A framework for sustainable supply chain in emerging economies

Sustainable supply chains (SSC) are an essential topic in emerging economies for achieving sustainable development. Because of their rapid economic growth, emerging economies are experiencing both sides of this development: the well‐being enhancement and the environmental impact. However, decision makers and practitioners do not have robust models for managing supply networks that consider the sustainability complexities. This study aims to provide a better understanding of SSC in emerging economies and proposes a generic framework to improve the decision‐making process. Based on a review of the literature, a decision framework for sustainability is proposed. A green sustainable decision concept is also discussed in the SSC literature. This study has implications for scholars, decision makers, and practitioners interested in advancing the SSC field based on an extension of the framework.     

Company engagement with supply chains to protect biodiversity and rare,threatened, and endangered species

Future global megatrends project a population increase of 2 billion people between 2019 and 2050 and at least 1–2 billion people added to the global middle class between 2016 and 2030. In addition, 68% of the world's population is projected to be living in urban areas by 2050. With these projected large population increases and shifts, demand for food, water, and energy is projected to grow by approximately 35, 40, and 50%, respectively, between 2010 and 2030. In addition, between 1970 and 2014 there was an estimated 60% reduction in the number of wildlife in the world and an estimated net loss of 2.9 billion birds, or 29%, in North America between 1970 and 2018. Loss of species populations and number of species is interconnected with reduced health of biodiversity and ecosystems. Human activity has been the main catalyst for these substantial declines primarily through impacts on habitats. These losses are accelerating. Since a company's supply chain environmental impacts are often as great or greater than its own direct environmental impacts, it may be prudent for companies to engage with their supply chains to protect and enhance habitats and biodiversity and protect rare, threatened, and endangered species. As one example, companies may have opportunities and strategic reasons to include requirements in their supplier codes of conduct and supplier standards for suppliers to protect biodiversity and rare, threatened, and endangered species, as well as additional requirements to expand or enhance habitats and ecosystems to increase biodiversity. This article follows one pathway that companies could pursue further and with greater speed—to engage with their supply chains to strengthen supplier codes of conduct to protect biodiversity and rare, threatened, and endangered species. The importance of forests, private land, and landscape partnerships is discussed as means to protect much more of the planet's biodiversity and rare, threatened, and endangered species. Lastly, the article identifies examples of opportunities for companies to more formally incorporate biodiversity into their business, supply chain, and sustainability strategies.     

Assessing Retrospective National Water Model Streamflow with Respect to Droughts and Low Flows in the Colorado River Basin

Streamflow monitoring in the Colorado River Basin (CRB) is essential to ensure diverse needs are met, especially during periods of drought or low flow. Existing stream gage networks, however, provide a limited record of past and current streamflow. Modeled streamflow products with more complete spatial and temporal coverage (including the National Water Model [NWM]), have primarily focused on flooding, rather than sustained drought or low flow conditions. Objectives of this study are to (1) evaluate historical performance of the NWM streamflow estimates (particularly with respect to droughts and seasonal low flows) and (2) identify characteristics relevant to model inputs and suitability for future applications. Comparisons of retrospective flows from the NWM to observed flows from the United States Geological Survey stream gage network over 22 years in the CRB reveal a tendency for underestimating low flow frequency, locations with low flows, and the number of years with low flows. We found model performance to be more accurate for the Upper CRB and at sites with higher precipitation, snow percent, baseflow index, and elevations. Underestimation of low flows and variable model performance has important implications for future applications: inaccurate evaluations of historical low flows and droughts, and less reliable performance outside of specific watershed/stream conditions. This highlights characteristics on which to focus future model development efforts.     

Drivers of Interbasin Transfers in the United States: Insights from Sampling

Interbasin transfers (IBTs) are manmade transfers of water that cross basin boundaries. In an analysis of 2016 data, this work identified 2,161 reaches crossing United States (U.S.) Geological Survey hydrologic unit code 6 boundaries in the U.S. The objectives of this study were to characterize and classify IBTs, and examine the development drivers for a subset of 109 (~5%) of the IBT reaches through examination of samples from different climate regions of the U.S. The IBTs were classified as being near irrigated agricultural lands, near cities, or rural IBTs not near cities or irrigated land. IBTs near both cities and irrigated agricultural land were designated as city + irrigated agriculture. The 109 samples were selected, based on approximate proportional distribution to the total number of IBTs within each climate region, with representation of areas having a high density of IBTs. Analysis of the samples revealed that in the U.S., there have been four major drivers for basin transfers: irrigation for agriculture, municipal and industrial water supply, commercial shipping or navigation, and drainage or flood management. The most common has been drainage or flood management, though IBTs at least partially driven by agricultural needs are also prevalent. The majority of the sampled IBTs were constructed between 1880 and 1980, with peaks in development between 1900–1910 and 1960–1970. The samples also showed the drivers of IBT development evolved over time, reflecting changes in regional economies, populations, and needs.     

Assessment of Groundwater Depletion and Implications for Management in the Denver Basin Aquifer System

The Denver Basin Aquifer System (DBAS) is a critical groundwater resource along the Colorado Front Range. Groundwater depletion has been documented over the past few decades due to the increased water use among users, presenting long‐term sustainability challenges. A spatiotemporal geostatistical analysis is used to estimate potentiometric surfaces and evaluate groundwater storage changes between 1990 and 2016 in each of the four DBAS aquifers. Several key depletion patterns and spatial water‐level changes emerge in this work. Hydraulic head changes are the largest in the west‐central side of the DBAS and have decreased in some areas by up to 180 m since 1990, while areas to the northwest show increases in hydraulic head by over 30.5 m. The Denver and Arapahoe aquifers show the largest groundwater storage losses, with the highest rates occurring in the 2000s. The results highlight uncertainty in the volumetric predictions under various storage coefficient calculations and emphasize the importance of representative aquifer characterization. The observed groundwater storage depletions are due to a combination of factors, which include population growth increasing the demand for water, variable precipitation, and drought influencing recharge, and increased groundwater pumping. The methods applied in this study are transferable to other groundwater systems and provide a framework that can help assess groundwater depletion and inform management decisions at other locations.     

Federal Decentralization and Adaptive Management of Water Resources: Reservoir Reallocation by the U.S. Army Corps of Engineers

Reservoir operations must respond to changing conditions, such as climate, water demand, regulations, and sedimentation. The U.S. Army Corps of Engineers (Corps) can reallocate reservoir storage to respond to such changes. We assembled and analyzed a database of reservoir reallocations implemented and proposed by the Corps. While only a small portion of total reservoir storage nationwide has been reallocated, there are substantial differences in reallocation frequency and magnitude across the nation: some Corps Districts and Divisions use reallocation while others do not, relying more on discretion and small‐scale adaptation of operations. This difference illustrates how water resource agencies like the Corps decentralize management decisions to allow responding to disparate conditions. Decentralized decision‐making provides a responsive approach to water management, while centralized and hierarchical decision‐making is a slower, more deliberative approach. Decentralized decision‐making may lead to the accumulation of short‐term, local decisions over time to the point that the system is managed differently than anticipated. Reallocation, which is a form of planned adaptive management, can be accommodating of multiple competing demands and different stakeholders, yet expensive and less temporally responsive. The challenge for any large water resource management agency is to balance between local‐level, responsive discretion vs. centralized, planned decision‐making.     

Further studies on the influence of zeolite type A on metal transfer in the activated sludge process

Investigations were carried out to determine the effect of zeolite type A on metal removal by activated sludge using laboratory activated sludge simulations. They were operated at constant aerator sludge age and settler surface loading. Different concentrations of raw zeolite and zeolite extracted from washing powder (0, 15, 30, 60, 120 mgl^?1) were introduced into the simulations. The zeolite was added at two degrees of calcium exchanged for sodium, 25 and 75% of the maximum exchange capacity. Metals were added at concentrations typical of mixed domestic-industrial waste waters. The results show that there was no adverse effect on metal removal by the laboratory activated sludge simulations in the presence of zeolite type A.     

西北地区县域生态系统服务的供需匹配——以甘肃古浪县为例

作为人类福利的源泉,生态系统服务的供需特征及匹配状况反映了区域生态与环境资源的空间配置,分析其供需匹配关系是评价与优化生态系统服务管理、促进生态系统服务供需平衡的重要前提。以西北地区河西走廊东端的古浪县为例,利用气象观测、土地利用、统计年鉴等多源数据,基于InVEST模型、ArcGIS等方法,分析古浪县2017年的产水、碳固持、食物供给和土壤保持四项生态系统服务的供需及其匹配状况。结果表明：（1）古浪县产水、碳固持、食物供给和土壤保持服务供给与需求的总量均表现出供大于求的状态,其供求总量差值依次为：12.45×10⁸ m³、21.55×10⁷ t、3.8×10⁷ t、1.28×10⁷ t,且不同类型的生态系统服务供给与需求存在明显差异。（2）古浪县各项生态系统服务供需匹配类型可划分为高供给高需求、低供给高需求、低供给低需求、高供给低需求,不同区域与不同生态系统服务间的匹配模式存在明显的空间异质性。（3）古浪县生态系统服务供需匹配表现出南中北空间差异性,且呈现集中连片的态势,说明匹配类型相同的乡镇存在“相邻相似”的特征。基于对生态系统服务的供给、需求及匹配状况的分析,进一步提出了不同匹配类型下生态经济发展、城镇化建设、生态可持续化管理、国土空间规划等方面的优化对策。     

Effect of intermittent aeration mode on nitrogen concentration in the water column and sediment pore water of aquaculture ponds

Nitrogen in pond sediments is a major water quality concern and can impact the productivity of aquaculture. Dissolved oxygen is an important factor for improving water quality and boosting fish growth in aquaculture ponds, and plays an important role in the conversion of ammonium-nitrogen (NH₄⁺-N) to nitrite-nitrogen (NO₂^?-N) and eventually nitrate-nitrogen (NO₃^?-N). A central goal of the study was to identify the best aeration method and strategy for improving water quality in aquaculture ponds. We conducted an experiment with six tanks, each with a different aeration mode to simulate the behavior of aquaculture ponds. The results show that a 36 hr aeration interval (T_c = 36 hr: 36 hr) and no aeration resulted in high concentrations of NH₄⁺-N in the water column. Using a 12 hr interval time (T_c = 12 hr: 12 hr) resulted in higher NO₂^?-N and NO₃^?-N concentrations than any other aeration mode. Results from an 8 hr interval time (T_c = 8 hr: 8 hr) and 24 hr interval time (T_c = 24 hr: 24 hr) were comparable with those of continuous aeration, and had the benefit of being in use for only half of the time, consequently reducing energy consumption.     

Drought can offset potential water use efficiency of forest ecosystems from rising atmospheric CO2

Increasing atmospheric CO₂ is both leading to climate change and providing a potential fertilisation effect on plant growth. However, southern Australia has also experienced a significant decline in rainfall over the last 30 years, resulting in increased vegetative water stress. To better understand the dynamics and responses of Australian forest ecosystems to drought and elevated CO₂, the magnitude and trend in water use efficiency (WUE) of forests, and their response to drought and elevated CO₂ from 1982 to 2014 were analysed, using the best available model estimates constrained by observed fluxes from simulations with fixed and time-varying CO₂. The ratio of gross primary productivity (GPP) to evapotranspiration (ET) (WUEe) was used to identify the ecosystem scale WUE, while the ratio of GPP to transpiration (Tr) (WUEc) was used as a measure of canopy scale WUE. WUE increased significantly in northern Australia (p < 0.001) for woody savannas (WSA), whereas there was a slight decline in the WUE of evergreen broadleaf forests (EBF) in the southeast and southwest of Australia. The lag of WUEc to drought was consistent and relatively short and stable between biomes (≤3 months), but notably varied for WUEe, with a long time-lag (mean of 10 months). The dissimilar responses of WUEe and WUEc to climate change for different geographical areas result from the different proportion of Tr in ET. CO₂ fertilization and a wetter climate enhanced WUE in northern Australia, whereas drought offset the CO₂ fertilization effect in southern Australia.