmental impact assessment (PEIA). While the philosophy, methodology and mechanisms of PEIA have gradually permeated through the various levels of government with a positive effect on the process and outcome of urban planning, only a few cities in China have so far carried out PEIA as a Strategic Environmental Assessment (SEA)-type procedure. One such case is the southern city of Shenzhen. During the past three decades, Shenzhen has grown from a small town to a large and booming city as China has successfully and rapidly developed its economy by adopting the “reform and open door” policy. In response to the challenges arising from the generally divergent processes of rapid urbanisation, economic transformation and environment protection, Shenzhen has incrementally adopted the SEA concept in developing the city's Master Urban Plan. As such, this paper reviews the effectiveness of PEIA in three ways: •as a tool and process for achieving more sustainable and strategic planning; •to determine the level of integration of SEA within the planning system; and, •its effectiveness vis-à-vis implementation. The implementation of PEIA within Shenzhen's Master Urban Plan offers important insights into the emergence of innovative practices in undertaking PEIA as well as theoretical contributions to the field, especially in exploring the relationship between PEIA and SEA and highlighting the central role of local governing institutions in SEA development

STRATEGIC ENVIRONMENTAL ASSESSMENT IN CHINA: OPPORTUNITIES, ISSUES AND CHALLENGES

Based on literature reviews, case studies and other information available on the web, this paper examines the evolution and status of strategic environmental assessment in China by reviewing the progress that has been made; discussing the issues and problems encountered and exploring the best way forward. It is suggested that the Chinese EIA system has evolved over the years to cope with the rapidity and scale of development in China and the current emphasis on Plan EIA is probably the most appropriate form of SEA given the political reality and complicated institution setup. Given China's environmental and resource problems, the paper affirms the potential role of SEA in fostering a sustainable and harmonious society and the need to mainstream sustainability considerations in the formulation of national plans and strategies. To circumvent political resistance from line agencies, the paper suggests that SEA can be applied, in various names and forms, to national and provincial socio-economic plans.Strategic environmental assessment, stakeholder analysis, national socio-economic plan

Response of long-term water availability to more extreme climate in the Pearl River Basin, China

Under global warming, increasing temporal variability of climatic factors at various timescales (e.g. from inter-daily to inter-annual) has been reported in many places of the world over the past decades. The changes of temporal variability can be characterized by more extreme climate, such as more frequent and intensive heavy precipitation, less light rain days, and longer dry spells. These changes can subsequently bring about more frequent and intensive hydrologic extremes, including floods and droughts. This study shows that increase in inter-daily variability of precipitation and temperature not only triggers more intensive hydrologic extremes, but also causes considerable impacts on long-term water availability. Sixteen climate scenarios are designed to separate overall changes of precipitation and temperature into two aspects: (1) change in monthly mean and (2) change in inter-daily variability. Runoff of the Pearl River Basin (PRB) is simulated by the variable infiltration capacity (VIC) model under these scenarios. The results indicate that increase in inter-daily variability of the climate alone can lead to considerable increase in long-term water availability with reduced actual evapotranspiration (AET). The simulations also show that the inter-daily interaction between precipitation and temperature (i.e. lower temperature on a rain day) is important for long-term hydrologic simulations. The changing directions of simulated AET under scenarios with this interaction are opposite to those under scenarios without the interaction

Pluvial, fluvial and coastal flood risks and sustainable flood management in the Pearl River Delta under climate change

The Pearl River Delta (PRD) is the largest megalopolis region in the world, which is located at the estuary of the Pearl River Basin and dominated by sub-tropical and humid monsoon climate. This unique geographical setting makes the PRD highly exposed to pluvial, fluvial and coastal floods. Under climate change, the changes in precipitation regime intensify precipitation extremes, especially at the sub-daily scale, leading to higher risks of pluvial floods in the urban areas and fluvial floods in the riversides. Coastal floods also become more extreme due to the intensification of tropical cyclones and sea level rises. Future projections from CMIP5 Global Climate Models (GCMs) agree on further increases in the risk of these three types of floods, despite the uncertainties in the magnitude of changes. To counter the rising flood threat, PRD cities have adopted various measures to prevent and mitigate flood hazards. Hard measures, such as the three-pronged approach for pluvial flood prevention in Hong Kong and reservoir regulations for fluvial flood prevention for riverside cities, have been successfully implemented. To achieve sustainable flood management for future extreme floods, non-engineering measures should be further improved for playing a more important role in flood warning, prevention and mitigation