The water–food–energy nexus: an introduction to nexus concepts and some conceptual and operational problems

This introduction sets the scene for the special issue compiled by Martin Keulertz, Eckart Woertz and Tony Allan.     

城市水系统关联模型研究

为了理清城市水系统中多因素间的复杂关系,对系统解决城市水问题提供帮助,基于水系统理论与城市水系统模拟相关研究,提出了城市水系统中水-经济社会-生态环境各因素之间相互作用和反馈的关联模型理论框架,建立了城市水系统演变过程中由针对经济发展的正反馈回路和针对可持续性的负反馈回路共同控制的新模式,构建了模拟城市水-经济社会-生态环境内在联系的城市水系统关联模型。以武汉市为例,应用建立的城市水系统关联模型,采用2001—2017年的历史统计数据,建立了武汉市城市水-经济社会-生态环境各要素之间互馈作用的模拟模型,预测了武汉市的城市发展轨迹,并与武汉市2030年的远期规划进行比较,验证了模型的有效性,表明城市水系统模型能够揭示城市水-经济社会-生态环境多要素的耦合驱动机制,体现了节水技术与绿色发展相关政策两大因子导向下的生态环境、经济社会协同发展的良好预期。     

我国现状能源与水纽带关系定量识别

以省级行政区为研究对象,以2017年为研究时段,分析我国社会水循环过程耗能及电力生产耗水。结果显示:2017年我国社会水循环过程耗电总量为10 828.1亿kW·h,占当年我国全社会用电总量的17.2%,终端用水是最大的耗能环节;2017年我国电力生产过程耗水量为65.7亿m~3,占当年全社会耗水总量的2%;火电是我国最耗水的电源,其耗水量占全国电力开发耗水总量的78%。基于计算结果,提出了实现能源-水协同安全的相关建议。     

Achieving water security in Nepal through unravelling the water-energy-agriculture nexus

ABSTRACT

This article investigates water security in Nepal from the perspective of the water-energy-agriculture (food) nexus, focusing on pathways to water security that originate in actions and policies related to other sectors. It identifies promoting development of Nepal’s hydropower potential to provide energy for pumping as way to improve water security in agriculture. Renewable groundwater reserves of 1.4 billion cubic meters (BCM), from an estimated available balance of 6.9 BCM, could be pumped to irrigate 613,000 ha of rainfed agricultural land in the Terai plains, with a potential direct economic gain of USD 1.1 billion annually and associated benefits including promotion of energy-based industry, food security and local employment. Governance also plays an important role in addressing water security. We conclude that a nexus-based approach is required for effective water management and governance.     

Climate Change and Trend Detection in Selected Rivers within the Asia-Pacific Region

Abstract

Global climate change is currently an issue of great concern. This phenomenon was studied using the runoff of large rivers, which can be considered a regional integrator of the local precipitation occurring in their basins. The long-term stationarity and the possibility of trends in streamflow records stored in the databank of the Global Runoff Data Center (GRDC) at the Federal Institute of Hydrology in Koblenz (Germany) were studied. Runoff records originating from 78 rivers with long monthly runoff series that are geographically distributed throughout the whole Asia-Pacific region were selected for study. For each of the selected rivers, three time series were constructed and analyzed: the mean yearly, and the maximum and minimum monthly discharges. These series were submitted to a two-tier analysis. First, a segmentation procedure developed by Hubert was applied to assess their stationarity. Then the segmented series were submitted to a specialized trend detection software. The results show that about two-thirds of the series have remained stationary and that the monthly minimum runoff exhibited more changing levels (37/78) than the mean (26/78) and maximum (18/78) runoff. Most of the detected changes occurred during the 1960s and 1970s, a period of rapid demographic expansion and urbanization in Asia, when irrigation and other water uses were developed, especially in tropical areas. During the same period and within the area studied, a number of large dams and reservoirs were completed. Since these anthropic interventions could be at the origin of the changes in runoff, there is no regionally consistent evidence supporting global climate change.     

黑龙江省水-能源-粮食系统动力学模拟

基于系统动力学理论,建立黑龙江省水-能源-粮食纽带关系仿真模型,对2010—2017年黑龙江省水资源的供需情况和能源、粮食的生产与消费进行模拟。通过设置和对比4种不同的发展方案,探究黑龙江省水-能源-粮食合理的配置方案。结果表明:黑龙江省的水资源安全形势较为严峻,在4种发展方案中,采取严格规划方案的正面效果最显著;强化发展方案下的能源消耗最明显,无论采取哪种发展方案,如果不对能源消费量加以控制,全省的能源安全可能无法保证;黑龙江省的粮食安全比较稳定,不易受外部条件的影响,保守节约方案下的粮食库存和粮食供需平衡比最大;仅采取一种发展方案可能无法实现水-能源-粮食系统的整体安全。     

中国水资源-能源-粮食纽带系统效率时空分异特征

采用SBM-DEA模型、网络DEA模型及双变量空间自相关方法对1997—2017年中国30个省级行政区的水资源-能源-粮食纽带系统(WEF系统)效率进行测度,并分析了其时空演化特征。结果表明:研究时段内,中国水资源、能源、粮食3个子系统的效率值呈现逐年上升趋势,水资源子系统、粮食子系统的效率值提升趋势明显,能源子系统效率值提升速度较为缓慢,空间分布上东部地区各子系统的效率值明显高于中部和西部地区;水资源子系统、能源子系统、粮食子系统效率值之间的空间相互作用存在一定差异,但协同作用的地区分布范围较为一致;中国WEF系统效率值呈波动上升趋势,而区域分布上,东部地区、东北地区、中部地区、西部地区的效率平均值呈依次下降的趋势,高效率区主要分布在东部沿海与黄河流域中下游地区,而西部地区则是低效率聚集区。     

中国水-能源纽带关系双向消耗核算研究

针对经济社会发展中水与能源的消耗问题,从水资源开发利用过程中的能耗与能源生产过程中的水耗两个角度进行双向的定量分析,并采用双向核算法估算了全国主要能源产业生产现状总用水量与水资源利用的总耗能量,厘清了水与能源之间的纽带关系。研究结果表明：水与能源之间存在着环环相扣的关系;6类能源中火力发电耗水量最大,水力发电次之,其后分别为原煤、原油、天然气,太阳能发电耗水量最小,2016年中国主要能源生产过程中耗水量约占全国用水总量的3.14%;水资源利用过程中地表水取水总能耗最大,非常规水源利用总能耗较小,2016年中国水资源利用过程中的能耗约占全国能源消耗总量的2.44%。     

Financial challenges of the nexus: pathways for investment in water,energy and agriculture in the Arab world

The Water–Energy–Food (WEF) nexus is a development challenge in the Arab world, particularly in the ‘core nexus countries’ with low to mid-incomes in which limited water endowments permit agricultural production, such as Egypt, Morocco, Tunisia, Lebanon, Algeria, Sudan and Jordan. The WEF nexus is often conceptualized in mere technocratic terms, yet politics matter in the implementation of projects that address it. Internalizing hydrological externalities or leaving them as they are and financing them as a public good requires states whose capacities have been reduced as a result of neoliberal reform. The article explores five different pathways of how Arab countries could finance green growth projects ranging from regional financial markets to concessionary loans by funds from oil rich Gulf countries.     

The nexus as a political commodity: agricultural development,water policy and elite rivalry in Egypt

Thinking of the interconnections between water, food, energy and climate is nothing new in the Nile Basin; it has long been anchored in political struggles. For 200 years, Egypt's political economy has been defined by water use patterns and food security strategies that debunk the technocratic myth that rapid growth, interaction with global markets and technological modernization eliminate poor governance practices and allocative inefficiencies. In contrast, the prism of the nexus as a political commodity illuminates one of modern Egypt's most consequential dialectics: the interaction between the very particular nexus at the heart of the country's political economy, forged through factional strife and sustained by outside discourses and interests, and the economic and ecological ravages of this elite politics. Egyptian history serves as a warning. Today's conversation needs to be deconstructed in terms of how different forms of interconnectivity between water, energy and food are produced and experienced by different social groups. It reminds us to take interconnections not as given, but rather as contested and contestable outcomes from which opportunities for adaptation and transformation do not naturally emerge, but need to be struggled for.     

山西省水-能源-粮食系统耦合协调时空变化特征研究

为探究山西省水-能源-粮食(W-E-F)系统耦合协调程度的时空变化特征,构建W-E-F系统评价指标体系,采用综合评价指数和耦合协调模型,测算全省及各地市2008-2017年W-E-F系统发展水平及其耦合协调程度,并分析其时空变动特征。结果表明:9年间全省W-E-F系统耦合协调度从0. 55上升到0. 83,总体达到良好协调水平。但各子系统发展特征不同,粮食子系统发展水平较高,表现稳定,水资源子系统发展滞后且稳定性较差。系统协调水平和各子系统的发展水平均存在显著且逐渐扩大的空间差异,2017年初级协调区和中级协调区占比分别为45%和55%。太原、忻州和晋中3市协调水平较高,协调水平较低的朔州和运城主要受能源和水资源子系统的制约;各子系统空间差异大小为能源>粮食>水资源,W-E-F各子系统发展水平最低的地区分别是运城、朔州、阳泉。大多数地区面临W-E-F系统内部发展日益失衡的问题,各子系统间存在突出的矛盾,主要表现为粮食和能源子系统与水资源子系统之间的压力和制约效应。最后提出促进山西省W-E-F系统协调发展的措施。     

基于水足迹与水-能源-粮食关联关系的提水灌溉系统种植结构优化

灌溉系统是农业生产与用水的关键载体,其水-能源-粮食关联关系的协调性对区域可持续发展有重要影响。相较于传统的灌溉水高效分配研究,水足迹理论明晰了农业生产水资源消耗总量及其利用类型。针对提水灌溉系统水资源、能源供需配置不紧密及其生态影响考虑不全面的问题,联合水足迹理论与水-能源-粮食关联关系,统筹社会、资源、生态和经济多维系统,构建了考虑水资源调配、农业生产用水及粮食生产转移全过程的提水灌溉区种植结构多目标优化评价模型。将该模型应用于涟水灌溉区,通过调整粮食作物(水稻、小麦、玉米和大豆)的种植结构,运用Topsis方法对比评价了现状和优化配置情况的相对贴近度。优化结果表明：在保障粮食安全的基本前提下,应增大玉米的播种面积,减少大豆的播种面积;相较于现状,优化后的年均粮食单方水经济净效益提升4.0%,作物碳足迹在农作物种植基线改变时呈现下降态势,且2018年优化后的碳足迹降低79.5 kg。优化方案的相对贴近度均大于现状,对促进提水灌溉系统资源高效利用和农业可持续性具有可靠的支撑作用。     

中国水—能源—粮食纽带系统安全水平与全要素生产率时空耦合协调关系分析

为研究中国资源系统与经济系统耦合协调发展状况,通过构建水-能源-粮食纽带系统安全评价指标体系,应用TOPSIS模型、DEA-Malmquist指数和耦合协调度模型,对中国30个省(自治区、直辖市)(不包括港澳台及西藏)水-能源-粮食纽带系统安全水平与全要素生产率进行了测算,从时间和空间的角度分析了二者耦合协调关系。结果表明：中国水-能源-粮食纽带系统安全水平呈“双极分布”的空间格局,整体安全水平逐年提升,粮食子系统安全水平最高,水资源子系统安全水平最低;2005—2019年中国全要素生产率呈波动上升态势,水-能源-粮食纽带系统与全要素生产率耦合协调时空格局差异显著,耦合协调度呈现上升趋势,空间格局由南至北呈现出“高—低—高”的空间分布特征,时间维度上耦合协调呈现向高水平耦合阶段演进的趋势。     

中国水资源-能源-粮食耦合系统安全评价及空间关联分析

采用Logistic曲线、耦合协调度模型和探索性空间数据分析等方法,对中国水资源-能源-粮食耦合系统进行安全评价及空间关联分析。结果表明:(1)随着经济的发展,中国多数省份水资源安全指数、能源安全指数和粮食安全指数呈上升的趋势;(2)中国水资源-能源-粮食耦合系统安全系数在2001—2015年多数省份呈上升趋势,而几个资源大省如河北、河南、山东、陕西等地耦合安全程度呈现波动或者下降的趋势;(3)从全局空间分异来看,中国各地区水资源-能源-粮食耦合系统安全性存在着空间集聚现象;从局部空间分异来看,空间正相关模式(低低和高高集聚)所占比例很大,低低集聚主要集中在西部和中部欠发达地区,而高高集聚主要分布在东部地区,在空间分布上比较稳定。     

基于用水总量的水- 能源- 粮食关系解析

随着社会经济的发展和人口的增加,我国能源和粮食需求持续增加,水资源短缺对其制约日益显现。为更深入地研究水资源、能源和粮食之间的关系,采用31个省、自治区、直辖市的实测统计并与定额推算相结合的方法,对能源开发利用和粮食生产种植的用水总量和过程进行分析。结果表明:2015年,煤炭开采洗选、火电行业、煤化工行业中的合成氨、炼焦行业的用水量分别占煤炭全生命周期用水量的2.9%～4.4%、90.4%～94.8%、1.5%～2.6%、0.8%～2.7%,煤炭全生命周期用水量合计达506.7亿～531.5亿m~3,占工业用水总量的38.0%～39.8%;农田灌溉用水量占农业用水总量的87.7%,实际亩均灌溉用水量394m~3,单位粮食产量的用水量为543.3m~3。研究成果可为水、能源、粮食之间的关系提供参考。     

Water security and the pursuit of food,energy, and earth systems resilience

ABSTRACT

This article addresses the emergence and interrelation of food, energy, and water security in terms of resource use and the ensuing societal and environmental outcomes. For decades, food security and energy security have been well-accepted, operational concepts. Water security is the latest entrant, yet the implications of water insecurity for food, energy and earth systems resilience have not been adequately considered. This article examines how and why this is so – particularly with growing water scarcity and insecurity that may compete with energy and food security – and emphasizes the critical need to link water-energy-food nexus approaches to earth systems resilience.     

Dynamics of wet‐season turbidity in relation to precipitation,discharge, and land cover in three urbanizing watersheds,Oregon

Frequent intense precipitation events can mobilize and carry sediment and pollutants into rivers, degrading water quality. However, how seasonal rainfall and land cover affect the complex relationship between discharge and turbidity in urban watersheds is still under investigation. Using hourly discharge, rainfall, and turbidity data collected from six stations in three adjacent watersheds between 2008 and 2017, we examined the temporal variability of the discharge–turbidity relationship along an urban–rural gradient. We quantified hysteresis between normalized discharge and turbidity by a hysteresis index and classified hysteresis loops during 377 storm events in early, mid, and late wet season. Hysteresis loop index and direction varied by site land cover type and season. Turbidity values peaked quicker in the watersheds with higher degrees of urban development than in a less urbanized watershed. The positive relation between discharge and turbidity was highest in two downstream stations in the mid wet season, whereas it was highest in two upstream stations in the early wet season. Correlation and regression analysis showed that maximum turbidity was best explained by discharge range, and the sensitivity of turbidity to discharge change was higher in the larger downstream watershed than in the small upstream watersheds. A flashiness index was negatively associated with the slope of turbidity versus discharge, suggesting that turbidity is difficult to predict solely on the basis of discharge in flashy urban streams. This paper contributes to a deeper understanding of the spatial and temporal variation of discharge–concentration relationship in urbanizing watersheds, which can help water managers increase the resiliency of water‐related ecosystem services to impacts of climate change.     

The rural–urban equity nexus of Metro Manila’s water system

ABSTRACT

This article examines equity concerns and inherent conflicts related to rural–urban water supply allocation and use, with focus on Metro Manila. Going beyond the much-discussed difficulty farmers experience from an allocation policy prioritizing urban water requirements, it shows that inequity in raw water allocation is linked to, and further exacerbated by, inequities in urban domestic water provision. Moreover, it highlights the need for broader equity reviews, using the concept of the rural–urban water equity nexus to draw attention to key equity considerations across space and scale that otherwise might remain invisible.     

Monitoring the channel process of a stream restoration project in an urbanizing watershed: a case study of Kelley Creek,Oregon, USA

Pacific Northwest (PNW) streams in the United States were impacted by the 20th century development, when removal of instream structure and channelization degraded an aquatic habitat. The lower Kelley Creek in southeast Portland, USA was channelized during the 1930's Works Progress Administration (WPA) projects. Stream restoration reintroduced pool‐riffle sequences and heterogeneous substrates to protect salmonids while mitigating impacts from flooding. We investigated whether the restored pool‐riffle morphology changed substantially following effective discharge events. We examined channel forms for four reaches representing three time periods—pre‐development (two reference reaches), development and restoration. We conducted thalweg profiles, cross‐sections and pebble counts along the reaches to examine how channel geometry, residual pool dimensions and particle size distribution changed following effective discharge events. The effective discharge flows altered the restoration reach more substantially than the reference reaches. The restoration reach decreased in median particle size, and its cross‐sectional geometry aggraded near its margins. However, the residual pool morphology remained in equilibrium. Richardson Creek's reference reach degraded at the substrate level, while Kelley Creek's reference reach remained in equilibrium. The restoration reach's aggradation may have resulted from sedimentation along the nearby Johnson Creek. In contrast, Richardson Creek's degradation occurred as upstream land use may have augmented flows. Stream channels with low gradient pool‐riffle morphologies are ideal for salmonid spawning and rearing and should be protected and restored within urban corridors. The findings of our study suggest that the connectivity of streams and the dynamic fluvial geomorphology of stream channels should be considered for stream restoration projects in humid temperate climates. Copyright © 2008 John Wiley & Sons, Ltd.     

城市化地区河网水系建设探析——以吴江市汾湖中心城区及产业园区为例

以吴江市汾湖中心城区及产业园区为例,针对土地利用开发过程中面临的水面积减小,河道淤积严重,水质恶化,洪涝灾害加剧,区内防洪压力加大等主要水系建设问题,通过实地调查和水系现状分析,探讨保护农村河网水系和改善农村水环境的主要措施:科学合理地进行水系调整规划,加强河道保护管理和基础设施建设,提高人们的环保意识,树立人水和谐的思想。