261-280 of 328 Results

Article

Smart Cities and Water Infrastructure  

Katherine Lieberknecht

Water infrastructure is the system of physical (both built and environmental), social (e.g., governance), and technological elements that move water into, throughout, and out of human communities. It includes, but is not limited to, water supply infrastructure (e.g., pipe systems, water treatment facilities), drainage and flood infrastructure (e.g., storm sewers, green infrastructure systems, levees), and wastewater treatment infrastructure (e.g., pipe systems, wastewater treatment plants, reclaimed water facilities). Smart city approaches to water infrastructure emphasize integration of information and communication technologies with urban water infrastructure and services, usually with the goal of increasing efficiency and human well-being. Smart water meters, smart water grids, and other water-related information and communication technologies have the potential to improve overall infrastructure efficiency, to reduce water use, to match new water supplies with appropriate water uses, to innovate wastewater treatment, and to protect residents from floods and other water-related climate events. However, without stronger attention to issues of equity, social systems, governance, ecology, and place, a smart city approach to water infrastructure may achieve efficiencies but fail to generate broader socioecological values or to contribute toward climate adaptation.

Article

Smart One Water: An Integrated Approach for the Next Generation of Sustainable and Resilient Water Systems  

Sunil K. Sinha, Meghna Babbar-Sebens, David Dzombak, Paolo Gardoni, Bevlee Watford, Glenda Scales, Neil Grigg, Edgar Westerhof, Kenneth Thompson, and Melissa Meeker

Quality of life for all people and communities is directly linked to the availability of clean and abundant water. Natural and built water systems are threatened by crumbling infrastructure, floods, drought, storms, wildfires, sea-level rise, population growth, cybersecurity breaches, and pollution, often in combination. Marginalized communities feel the worst impacts, and responses are hampered by fragmented and antiquated governance and management practices. A standing grand challenge for the water sector is transitioning society to a future where current silos are transformed into a significantly more efficient, effective, and equitable One Water system-of-systems paradigm—in other words, a future where communities are able to integrate the governance and management of natural and engineered water systems at all scales of decision-making in a river basin. Innovation in digital technologies that connect data, people, and organizations can be game changers in addressing this societal grand challenge. It is envisioned that advancing digital capabilities in the water sector will require a Smart One Water approach, one that builds upon new technologies and research advancements in multiple disciplines, including those in engineering, computer science, and social science. However, several fundamental knowledge gaps at the nexus of physical, social, and cyber sciences currently exist on how a nationwide Smart One Water approach can be created, operationalized, and maintained. Convergent research is needed to investigate these gaps and improve our current understanding of Smart One Water approaches, including the costs, risks, and benefits to diverse communities in the rural-to-urban continuum. At its core, implementing the Smart One Water approach requires a science-based, stakeholder-driven, and artificial intelligence (AI)–enabled cyberinfrastructure platform, one that can provide a robust framework to support networks of river-basin collaborations. We refer to this envisioned cyberinfrastructure foundation as the digital research and operational platform (DROP). DROP is envisioned to exploit advances in data analytics, machine learning, information, communication, and decision support technologies for the management of One Water systems via AI-enabled digital twins of river-basin systems. Deploying DROP at a large-basin scale requires an understanding of (a) physical water systems (natural and engineered) at the basin scale, which interact with each other in a dynamic environment affected by climate change and other societal trends and whose data, functions, and processes must be integrated to create digital twins of river basins; (b) the social aspects of One Water systems by understanding the values and perspectives of stakeholders, costs and benefits of water management practices and decisions, and the specific needs of disadvantaged populations in river basin communities; (c) approaches for developing and deploying the digital technologies, analytics, and AI required to efficiently operate and manage Smart One Water systems in small to large communities; (d) strategies for training and advancing the next-generation workforce who have expertise on cyber, physical, and social aspects of One Water systems; and (e) lessons learned from testing and evaluating DROP in diverse testbeds. The article describes a strategic plan for operationalizing Smart One Water management and governance in the United States. The plan is based on five foundational pillars: (a) river-basin scale governance, (b) workforce development, (c) innovation ecosystem, (d) diversity and inclusion, and (e) stakeholder engagement. Workshops were conducted for each foundational pillar among diverse stakeholders representing federal, state, and local governments; utilities; industry; nongovernmental organizations; academics; and the general public. The workshops confirmed the strong desire of water communities to embrace, integrate, and grow the Smart One Water approach. Recommendations were generated for using the foundational pillars to guide strategic plans to implement a national-scale Smart One Water program and facilitate its adoption by communities in the United States, with global applications to follow.

Article

Social and Environmental Implications of Plantation Agriculture in Malaysia and Indonesia  

Jean-François Bissonnette and Rodolphe De Koninck

Plantation farming emerged as a large-scale system of specialized agriculture in the tropics under European colonialism, in opposition to smallholding subsistence agriculture. Despite large-scale plantations in the tropics, smallholdings have consistently formed the backbone of rural economies, to the extent that they have become the main producers of some of the former plantation crops. In the early 21st century, oil palm has become the third most important cash crop in the world in terms of area cultivated, largely due to the expansion of this crop in Malaysia and Indonesia. Although in these countries, oil palm is primarily cultivated in large plantations, smallholders cultivate a large share of the territory devoted to this crop. This is related to the programs set up by governments of Malaysia and Indonesia during the second half of the 20th century, to provide smallholders with land plots in capital intensive large-scale oil palm schemes. Despite the relative success encountered by these programs in both countries, policymakers have continued to insist on the development of private centrally managed large-scale plantations. Yet, smallholding family farming has remained the most resilient economic activity in rural areas of the tropics. This system has proven adaptive to environmental change and, given proper access to markets and capital, particularly responsive to market signals. Today, many small-holdings are still characterized by the diversity of crops cultivated, low use of chemical inputs, reliance on family labor, and high levels of ecological knowledge. These are some of the main factors explaining why small family farms have proven more efficient than large plantations and, in the long term, more economically and ecologically resilient. Yet, large-scale land acquisitions for monocrop production remain a current issue, highlighting the paradox of the latest stage of agrarian capitalism and of its persistent built-in disregard for environmental deterioration.

Article

Social Equity, Land Use Planning, and Flood Mitigation  

Malini Roy and Philip Berke

Every flood event reveals hidden disparities within cities—disparities in capacities to anticipate, respond to, and recover from disasters. Studies examining drivers of disparity have found that highly socially vulnerable (e.g., poor, minority) neighborhoods sustain more damage, have access to fewer recovery resources, and experience slower recovery. Climate change and unregulated growth are likely to exacerbate these disparities. Scholars argue that disparities along the lines of race and income are partly due to inadequate planning. Planning for flood mitigation has lacked a deep understanding of values and has therefore overlooked needs and exacerbated physical vulnerability in socially vulnerable neighborhoods. Increasing local and international attention to the socioeconomic drivers of disaster impacts elicits the question: How can land use planning foster more equitable hazard mitigation practices that meet the needs identified by marginalized communities? Equitable hazard mitigation is advanced through three dimensions. First, contextual equity involves preparing an information base that asks who is vulnerable to flooding, who has (not) been engaged in planning decisions that affect vulnerability to flooding, and why. Recognizing contextual inequities in plans is the first step to making visible historic discrimination and addressing drivers of persisting political disenfranchisement. Second, procedural equity involves organizing a participation process that critically considers whom participation processes should target, how stakeholders should be inclusively engaged, and how multiple values should inform policy priorities. Dedicated planning-participation processes can repair past legacies of power information imbalances and co-produce planning goals. A process where vulnerable, marginalized citizens have as much information and as much say in policy decisions as others adds nuance to planners’ understanding of needs, and enables the incorporation of overlooked values into distribution of land use policies. Third, distributional equity involves designing planning policies so that flood mitigation services and infrastructure are directed to neighborhoods and households most in need. Moreover, distributional equity considerations need to be integrated across the local government plans (e.g., transportation plan, housing plan, and hazard mitigation plan) that affect growth in hazardous areas. Social equity outcomes further rely on the degree of knowledge transfer between the three dimensions. The effectiveness of distributional equity is critically dependent on contextual and procedural equity and affects how plan outcomes align with the needs and values of disadvantaged and vulnerable communities. Likewise, the scope of contextual equity is shaped by historical distributional and procedural equity or lack thereof. To advance equitable outcomes, more research is required on the implementation and effectiveness of different land use planning approaches. Future inquiries should examine social equity through a multihazard lens; empirically analyze the causal relationships among the contextual, procedural, and distributional equity; and explore the effectiveness of different planning tools and governance structures in fostering socially equitable hazard mitigation.

Article

Socio-Technical Transitions to Sustainability  

Frank W. Geels

Addressing persistent environmental problems such as climate change or biodiversity loss requires shifts to new kinds of energy, mobility, housing, and agro-food systems. These shifts are called socio-technical transitions because they involve not just changes in technology but also changes in consumer practices, policies, cultural meanings, infrastructures, and business models. Socio-technical transitions to sustainability are challenging for mainstream social sciences because they are multiactor, long-term, goal-oriented, disruptive, contested, and nonlinear processes. Sustainability transitions are being investigated by a new research community, which uses a socio-technical Multi-Level Perspective (MLP) as one of its orienting frameworks. Focusing on multidimensional struggles between “green” innovations and entrenched systems, the MLP suggests that transitions involve alignments of processes within and between three analytical levels: niche innovations, socio-technical regimes, and an exogenous socio-technical landscape. To understand more specific change mechanisms, the MLP mobilizes ideas from evolutionary economics, sociology of innovation, and institutional theory. Different phases, actors, and struggles are distinguished to understand the complexities of sustainability transitions, while still providing analytical traction and policy advice. The MLP draws attention to socio-technical systems as a new unit of analysis, which is more comprehensive than a micro-focus on individuals and more concrete than a macro-focus on a green economy. It also forms a new analytical framework that spans several stale dichotomies in environmental social science debates related to agency or structure and behavioral or technical change. The MLP accommodates stability and change and offers an integrative view on transitions, ranging from local projects to niche innovations to sector-level regimes and broader societal contexts. This new interdisciplinary research is attracting increasing attention from the European Environment Agency, International Panel on Climate Change (IPCC), and Organization for Economic Cooperation and Development (OECD).

Article

Soil Quality as Affected by Intensive Versus Conservative Agricultural Managements  

Luigi Badalucco

Soils, the earth’s skin, are at the intersection of the lithosphere, hydrosphere, atmosphere, and biosphere. The persistence of life on our planet depends on the maintenance of soils as they constitute the biological engines of earth. Human population has increased exponentially in recent decades, along with the demand for food, materials, and energy, which have caused a shift from low-yield and subsistence agriculture to a more productive, high-cost, and intensive agriculture. However, soils are very fragile ecosystems and require centuries for their development, thus within the human timescale they are not renewable resources. Modern and intensive agriculture implies serious concern about the conservation of soil as living organism, i.e., of its capacity to perform the vast number of biochemical processes needed to complete the biogeochemical cycles of plant nutrients, such as nitrogen and phosphorus, crucial for crop primary production. Most practices related to intensive agriculture determine a deterioration even in the short-middle term of their physical, chemical, and biological properties, which all together contribute to soil quality, along with an overexploitation of soils as living organisms. Recent trends are turning toward styles of agriculture management that are more sustainable or conservative for soil quality. Usually, use of soils for agricultural purposes deflect them at various degrees from the “natural” soil development processes (pedogenesis), and this shift may be assumed as a divergence from soil sustainability principles. For decades, the misuse of land due to intensive crop management has deteriorated soil health and quality. A huge plethora of microorganisms inhabits soils, thus acting as “the biological engine of the earth”; indeed, this microbiota serves the soil ecosystem, performing several fundamental functions. Therefore, management practices might be planned looking at the safeguard of soil microbial diversity and resilience. In addition, each unexpected alteration in numberless soil biochemical processes, being regulated by microbial communities, may represent an early and sensible signal of soil homeostasis weakening and, consequently, warn about soil conservation. Within the vast number of soil biochemical processes and connected features (bioindicators) virtually effective to measure the sustainable soil exploitation, those related to the mineralization or immobilization of the main nutrients (C and N), including enzyme activity (functioning) and composition (diversity) of microbial communities, exert a fundamental role because of their involvement in soil metabolism. Comparing the influence of many cropping factors (tillage, mulching and cover crops, rotations, mineral and organic fertilization) under both intensive and sustainable managements on soil microbial diversity and functioning, through both chemical and biological soil quality indicators, makes it possible to identify the most hazardous diversions from soil sustainability principles.

Article

Soil Resources, the Delivery of Ecosystem Services and Value  

David A. Robinson, Fiona Seaton, Katrina Sharps, Amy Thomas, Francis Parry Roberts, Martine van der Ploeg, Laurence Jones, Jannes Stolte, Maria Puig de la Bellacasa, Paula Harrison, and Bridget Emmett

Soils provide important functions, which according to the European Commission include: biomass production (e.g., agriculture and forestry); storing, filtering, and transforming nutrients, substances, and water; harboring biodiversity (habitats, species, and genes); forming the physical and cultural environment for humans and their activities; providing raw materials; acting as a carbon pool; and forming an archive of geological and archaeological heritage, all of which support human society and planetary life. The basis of these functions is the soil natural capital, the stocks of soil material. Soil functions feed into a range of ecosystem services which in turn contribute to the United Nations sustainable development goals (SDGs). This overarching framework hides a range of complex, often nonlinear, biophysical interactions with feedbacks and perhaps yet to be discovered tipping points. Moreover, interwoven with this biophysical complexity are the interactions with human society and the socioeconomic system which often drives our attitudes toward, and the management and exploitation of, our environment. Challenges abound, both social and environmental, in terms of how to feed an increasingly populous and material world, while maintaining some semblance of thriving ecosystems to pass on to future generations. How do we best steward the resources we have, keep them from degradation, and restore them where necessary as soils underpin life? How do we measure and quantify the soil resources we have, how are they changing in time and space, what can we predict about their future use and function? What is the value of soil resources, and how should we express it? This article explores how soil properties and processes underpin ecosystem services, how to measure and model them, and how to identify the wider benefits they provide to society. Furthermore, it considers value frameworks, including caring for our resources.

Article

Soil Salinization  

Pichu Rengasamy

Salt accumulation in soils, affecting agricultural productivity, environmental health, and the economy of the community, is a global phenomenon since the decline of ancient Mesopotamian civilization by salinity. The global distribution of salt-affected soils is estimated to be around 830 million hectares extending over all the continents, including Africa, Asia, Australasia, and the Americas. The concentration and composition of salts depend on several resources and processes of salt accumulation in soil layers. Major types of soil salinization include groundwater associated salinity, non–groundwater-associated salinity, and irrigation-induced salinity. There are several soil processes which lead to salt build-up in the root zone interfering with the growth and physiological functions of plants. Salts, depending on the ionic composition and concentration, can also affect many soil processes, such as soil water dynamics, soil structural stability, solubility of essential nutrients, and pH and pE of soil water—all indirectly hindering plant growth. The direct effect of salinity includes the osmotic effect affecting water and nutrient uptake and the toxicity or deficiency due to high concentration of certain ions. The plan of action to resolve the problems associated with soil salinization should focus on prevention of salt accumulation, removal of accumulated salts, and adaptation to a saline environment. Successful utilization of salinized soils needs appropriate soil and irrigation management and improvement of plants by breeding and genetic engineering techniques to tolerate different levels of salinity and associated abiotic stress.

Article

Soil Sediment Loading and Related Environmental Impacts from Farms  

Vito Ferro

Beyond damage to rainfed agricultural and forestry ecosystems, soil erosion due to water affects surrounding environments. Large amounts of eroded soil are deposited in streams, lakes, and other ecosystems. The most costly off-site damages occur when eroded particles, transported along the hillslopes of a basin, arrive at the river network or are deposited in lakes. The negative effects of soil erosion include water pollution and siltation, organic matter loss, nutrient loss, and reduction in water storage capacity. Sediment deposition raises the bottom of waterways, making them more prone to overflowing and flooding. Sediments contaminate water ecosystems with soil particles and the fertilizer and pesticide chemicals they contain. Siltation of reservoirs and dams reduces water storage, increases the maintenance cost of dams, and shortens the lifetime of reservoirs. Sediment yield is the quantity of transported sediments, in a given time interval, from eroding sources through the hillslopes and river network to a basin outlet. Chemicals can also be transported together with the eroded sediments. Sediment deposition inside a reservoir reduces the water storage of a dam. The prediction of sediment yield can be carried out by coupling an erosion model with a mathematical operator which expresses the sediment transport efficiency of the hillslopes and the channel network. The sediment lag between sediment yield and erosion can be simply represented by the sediment delivery ratio, which can be calculated at the outlet of the considered basin, or by using a distributed approach. The former procedure couples the evaluation of basin soil loss with an estimate of the sediment delivery ratio SDRW for the whole watershed. The latter procedure requires that the watershed be discretized into morphological units, areas having a constant steepness and a clearly defined length, for which the corresponding sediment delivery ratio is calculated. When rainfall reaches the surface horizon of the soil, some pollutants are desorbed and go into solution while others remain adsorbed and move with soil particles. The spatial distribution of the loading of nitrogen, phosphorous, and total organic carbon can be deduced using the spatial distribution of sediment yield and the pollutant content measured on soil samples. The enrichment concept is applied to clay, organic matter, and all pollutants adsorbed by soil particles, such as nitrogen and phosphorous. Knowledge of both the rate and pattern of sediment deposition in a reservoir is required to establish the remedial strategies which may be practicable. Repeated reservoir capacity surveys are used to determine the total volume occupied by sediment, the sedimentation pattern, and the shift in the stage-area and stage-storage curves. By converting the sedimentation volume to sediment mass, on the basis of estimated or measured bulk density, and correcting for trap efficiency, the sediment yield from the basin can be computed.

Article

Soils, Science, Society, and the Environment  

Colin R. Robins

Soils are the complex, dynamic, spatially diverse, living, and environmentally sensitive foundations of terrestrial ecosystems as well as human civilizations. The modern, environmental study of soil is a truly young scientific discipline that emerged only in the late 19th century from foundations in agricultural chemistry, land resource mapping, and geology. Today, little more than a century later, soil science is a rigorously interdisciplinary field with a wide range of exciting applications in agronomy, ecology, environmental policy, geology, public health, and many other environmentally relevant disciplines. Soils form slowly, in response to five inter-related factors: climate, organisms, topography, parent material, and time. Consequently, many soils are chemically, biologically, and/or geologically unique. The profound importance of soil, combined with the threats of erosion, urban development, pollution, climate change, and other factors, are now prompting soil scientists to consider the application of endangered species concepts to rare or threatened soil around the world.

Article

Soil Tilth and Management  

Lars J. Munkholm, Mansonia Pulido-Moncada, and Peter Bilson Obour

Soil tilth is a dynamic and multifaceted concept that refers to the suitability of a soil for planting and growing crops. A soil with good tilth is “usually loose, friable and well granulated”; a condition that can also be described as the soil’s having a good “self-mulching” ability. On the other hand soils with poor tilth are usually dense (compacted), with hard, blocky, or massive structural characteristics. Poor soil tilth is generally associated with compaction, induced by wheel traffic, animal trampling, and/or to natural soil consolidation (i.e., so-called hard-setting behavior). The soil-tilth concept dates back to the early days of arable farming and has been addressed in soil-science literature since the 1920s. Soil tilth is generally associated with soil’s physical properties and processes rather than the more holistic concepts of soil quality and soil health. Improved soil tilth has been associated with deep and intensive tillage, as those practices were traditionally considered the primary method for creating a suitable soil condition for plant growth. Therefore, for millennia there has been a strong focus both in practice and in research on developing tillage tools that create suitable growing conditions for different crops, soil types, and climatic conditions. Deep and intensive tillage may be appropriate for producing a good, short-term tilth, but may also lead to severe long-term degradation of the soil structure. The failure of methods relying on physical manipulation as means of sustaining good tilth has increased the recognition given to the important role that soil biota have in soil-structure formation and stabilization. Soil biology has only received substantial attention in soil science during the last few decades. One result of this is that this knowledge is now being used to optimize soil management through strategies such as more diverse rotations, cover crops, and crop-residue management, with these being applied either as single management components or more preferably as part of an integrated system (i.e., either conservation agriculture or organic farming).Traditionally, farmers have evaluated soil tilth qualitatively in the field. However, a number of quantitative or semi-quantitative procedures for assessing soil tilth has been developed over the last 80 years. These procedures vary from simply determining soil cloddiness to more detailed evaluations whereby soil’s physical properties (e.g., porosity, strength, and aggregate characteristics) are combined with its consistency and organic-matter measurements in soil-tilth indices. Semi-quantitative visual soil-evaluation methods have also been developed for field evaluation of soil tilth, and are now used in many countries worldwide.

Article

State of the Art of Contingent Valuation  

Tim Haab, Lynne Y. Lewis, and John Whitehead

The contingent valuation method (CVM) is a stated preference approach to the valuation of nonmarket goods. It has a 50+-year history beginning with a clever suggestion to simply ask people for their consumer surplus. The first study was conducted in the 1960s and over 10,000 studies have been conducted to date. The CVM is used to estimate the use and non-use values of changes in the environment. It is one of the more flexible valuation methods, having been applied in a large number of contexts and policies. The CVM requires construction of a hypothetical scenario that makes clear what will be received in exchange for payment. The scenario must be realistic and consequential. Economists prefer revealed preference methods for environmental valuation due to their reliance on actual behavior data. In unguarded moments, economists are quick to condemn stated preference methods due to their reliance on hypothetical behavior data. Stated preference methods should be seen as approaches to providing estimates of the value of certain changes in the allocation of environmental and natural resources for which no other method can be used. The CVM has a tortured history, having suffered slings and arrows from industry-funded critics following the Exxon Valdez and British Petroleum (BP)–Deepwater Horizon oil spills. The critics have harped on studies that fail certain tests of hypothetical bias and scope, among others. Nonetheless, CVM proponents have found that it produces similar value estimates to those estimated from revealed preference methods such as the travel cost and hedonic methods. The CVM has produced willingness to pay (WTP) estimates that exhibit internal validity. CVM research teams must have a range of capabilities. A CVM study involves survey design so that the elicited WTP estimates have face validity. Questionnaire development and data collection are skills that must be mastered. Welfare economic theory is used to guide empirical tests of theory such as the scope test. Limited dependent variable econometric methods are often used with panel data to test value models and develop estimates of WTP. The popularity of the CVM is on the wane; indeed, another name for this article could be “the rise and fall of CVM,” not because the CVM is any less useful than other valuation methods. It is because the best practice in the CVM is merging with discrete choice experiments, and researchers seem to prefer to call their approach discrete choice experiments. Nevertheless, the problems that plague discrete choice experiments are the same as those that plague contingent valuation. Discrete choice experiment–contingent valuation–stated preference researchers should continue down the same familiar path of methods development.

Article

State of the Art of Hedonic Pricing  

Dennis Guignet and Jonathan Lee

Hedonic pricing methods have become a staple in the environmental economist’s toolkit for conducting nonmarket valuation. The hedonic pricing method (HPM) is a revealed preference approach used to indirectly infer the value buyers and sellers place on characteristics of a differentiated product. Environmental applications of the HPM are typically focused on housing and labor markets, where the characteristics of interest are local environmental commodities and health risks. Despite the fact that there have been thousands of hedonic pricing studies published, applications of the methodology still often grapple with issues of omitted variable bias, measurement error, sample selection, choice of functional form, effect heterogeneity, and the recovery of policy-relevant welfare estimates. Advances in empirical methodologies, increased quality and quantity of data, and efforts to link empirical results to economic theory will surely further the use of the HPM as an important nonmarket valuation tool.

Article

Stormwater Management and Roadways  

Nigel Pickering and Somayeh Nassiri

Nonpoint source pollution is common in highly developed areas worldwide, degrading downstream water quality conditions and causing algal growth, aquatic toxicity, and sometimes fish kills. Stormwater runoff that results from rainfall or snowmelt events creates high-flow runoff from impervious surfaces and adjacent areas transporting multiple pollutants to the receiving waters. Although water quality regulations in the developed world have been effective in cleaning up wastewater discharges, their success with remediating stormwater discharges has not been consistent. An exploration of the sources, characteristics, and treatment of roadway runoff, a type of runoff that can be toxic and more difficult to manage because of the linear nature of the road network, is necessary. Since 1975, there have been more than 50 major roadway studies quantifying the sources and types of runoff contaminants like sediment, metals, inorganic salts, and organic compounds. Vehicle sources of pollutants are considered the most pernicious of all roadway contaminants, with brakes and tires being major sources. In the last decade, the leachate from tire wear particles has been linked to toxicity in coho salmon. Nonstructural stormwater management minimizes contamination by using source controls; for example, the elimination of almost all lead in automotive fuel has reduced roadway lead contamination significantly and the introduction of low-copper brake pads in the United States is expected to reduce roadway copper contamination over time. Structural stormwater management practices treat contaminated roadway runoff using small natural treatment systems; this is due in large part to the linear nature of roadways that makes larger regional systems more difficult. Since 2000, treatment performance has improved; however, there is still a great need for further improvement. Suggestions for treatment improvements include designing with low maintenance in mind; applying machine learning to the existing data; improving the understanding of road-land pollutant dynamics; using a transdisciplinary applied research approach to identify the means to improve treatment and reduce toxicity; improving the media used in treatment systems to enhance performance; improving structural strength of permeable pavement; and increasing implementation by facilitating ways to allow/encourage small, effective, and less costly alternatives.

Article

Stormwater Management at the Lot Level: Engaging Homeowners and Business Owners to Adopt Green Stormwater Infrastructure  

Anand D. Jayakaran, Emily Rhodes, and Jason Vogel

The Clean Water Act of 1972 was the impetus for stormwater management in the United States, followed by the need for many cities to comply with consent decrees associated with combined sewer overflows. With rapidly growing urban centers and the attendant increasing costs of managing stormwater with larger stormwater facilities, green stormwater infrastructure (GSI) was deemed a useful measure to distribute the management of stormwater across the landscape. The management of stormwater has evolved from simply removing it as quickly as it is generated in order to prevent flooding, to intentionally detaining stormwater on the landscape. Typically, low-frequency large events are detained in central stormwater holding facilities, while GSI is employed to manage smaller high-frequency events, slowing and treating stormwater on the landscape itself. Installing GSI close to the source of runoff production ensures that stormwater directed towards these facilities are small enough in volume, so as not to overwhelm these systems. Within these GSI systems, the natural assimilative capacity of soils and plants slows and breaks down many of the pollutants that are found in stormwater runoff. The requirement for a broad spatial distribution of GSI across the landscape necessitates an acceptance of these technologies, and the willingness of the managers of these urban landscapes to maintain these systems on a continual basis. The policies put in place to transfer the responsibility of stormwater management onto individual lot owners range from regulations imposed on those that develop the landscape for commercial and industrial purposes, to incentives offered to individual lot owners to install GSI practices for the first time on their properties. GSI is, however, not a silver bullet for all stormwater ills, and care has to be taken in how it is deployed in order not to exacerbate systemic environmental and racial inequities. A careful and considered adoption of GSI that includes the desires, values, and the needs of the community in conjunction with the environmental goals they are designed to address is critical.

Article

Subsurface Flow of Water in Soils and Geological Formations  

Gerrit de Rooij

Henry Darcy was an engineer who built the drinking water supply system of the French city of Dijon in the mid-19th century. In doing so, he developed an interest in the flow of water through sands, and, together with Charles Ritter, he experimented (in a hospital, for unclear reasons) with water flow in a vertical cylinder filled with different sands to determine the laws of flow of water through sand. The results were published in an appendix to Darcy’s report on his work on Dijon’s water supply. Darcy and Ritter installed mercury manometers at the bottom and near the top of the cylinder, and they observed that the water flux density through the sand was proportional to the difference between the mercury levels. After mercury levels are converted to equivalent water levels and recast in differential form, this relationship is known as Darcy’s Law, and until this day it is the cornerstone of the theory of water flow in porous media. The development of groundwater hydrology and soil water hydrology that originated with Darcy’s Law is tracked through seminal contributions over the past 160 years. Darcy’s Law was quickly adopted for calculating groundwater flow, which blossomed after the introduction of a few very useful simplifying assumptions that permitted a host of analytical solutions to groundwater problems, including flows toward pumped drinking water wells and toward drain tubes. Computers have made possible ever more advanced numerical solutions based on Darcy’s Law, which have allowed tailor-made computations for specific areas. In soil hydrology, Darcy’s Law itself required modification to facilitate its application for different soil water contents. The understanding of the relationship between the potential energy of soil water and the soil water content emerged early in the 20th century. The mathematical formalization of the consequences for the flow rate and storage change of soil water was established in the 1930s, but only after the 1970s did computers become powerful enough to tackle unsaturated flows head-on. In combination with crop growth models, this allowed Darcy-based models to aid in the setup of irrigation practices and to optimize drainage designs. In the past decades, spatial variation of the hydraulic properties of aquifers and soils has been shown to affect the transfer of solutes from soils to groundwater and from groundwater to surface water. More recently, regional and continental-scale hydrology have been required to quantify the role of the terrestrial hydrological cycle in relation to climate change. Both developments may pose new areas of application, or show the limits of applicability, of a law derived from a few experiments on a cylinder filled with sand in the 1850s.

Article

Subsurface (Tile) Agricultural Drainage  

Gary R. Sands, Srinivasulu Ale, Laura E. Christianson, and Nathan Utt

Agricultural (tile) drainage enables agricultural production on millions of hectares of arable lands worldwide. Lands where drainage or irrigation (and sometimes both) are implemented, generate a disproportionately large share of global agricultural production compared to dry land or rain-fed agricultural lands and thus, these water management tools are vital for meeting the food demands of today and the future. Future food demands will likely require irrigation and drainage to be practiced on an even greater share of the world’s agricultural lands. The practice of agricultural drainage finds its roots in ancient societies and has evolved greatly to incorporate modern technologies and materials, including the modern drainage plow, plastic drainage pipe and tubing, laser and GPS-guided installation equipment, and computer-aided design tools. Although drainage brings important agricultural production and environmental benefits to poorly drained and salt-affected arable lands, it can also give rise to the transport of nutrients and other constituents to downstream waters. Other unwanted ecological and hydrologic environmental effects may also be associated with the practice. The goal of this article is to familiarize the reader with the practice of subsurface agricultural drainage, the history and extent of its application, and the benefits commonly associated with it. In addition, environmental effects associated with subsurface drainage including hydrologic and water quality effects are presented, and conservation practices for mitigating these unwanted effects are described. These conservation practices are categorized by whether they are implemented in-field (such as controlled drainage) versus edge-of-field (such as bioreactors). The literature cited and reviewed herein is not meant to be exhaustive, but seminal and key literary works are identified where possible.

Article

Surface Irrigation  

Luis S. Pereira and José M. Gonçalves

Surface irrigation is the oldest and most widely used irrigation method, more than 83% of the world’s irrigated area. It comprises traditional systems, developed over millennia, and modern systems with mechanized and often automated water application and adopting precise land-leveling. It adapts well to non-sloping conditions, low to medium soil infiltration characteristics, most crops, and crop mechanization as well as environmental conditions. Modern methods provide for water and energy saving, control of environmental impacts, labor saving, and cropping economic success, thus for competing with pressurized irrigation methods. Surface irrigation refers to a variety of gravity application of the irrigation water, which infiltrates into the soil while flowing over the field surface. The ways and timings of how water flows over the field and infiltrates the soil determine the irrigation phases—advance, maintenance or ponding, depletion, and recession—which vary with the irrigation method, namely paddy basin, leveled basin, border and furrow irrigation, generally used for field crops, and wild flooding and water spreading from contour ditches, used for pasture lands. System performance is commonly assessed using the distribution uniformity indicator, while management performance is assessed with the application efficiency or the beneficial water use fraction. The factors influencing system performance are multiple and interacting—inflow rate, field length and shape, soil hydraulics roughness, field slope, soil infiltration rate, and cutoff time—while management performance, in addition to these factors, depends upon the soil water deficit at time of irrigation, thus on the way farmers are able to manage irrigation. The process of surface irrigation is complex to describe because it combines surface flow with infiltration into the soil profile. Numerous mathematical computer models have therefore been developed for its simulation, aimed at both design adopting a target performance and field evaluation of actual performance. The use of models in design allows taking into consideration the factors referred to before and, when adopting any type of decision support system or multicriteria analysis, also taking into consideration economic and environmental constraints and issues. There are various aspects favoring and limiting the adoption of surface irrigation. Favorable aspects include the simplicity of its adoption at farm in flat lands with low infiltration rates, namely when water conveyance and distribution are performed with canal and/or low-pressure pipe systems, low capital investment, and low energy consumption. Most significant limitations include high soil infiltration and high variability of infiltration throughout the field, land leveling requirements, need for control of a constant inflow rate, difficulties in matching irrigation time duration with soil water deficit at time of irrigation, and difficult access to equipment for mechanized and automated water application and distribution. The modernization of surface irrigation systems and design models, as well as models and tools usable to support surface irrigation management, have significantly impacted water use and productivity, and thus competitiveness of surface irrigation.

Article

Sustainable Coffee Production  

Sarada Krishnan

Coffee is an extremely important agricultural commodity, produced in about 80 tropical countries, with an estimated 125 million people depending on it for their livelihoods in Latin America, Africa, and Asia, with an annual production of about nine million tons of green beans. Consisting of at least 125 species, the genus Coffea L. (Rubiaceae, Ixoroideae, Coffeeae) is distributed in Africa, Madagascar, the Comoros Islands, the Mascarene Islands (La Réunion and Mauritius), tropical Asia, and Australia. Two species are economically important for the production of the beverage coffee, C. arabica L. (Arabica coffee) and C. canephora A. Froehner (robusta coffee). Higher beverage quality is associated with C. arabica. Coffea arabica is a self-fertile tetraploid, which has resulted in very low genetic diversity of this significant crop. Coffee genetic resources are being lost at a rapid pace due to varied threats, such as human population pressures, leading to conversion of land to agriculture, deforestation, and land degradation; low coffee prices, leading to abandoning of coffee trees in forests and gardens and shifting of cultivation to other more remunerative crops; and climate change, leading to increased incidence of pests and diseases, higher incidence of drought, and unpredictable rainfall patterns. All these factors threaten livelihoods in many coffee-growing countries. The economics of coffee production has changed in recent years, with prices on the international market declining and the cost of inputs increasing. At the same time, the demand for specialty coffee is at an all-time high. In order to make coffee production sustainable, attention should be paid to improving the quality of coffee by engaging in sustainable, environmentally friendly cultivation practices, which ultimately can claim higher net returns.

Article

Sustainable Management of Groundwater  

Stephen Foster and John Chilton

This chapter first provides a concise account of the basic principles and concepts underlying scientific groundwater management, and it then both summarises the policy approach to developing an adaptive scheme of management and protection for groundwater resources that is appropriately integrated across relevant sectors and assesses the governance needs, roles and planning requirements to implement the selected policy approach.