Climate change uncertainty in environmental flows for the Mekong River

Abstract

A MIKE SHE model of the Mekong, calibrated and validated for 12 gauging stations, is used to simulate climate change scenarios associated with a 2°C increase in global mean temperature projected by seven general circulation models (GCMs). Impacts of each scenario on the river ecosystem and, hence, uncertainty associated with different GCMs are assessed through an environmental flow method based on the range of variability approach. Ecologically relevant hydrological indicators are evaluated for the baseline and each scenario. Baseline-to-scenario change is assessed against thresholds that define likely risk of ecological impact. They are aggregated into single scores for high and low flows. The results demonstrate considerable inter-GCM differences in risk of change. Uncertainty is larger for low flows, with some GCMs projecting high and medium risk at the majority of locations, and others suggesting widespread no or low risk. Inter-GCM differences occur along the main Mekong, as well as within major tributaries.

Editor Z.W. Kundzewicz

Citation Thompson, J.R., Laizé, C.L.R., Green, A.J., Acreman, M.C., and Kingston, D.G., 2014. Climate change uncertainty in environmental flows for the Mekong River. Hydrological Sciences Journal, 59 (3–4), 935–954.     

Biomarkers in environmental and human health risk assessment

Marine pollution is a major threat to human and environmental health. Given the complexity of function of marine and coastal ecosystems, it is unlikely that a balanced view of the nature and extent of risk will easily be achieved if human and environmental risk assessments continue to be conducted in isolation. Here, the integration of assessment protocols is advocated as a holistic means of improving risk management. Biomarkers can provide the common conceptual framework and measurable endpoints necessary for successful integration. Examples are given of the ways in which suites of biomarkers encompassing molecular change, cellular pathology and physiological impairment can be developed and adapted for human and ecological scenarios. By placing a greater emphasis on the health status of impacted biota, it is more likely that risk assessment will develop the efficiency, reliability and predictive power to adapt to the unforeseen environmental threats that are an inevitable consequence of human development and global change.     

Interactive spatiotemporal modelling of health systems: the SEKS–GUI framework

This paper describes the spatiotemporal epistematics knowledge synthesis and graphical user interface (SEKS–GUI) framework and its application in medical geography problems. Based on sound theoretical reasoning, the interactive software library of SEKS–GUI explores heterogeneous (spatially non-homogeneous and temporally non-stationary) health attribute distributions (disease incidence, mortality, human exposure, epidemic propagation etc.); expresses the health system’s dependence structure using (ordinary and generalized) spatiotemporal covariance models; synthesizes core knowledge bases, empirical evidence and multi-sourced system uncertainty; and generates a meaningful picture of the real-world system using space–time dependent probability functions and associated maps of health attributes. The implementation stages of the SEKS–GUI library are described in considerable detail using appropriate screens. The wide applicability of SEKS–GUI is demonstrated by reviewing a selection of real-world case studies. An erratum to this article can be found at     

Geographies of uncertainty in the health benefits of air quality improvements

Assessing the long-term benefits of marginal improvements in air quality from regulatory intervention is methodologically challenging. In this study, we explore how the relative risks (RRs) of mortality from air pollution exposure change over time and whether patterns in the RRs can be attributed to air quality improvements. We employed two-stage multilevel Cox models to describe the association between air pollution and mortality for 51 cities with data from the American Cancer Society (ACS) cohort (N = 264,299, deaths = 69,819). New pollution data were computed through models that predict yearly average fine particle (PM_2.5) concentrations throughout the follow-up (1982–2000). Average PM_2.5 concentrations from 1999 to 2000 and sulfate concentrations from 1980 were also examined. We estimated the RRs of mortality associated with air pollution separately for five time periods (1982–1986, 1987–1990, 1991–1994, 1995–1998, and 1999–2000). Mobility models were implemented with a sub-sample of 100,557 subjects to assist with interpreting the RR estimates. Sulfate RRs exhibit a large decline from the 1980s to the 1990s. In contrast, PM_2.5 RRs follow the opposite pattern, with larger RRs later in the 1990s. The reduction in sulfate RR may have resulted from air quality improvements that occurred through the 1980s and 1990s in response to the acid rain control program. PM_2.5 concentrations also declined in many places, but toxic mobile sources are now the largest contributors to PM in urban areas. This may account for the heightened RR of mortality associated with PM_2.5 in the 1990s. The paper concludes with a three alternative explanations for the temporal pattern of RRs, each emphasizing the uncertainty in ascribing health benefits to air quality improvements.     

Biomarkers and environmental risk assessment: guiding principles from the human health field

Although the potential use of biomarkers within environmental risk assessment (ERA) has long been recognised their routine use is less advanced compared with clinical human health risk assessment, where a number of familiar biomarkers (such as blood pressure and serum cholesterol) are in common usage. We have examined how biomarkers are incorporated into human health risk assessment and have identified several 'required elements'. These include identification of the (clinical) assessment endpoint at the outset, rational selection of the biomarker(s) (the measurement endpoint), biomarker 'validation' (e.g. QA/QC) and biomarker 'qualification' (evidence linking the measurement and assessment endpoints). We discuss these elements in detail and propose that their adoption will facilitate the routine use of biomarkers in environmental risk assessment. Furthermore, our analysis highlights the need for cooperation between those working with biomarkers within human and environmental risk assessment to exchange best practice between common disciplines for mutual advantage.     

Climate warming and the onset of salinization: Rapid changes in the limnology of two northern plains lakes

Water resources of the interior plains region of North America may be adversely affected by climate warming. The climate records of the Battleford region (west central Saskatchewan) indicate that mean annual temperatures have risen by 0.71 °C and mean annual minimum temperatures have risen by 1.03 °C from 1894 to 2007. Snowfall has also increased but total precipitation has not. Concomitant with periodic declines in precipitation, lake elevation has declined and salinity has increased in Jackfish and Murray lakes from 1938 to 2004. This long term increase in salinity is predicted to have caused an approximate 30% loss in diversity of macrobenthos. Phosphorus concentrations have also increased significantly, and Jackfish and Murray lakes would be classified as eutrophic by freshwater trophic indices. However, despite large increases in nutrients in both lakes, algal biomass has not increased and water transparency has not decreased. Although the total amount of planktonic biomass in Jackfish and Murray’s food web is similar to that of freshwater lakes, these lakes contain very low algal biomass (measured as chlorophyll a). In fact, such low algal biomass has not been previously observed in such dilute systems. The algal community in these shallow Prairie lakes appears to be very sensitive to slight changes in climate, and future climate driven increases in salinity of prairie lakes may result in large reductions in algal primary productivity.     

Climate change inferred from analysis of borehole temperatures: First results from Alberta Basin,Canada

High quality temperature measurements have been made to depths of 30 to 220 m at 42 sites in 62 observational hydrogeological wells in Alberta. The temperature profiles commonly show near-surface inversions with a minimum temperature at depths of 30 to 50 m. Thermal modelling suggests a surface temperature history with warming reaching 2°C over the past 30 to 60 years. Recent climate warming evident from the analysis of the air temperature data in the region seems to provide at least a partial explanation of the increased ground temperatures. A sudden increase of the surface ground temperature caused by land clearing may be the other explanation, although modelling of such a sudden increase can only explain the observed temperature-depth data if the onset of such warming is 20–30 years old, which is in disagreement with the history of land development in the studied area. The effect of near-surface inversions of the temperature profiles also has been observed in the forested areas. The above support the climate based effect. The superposition of the climatic effect and man-made activity effect upon the ground warming is a very complicated process calling for considerably more research.     

Global warming: a review of this mostly settled issue

Global warming and attendant climate change have been controversial for at least a decade. This is largely because of its societal implications since the science is largely straightforward. With the recent publication of the Fourth Assessment Report of the United Nations’ Intergovernmental Panel on Climate Change (Working Group 1) there has been renewed interest and controversy about how certain the scientific community is of its conclusions: that humans are influencing the climate and that global temperatures will continue to rise rapidly in this century. This review attempts to update what is known and in particular what advances have been made in the past 5 years or so. It does not attempt to be comprehensive. Rather it focuses on the most controversial issues, which are actually few in number. They are:

• Is the surface temperature record accurate or is it biased by heat from cities, etc.?
• Is that record significantly different from past warmings such as the Medieval Warming Period?
• Are human greenhouse gases changing the climate more than the sun?
• Can we model climate and predict its future, or is it just too complex and chaotic?
• Are there any other changes in climate other than warming, and can they be attributed to the warming?

Finally there is a very brief discussion of the societal policy response to the scientific message. Note that much of the introductory material in each section is essentially the same as that which appears in Keller 2003 (hereafter referred to as OR = original review) and its update (Keller 2007). Despite continued uncertainties, the review finds an affirmative answer to these questions. Of particular interest are advances that seem to explain why satellites do not see as much warming as surface instruments, how we are getting a good idea of recent paleo-climates, and why the twentieth century temperature record was so complex. It makes the point that in each area new information could come to light that would change our thinking on the quantitative magnitude and timing of anthropogenic warming, but it is unlikely to alter the basic conclusions.     

Model and parameter uncertainty in IDF relationships under climate change

Quantifying distributional behavior of extreme events is crucial in hydrologic designs. Intensity Duration Frequency (IDF) relationships are used extensively in engineering especially in urban hydrology, to obtain return level of extreme rainfall event for a specified return period and duration. Major sources of uncertainty in the IDF relationships are due to insufficient quantity and quality of data leading to parameter uncertainty due to the distribution fitted to the data and uncertainty as a result of using multiple GCMs. It is important to study these uncertainties and propagate them to future for accurate assessment of return levels for future. The objective of this study is to quantify the uncertainties arising from parameters of the distribution fitted to data and the multiple GCM models using Bayesian approach. Posterior distribution of parameters is obtained from Bayes rule and the parameters are transformed to obtain return levels for a specified return period. Markov Chain Monte Carlo (MCMC) method using Metropolis Hastings algorithm is used to obtain the posterior distribution of parameters. Twenty six CMIP5 GCMs along with four RCP scenarios are considered for studying the effects of climate change and to obtain projected IDF relationships for the case study of Bangalore city in India. GCM uncertainty due to the use of multiple GCMs is treated using Reliability Ensemble Averaging (REA) technique along with the parameter uncertainty. Scale invariance theory is employed for obtaining short duration return levels from daily data. It is observed that the uncertainty in short duration rainfall return levels is high when compared to the longer durations. Further it is observed that parameter uncertainty is large compared to the model uncertainty.     

Seacage aquaculture in a World Heritage Area: The environmental footprint of a Barramundi farm in tropical Australia

The fate of aquaculture wastes from a seacage farm within a pristine mangrove environment was studied. Seasonal and tidal differences were most important in determining water quality within receiving waters and obscured any nutrient enrichment effect by the farm. Farm wastes added significantly to the N budget status of the creek system, but overall water quality conformed to Queensland EPA Water Quality standards. Mangrove trees throughout the creek system contained ¹⁵N signatures traceable to aquaculture feeds, but the footprint of the farm itself was best indicated by the ratio of Zn:Li in sediments. The creek became hypoxic (<2 mg l⁻¹) during wet season low tides. Consequently, we recommended monitoring of water-column oxygen concentrations to warn of hypoxic conditions threatening to fish health, as well as Zn:Li ratios in sediment accumulation zones to determine the area of influence of the farm.     

Multiple interpretive errors? Indeed. Reply to: Climate effects of the 74 ka Toba super-eruption: Multiple interpretive errors in ‘A high-precision 40Ar/39Ar age for the Young Toba Tuff and dating of ultra-distal tephra’ by Michael Haslam

We would like to thank Michael Haslam (Haslam et al., 2013) for his interest in our recent contribution on the dating of the Young Toba Tuff/Tephra (YTT) (Mark et al., 2013). However, we point out errors made by Haslam, using this opportunity to clarify and expand on our discussion while also re-emphasising the important points from our study that have been overlooked.     

全球气候变化模拟结果数据的远程抽取及其可视化

本文针对气候模式在超大规模数值模拟中产生的Tb至Pb量级的四维体数据的可视化和分析诊断方法, 提出了基于Server-Client方式的远程数据抽取和并行可视化解决方案。 针对气候模拟数据中的海洋模式和大气模式数值模拟结果数据的抽取和可视化数值试验分析, 验证了解决方案的可行性和抽取算法的高效性、 可靠性和灵活性。 本文提出的远程数据抽取方法对于帮助气候模式领域中的专家快速抽取、 快速可视化和实现实时交互式模拟结果的诊断分析具有重要的应用价值。     

Ecological condition,biodiversity and major environmental challenges in a tropical river network in the Bago District in South-central Myanmar: First insights to the unknown

Freshwater ecosystems in the Indo-Burma biodiversity hotspot face immediate threats through habitat loss and species extinction. Systems to monitor ecological status and trends in biodiversity are therefore crucially needed. Myanmar is part of Indo-Burma but with no past experience of biomonitoring in freshwaters. In this study, we aimed to assess the ecological and biodiversity status of a lowland river network in south-central Myanmar by identifying and quantifying pressures using macroinvertebrates as bioindicators. Novel data on water quality (nutrients, sediments and metals), hydromorphology (Morphological Quality Index; MQI), habitat quality (Litter-Siltation Index; LSI), land use, and macroinvertebrates were collected from 25 river sites. The dominant pressures on rivers were urban land use, inputs of untreated sewage, in-stream and riparian garbage littering, run-off from agricultural fields and plantations, as well as physical habitat degradation. Water chemistry data indicated inputs of sediments and nutrients to degraded streams, but no obvious metal pollution. The LSI and MQI indices indicated high perturbation in agricultural and urban areas, respectively. Ecological status was assessed using a first version of a modified Average Score per Taxon index (ASPT), while biodiversity was assessed by family richness within the orders Ephemeroptera, Plecoptera, Trichoptera, Coleoptera and Odonata (EPTCO), which was tested against the pressure gradient by principal component regressions. ASPT had high diagnostic capabilities (R² = 0.68, p < 0.001) and showed that the index can be used to evaluate ecological water quality in this region. Biodiversity, expressed as family richness, also declined along the gradient (R² = 0.59, p = 0.041), giving support to the fact that current land-use practices in this area are unsustainable.     

Importance and necessity of integrated river basin management

It is obvious that water resources management has been an important issue in this century under the specified situation of climate change, regional development and population increase. Moreover, the modern life has become vulnerable to water environment effected with climate change. New water-related technologies may create the additional water consumption or drastic water saving. Freshwater withdrawals by human activities have increased dramatically over the years. Already, at the beginning of the 21st century, one-sixth of the world’s population was without access to improved water supply while two-fifths lacked access to improved sanitation. Problems of water resources have also become much discussed issues in international conferences and multi-national organizations.     

Mapping optimization based on sampling size in earth related and environmental phenomena

A critical sampling grid can be defined for an earth related natural variable distributed in space, according to established theoretical results and under certain mathematical conditions. Sampling above this critical limit does not substantially improve mapping results, while based on this limit the ideal process of reproducing the original phenomenon is theoretically defined. The aim of the present paper is, by using an innovative approach; to investigate the validity of commonly used interpolation algorithms, both stochastic and deterministic, below and above this critical sampling limit. When sampling is dense, application to a simulated spatial random field shows that the results are equally accurate with those derived with more sophisticated stochastic methods. On the other hand, when the sampling grid is sparse, deterministic methods produce less accurate results, therefore stochastic algorithms with minimum estimation error are a much better option. To further demonstrate these points, the interpolation algorithms were applied in three different sampling grid densities in a contaminated waste disposal site in Russia.     

格点大气环流模式GAMIL2参数不确定性的量化分析与优化

物理过程参数化方案的不确定性是目前气候系统模式不确定性的重要来源之一.随着模式内在复杂度攀升,模拟场景多样化,参数化方案中基于先验的和人工的物理参数选取方法已经逐步成为限制模式模拟能力的瓶颈之一.为此,本文设计并提出了初选与寻优相结合的两步法参数优化方案.初选阶段用全因子采样方法对不确定参数空间进行初始敏感性分析,估计最优解所在区域;寻优步采用单纯型下山法,基于初选阶段确定的参数组合快速寻优.将两步法应用于中国科学院大气物理研究所(英文缩写:IAP)大气科学和地球流体力学数值模拟国家重点实验室(英文缩写:LASG)格点大气模式第2版:GAMIL2,选取其深对流方案和云量方案中的3个重要参数开展寻优,优化以综合减小模式降水、风场、温度、湿度、位势高度以及辐射通量的误差为目标.这些变量用GAMIL2标准版本标准化后形成单一的目标. 结果显示,优化后的目标函数值比GAMIL2 标准版本改进了7.5%.机理分析表明,调优后的参数优化了大气中的水汽凝结作用,进而减少模式的湿度偏差,改进云量的模拟效果;同时水汽凝结作用的变化通过大气内部动力和热力相互作用及响应影响温度、位势高度和风场的模拟.     

Spatial variability in selenium and mercury interactions in a key recreational fish species: Implications for human health and environmental monitoring

Selenium’s (Se) protective effects against mercury (Hg) toxicity have been demonstrated; however, this is seldom considered in health assessments, where dietary exposure is still evaluated by Hg concentration alone. Se:Hg ratios and selenium health benefit values (Se HBVs) offer a more comprehensive seafood safety model. Here we describe total mercury (THg), methylmercury (MeHg) and Se concentrations in fish from a Hg-polluted estuary. Spatial variation in THg, MeHg and Se was evident, though all regions maintained Se:Hg ratio values >1. Se HBV varied between regions and in one region mean negative values (−5.17) were evident. This study provides the first evidence that quoting a single all-encompassing Se HBV is not appropriate when species demonstrate strong site fidelity. It highlights the need for research into Se–Hg relationships in environments with established Hg pollution and reinforces the assertion that Se concentration be considered in assessments of human health risk to Hg exposure.     

Climate,vegetation, and soil controls on hydraulic redistribution in shallow tree roots

Hydraulic redistribution defined as the translocation of soil moisture by plant root systems in response to water potential gradients is a phenomenon widely documented in different climate, vegetation, and soil conditions. Past research has largely focused on hydraulic redistribution in deep tree roots with access to groundwater and/or winter rainfall, while the case of relatively shallow (i.e., ≈1–2 m deep) tree roots has remained poorly investigated. In fact, it is not clear how hydraulic redistribution in shallow root zones is affected by climate, vegetation, and soil properties. In this study, we developed a model to investigate the climate, vegetation, and soil controls on the net direction and magnitude of hydraulic redistribution in shallow tree root systems at the growing season to yearly timescale. We used the model to evaluate the effect of hydraulic redistribution on the water stress of trees and grasses. We found that hydraulic lift increases with decreasing rainfall frequency, depth of the rooting zone, root density in the deep soil and tree leaf area index; at the same time for a given rainfall frequency, hydraulic lift increases with increasing average rainstorm depth and soil hydraulic conductivity. We propose that water drainage into deeper soil layers can lead to the emergence of vertical water potential gradients sufficient to explain the occurrence of hydraulic lift in shallow tree roots without invoking the presence of a shallow water table or winter precipitation. We also found that hydraulic descent reduces the water stress of trees and hydraulic lift reduces the water stress of grass with important implications on tree–grass interactions.     

气候变化对长江流域汉江和赣江径流的影响

近几年来,国家气候中心己经建立了中国主要四大流域气候对水资源影响评估的模式框架.本文拟进一步证明其中之一的两参数分布式月水量平衡水文模式对长江之上汉江和赣江两子流域径流的模拟能力,结果表明该水文模式对目前气候条件下径流模拟效果较好,运行稳定,可用于实时业务运行.在此基础上,利用ECHAM4和HadCM2两GCM(General Circulation Model)未来气候情景模拟结果及目前实测气候情况,对汉江和赣江两子流域的径流对未来气候变化的敏感性进行评估.经检验,两GCM对未来气候,特别是降水情景模拟存在一定差异,因此,造成径流对气候变化的响应不同,这充分反映了全球模式模拟结果不确定性在气候变化影响研究中的重要性.