HYDRUS is a Windows-based modeling software package that can be used to analyze water flow and heat and solute transport in variably saturated porous media (e.g., soils or the vadose zone). The HYDRUS software includes an interactive graphics-based interface for data preprocessing, soil profile discretization, and graphic presentation of the results. Historically, HYDRUS consisted of two independent software packages. While HYDRUS-1D simulated flow and transport processes in one dimension and was a public domain software, HYDRUS (2D/3D; and earlier HYDRUS-2D) extended the simulation capabilities to the second and third dimensions and was distributed commercially. These two previously independent software packages were merged in 2023 into a single software package called HYDRUS.
The capabilities of the HYDRUS software packages have been significantly expanded by various standard and nonstandard specialized add-on modules. The standard add-on modules are fully incorporated and supported by the HYDRUS graphical user-friendly interfaces (GUIs) and documented in detail in the technical and user manuals. This is not the case for several additional nonstandard modules, which require additional work outside the GUI. A commonality of all HYDRUS add-on modules is that they simulate variably saturated water flow and heat and solute transport in porous media. The specialized add-on modules provide additional capabilities, such as considering general reactive transport (in the HPx models) or reactive transport with specific chemistry (notably the Wetland and UNSATCHEM modules). Other modules provide additional flow and/or transport modeling processes, such as to account for preferential flow (the DualPerm module), colloid-facilitated solute transport (the C-Ride module), or the transport of polyfluoroalkyl substances (PFAS; the PFAS module) or fumigant (the Fumigant module) compounds.
The HYDRUS models are among the most widely used numerical models for simulating processes in the subsurface. There are many thousands of HYDRUS users worldwide, with many applications (also several thousand) appearing in peer-reviewed international literature and many technical reports.
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Article
The Family of HYDRUS Models
Jiří Šimůnek, Giuseppe Brunetti, Martinus Th. van Genuchten, and Miroslav Šejna
Article
Ecosystem Benefits of Large Dead Wood in Freshwater Environments
Ellen Wohl
Large wood in freshwater environments is downed, dead wood pieces in river channels, floodplains, wetlands, and lakes. Large wood was historically much more abundant in freshwaters, but decades to centuries of deforestation and direct wood removal have decreased wood loads—volumes of large wood per unit area—in freshwaters around the world. The widespread public perception that large wood is undesirable in freshwater environments contrasts with scientific understanding of the beneficial effects of large wood. Large wood tends to increase the spatial heterogeneity of hydraulics, substrate, channel planform, and the floodplain and hyporheic zone in rivers. This equates to greater habitat diversity and refugia for organisms, as well as energy dissipation and storage of materials during floods, which can increase the resilience of the river to disturbances such as wildfire, drought, and flooding. Similarly, wood in lakes increases lakeshore and lakebed heterogeneity of hydraulics, substrate, habitat, nutrient uptake, and storage of particulate organic matter and sediment. Large wood in rivers and lakes provides an array of vital ecosystem functions, and both individual species and biotic communities are adversely affected by a lack of wood in rivers and lakes that have been managed in a way that reduces wood loads. River and lake management are now more likely to include protection of existing large wood and active reintroduction of large wood, but numerous questions remain regarding appropriate targets for wood loads in different environmental settings, including potential threshold wood loads necessary to create desired effects. Large wood can also directly and indirectly enhance carbon storage in freshwater environments, but this storage remains poorly quantified.
Article
Politics of Local Community Engagement in Transboundary Water Negotiations
Isabela Espindola and Pilar Villar
The sharing of transboundary water resources, whether surface or groundwater, is a significant challenge, both in theory and practice. Countries in situations of sharing these natural resources are predisposed to interact with each other. These interactions, here called transboundary water interactions, are characterized by the coexistence of cooperation and conflict, which can arise at different governance levels. However, negotiations around transboundary water resources primarily occur between diplomats and high government members from riparian countries and river basin organization (RBO) managers. Transboundary water negotiations are usually considered high-level political discussions, given the complexity and scale of the water challenges. Consequently, decision-making processes incorporate only a limited number of participants, who make decisions capable of impacting the entire population that depend on the shared waters. Over the last 20 years, there has been a need for greater transparency and a participatory process in transboundary water negotiations, especially for local community engagement and collaboration in these processes. Many of the negotiation processes around transboundary water resources need the participation of municipalities and local populations, concomitant with the involvement of RBOs, to carry out decisions to manage transboundary waters in an integrated manner. There are several reasons for this demand, including negotiation effectiveness, contestation prevention, data sharing, ensuring continuing participation and collaboration, and promoting public awareness related to water resources. Discussing social participation, particularly in the management of transboundary water resources, requires attention to the historical context and its constraints. Considering the enormous challenge, the experiences of local community engagement in transboundary water negotiations in South America, especially from the Guarani Aquifer and the La Plata Basin, are good examples for improving this discussion around transboundary water interactions and local community engagement. The La Plata Basin is the second-largest transboundary basin in the continent, shared by Argentina, Bolivia, Brazil, Uruguay, and Paraguay, while the Guarani Aquifer is one of the largest reservoirs of freshwater worldwide, shared by Argentina, Brazil, Paraguay, and Uruguay. Even with both having cooperation agreements in place between the riparian states, there are still great difficulties with regard to the participation of local communities in transboundary water negotiations.
Article
Environmental Humanities and Italy
Enrico Cesaretti, Roberta Biasillo, and Damiano Benvegnú
Does something like “Italian environmental humanities” exist? If so, what makes an Italian approach to this multifaceted field of inquiry so different from the more consolidated Anglo-American tradition?
At least until the early 21st century, Italian academic institutions have maintained established disciplinary boundaries and have continued to produce siloed forms of knowledge. New and more flexible forms of scholarly collaboration have also not been traditionally supported at the national level, as political decisions regarding curricular updates and funding opportunities have been unable to foster interdisciplinarity and innovative approaches to knowledge production.
However, an underlying current of environmental awareness and action has a strong and long-standing presence in Italy. After all, Italy is where St. Francis wrote The Canticle of Creatures, with its non-hierarchical vision of the world, which then inspired the papal encyclical Laudato si (2015). Italy is also where Ambrogio Lorenzetti’s fresco The Allegory and the Effects of Good Government in the City and in the Country (1337–1339) already “pre-ecologically” reflected on the relationship between nature and culture, on the effect of political decisions on our surroundings, and on the impact of local environments on the well-being (as well as the malaise) of their inhabitants. Additionally, Italy is among the few countries in the world whose constitution lists specific laws aimed at protecting its landscapes, biodiversity, and ecosystems in addition to its cultural heritage, as stated in a recent addendum to articles 9 and 41.
However, Italy also experienced an abrupt, violent process of development, modernization, and industrialization that radically transformed its urban, rural, and coastal territories after World War II. Many of its landscapes, once iconic and picturesque, have become polluted, toxic, or the outcome of contested, violent histories. And the effects of globalization are materially affecting its ecologies, meaning that Italy is also exposed to constant risks (earthquakes, floods, landslides, volcanic eruptions) and presents geo-morphological features that situate it at the very center of planetary climate change (both atmospheric and sociopolitical) and migration patterns. Considering this, thinking about Italy from an environmental humanities (EH) perspective and, in turn, about the EH in the context of Italy, highlights the interconnections between the local and the global and, in the process, enriches the EH debate.
Article
Bioeconomic Models
Ihtiyor Bobojonov
Bioeconomic models are analytical tools that integrate biophysical and economic models. These models allow for analysis of the biological and economic changes caused by human activities. The biophysical and economic components of these models are developed based on historical observations or theoretical relations. Technically these models may have various levels of complexity in terms of equation systems considered in the model, modeling activities, and programming languages. Often, biophysical components of the models include crop or hydrological models. The core economic components of these models are optimization or simulation models established according to neoclassical economic theories. The models are often developed at farm, country, and global scales, and are used in various fields, including agriculture, fisheries, forestry, and environmental sectors. Bioeconomic models are commonly used in research on environmental externalities associated with policy reforms and technological modernization, including climate change impact analysis, and also explore the negative consequences of global warming. A large number of studies and reports on bioeconomic models exist, yet there is a lack of studies describing the multiple uses of these models across different disciplines.
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Economics of Climate Change Adaptation
Babatunde O. Abidoye
To view climate change adaptation from an economic perspective requires a definition of adaptation, an economic framework in which to view adaptation, and a review of the literature on specific adaptations (especially in agriculture). A focus on tools for applying adaptation to developing countries highlights the difference between mitigation and the adaptation decision-making process. Mitigation decisions take a long-term perspective because carbon dioxide lasts for a very long time in the atmosphere. Adaptation decisions typically last the lifespan of the investments, so the time frame depends on the specific adaptation investment, but it is invariably short compared to mitigation choices, which have implications for centuries. The short time frame means that adaptation decisions are not plagued by the same uncertainty that plagues mitigation choices. Finally, most adaptation decisions are local and private, whereas mitigation is a global public decision. Private adaptation will occur even without large government programs. Public adaptations that require government assistance can mainly be made by existing government agencies. Adaptation does not require a global agreement.
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
The Role of Tourism in Sustainable Development
Robert B. Richardson
Sustainable development is the foundational principle for enhancing human and economic development while maintaining the functional integrity of ecological and social systems that support regional economies. Tourism has played a critical role in sustainable development in many countries and regions around the world. In developing countries, tourism development has been used as an important strategy for increasing economic growth, alleviating poverty, creating jobs, and improving food security. Many developing countries are in regions that are characterized by high levels of biological diversity, natural resources, and cultural heritage sites that attract international tourists whose local purchases generate income and support employment and economic development. Tourism has been associated with the principles of sustainable development because of its potential to support environmental protection and livelihoods. However, the relationship between tourism and the environment is multifaceted, as some types of tourism have been associated with negative environmental impacts, many of which are borne by host communities.
The concept of sustainable tourism development emerged in contrast to mass tourism, which involves the participation of large numbers of people, often in structured or packaged tours. Mass tourism has been associated with economic leakage and dependence, along with negative environmental and social impacts. Sustainable tourism development has been promoted in various ways as a framing concept in contrast to these economic, environmental, and social impacts. Some literature has acknowledged a vagueness of the concept of sustainable tourism, which has been used to advocate for fundamentally different strategies for tourism development that may exacerbate existing conflicts between conservation and development paradigms. Tourism has played an important role in sustainable development in some countries through the development of alternative tourism models, including ecotourism, community-based tourism, pro-poor tourism, slow tourism, green tourism, and heritage tourism, among others that aim to enhance livelihoods, increase local economic growth, and provide for environmental protection. Although these models have been given significant attention among researchers, the extent of their implementation in tourism planning initiatives has been limited, superficial, or incomplete in many contexts.
The sustainability of tourism as a global system is disputed among scholars. Tourism is dependent on travel, and nearly all forms of transportation require the use of non-renewable resources such as fossil fuels for energy. The burning of fossil fuels for transportation generates emissions of greenhouse gases that contribute to global climate change, which is fundamentally unsustainable. Tourism is also vulnerable to both localized and global shocks. Studies of the vulnerability of tourism to localized shocks include the impacts of natural disasters, disease outbreaks, and civil unrest. Studies of the vulnerability of tourism to global shocks include the impacts of climate change, economic crisis, global public health pandemics, oil price shocks, and acts of terrorism. It is clear that tourism has contributed significantly to economic development globally, but its role in sustainable development is uncertain, debatable, and potentially contradictory.
Article
Urban Heat Islands and Their Associated Impacts on Health
Clare Heaviside
Towns and cities generally exhibit higher temperatures than rural areas for a number of reasons, including the effect that urban materials have on the natural balance of incoming and outgoing energy at the surface level, the shape and geometry of buildings, and the impact of anthropogenic heating. This localized heating means that towns and cities are often described as urban heat islands (UHIs). Urbanized areas modify local temperatures, but also other meteorological variables such as wind speed and direction and rainfall patterns. The magnitude of the UHI for a given town or city tends to scale with the size of population, although smaller towns of just thousands of inhabitants can have an appreciable UHI effect. The UHI “intensity” (the difference in temperature between a city center and a rural reference point outside the city) is on the order of a few degrees Celsius on average, but can peak at as much as 10°C in larger cities, given the right conditions. UHIs tend to be enhanced during heatwaves, when there is lots of sunshine and a lack of wind to provide ventilation and disperse the warm air. The UHI is most pronounced at night, when rural areas tend to be cooler than cities and urban materials radiate the energy they have stored during the day into the local atmosphere.
As well as affecting local weather patterns and interacting with local air pollution, the UHI can directly affect health through heat exposure, which can exacerbate minor illnesses, affect occupational performance, or increase the risk of hospitalization and even death. Urban populations can face serious risks to health during heatwaves whereby the heat associated with the UHI contributes additional warming. Heat-related health risks are likely to increase in future against a background of climate change and increasing urbanization throughout much of the world. However, there are ways to reduce urban temperatures and avoid some of the health impacts of the UHI through behavioral changes, modification of buildings, or by urban scale interventions. It is important to understand the physical properties of the UHI and its impact on health to evaluate the potential for interventions to reduce heat-related impacts.
Article
Changes in Land Use Influenced by Anthropogenic Activity
Lang Wang and Zong-Liang Yang
The terms “land cover” and “land use” are often used interchangeably, although they have different meanings. Land cover is the biophysical material at the surface of the Earth, whereas land use refers to how people use the land surface. Land use concerns the resources of the land, their products, and benefits, in addition to land management actions and activities. The history of changes in land use has passed through several major stages driven by developments in science and technology and demands for food, fiber, energy, and shelter.
Modern changes in land use have been increasingly affected by anthropogenic activities at a scale and magnitude that have not been seen. These changes in land use are largely driven by population growth, urban expansion, increasing demands for energy and food, changes in diets and lifestyles, and changing socioeconomic conditions. About 70% of the Earth’s ice-free land surface has been altered by changes in land use, and these changes have had environmental impacts worldwide, ranging from effects on the composition of the Earth’s atmosphere and climate to the extensive modification of terrestrial ecosystems, habitats, and biodiversity. A number of different methods have been developed give a thorough understanding of these changes in land use and the multiple effects and feedbacks involved. Earth system observations and models are examples of two crucial technologies, although there are considerable uncertainties in both techniques. Cross-disciplinary collaborations are highly desirable in future studies of land use and management. The goals of mitigating climate change and maintaining sustainability should always be considered before implementing any new land management strategies.
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