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Environmental models are used extensively to evaluate the effectiveness of a range of design, planning, operational, management and policy options. However, the number of options that can be evaluated manually is generally limited, making it difficult to identify the most suitable options to consider in decision-making processes. By linking environmental models with evolutionary and other metaheuristic optimization algorithms, the decision options that make best use of scarce resources, achieve the best environmental outcomes for a given budget or provide the best trade-offs between competing objectives can be identified. This Introductory Overview presents reasons for embedding formal optimization approaches in environmental decision-making processes, details how environmental problems are formulated as optimization problems and outlines how single- and multi-objective optimization approaches find good solutions to environmental problems. Practical guidance and potential challenges are also provided.

Summary Baseflow is often considered to be the groundwater discharge component of streamflow. It is commonly estimated using conceptual models, recursive filters or a combination of the two. However, it is difficult to validate these methods due to the current challenges of measuring baseflow in the field. In this study, simulation of a synthetic catchment’s response to rainfall is carried out using a fully integrated surface water-groundwater flow model. A series of rainfall events with differing recovery periods and varied antecedent moisture conditions is considered to span a range of different streamflow generation dynamics. Baseflow is estimated for the outlet hydrograph of the synthetic catchment using a selection of commonly used automated baseflow separation methods. These estimates are compared to the baseflow signal obtained from the numerical model, which serves as the control experiment. Results from these comparisons show that depending on the method used, automated baseflow separation underestimates the simulated baseflow by as much as 28%, or overestimates it by up to 74%, during rainfall events. No separation method is found to be clearly superior to the others, as the performance of the various methods varies with different soil types, antecedent moisture conditions and rainfall events. The differences between the various approaches clearly demonstrate that the baseflow separation methods investigated are not universally applicable.

The understanding of streamflow generation processes is vitally important in the management of water resources. In the absence of the data required to achieve this, Integrated Surface-Subsurface Hydrological Models (ISSHM) can be used to assist with the development of this understanding. However, the standard outputs from these models only enable elicitation of information about hydrological drivers and hydrological responses that occur at the same time. This generally limits the applicability of ISSHMs for the purposes of obtaining an improved understanding of streamflow generation processes to catchment areas that do not exhibit significant storage, travel times or flow depletion mechanisms. In order to overcome this limitation, a previously published Hydraulic Mixing-Cell (HMC) method is improved so that it can be used to follow surface water derived from direct rainfall and groundwater discharge to the stream and adjacent overland flow areas. The developed approach was applied to virtual experiments (based on the Lehstenbach catchment in southeastern Germany), which are composed of two ISSHMs of contrasting scales: (1) a riparian wetland of area 210 m2 and (2) a catchment of area 4.2 km2. For the two models, analysis of modeling results for a large storm event showed complex spatiotemporal variability in streamflow generation and surface water-groundwater interaction. Further analysis with the HMC method elucidated in-stream and overland flow generation mechanisms. This study showed within a modeling framework that identification and quantification of in-stream and overland flow generation better informed understanding of catchment functioning through decomposition of streamflow hydrographs, and analysis of spatiotemporal variability of flow generation mechanisms.

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Challenges facing urban planners and governments continue to mount as populations in urban areas increase, pressure on the world's resources reaches critical levels and degradation of ecosystems around the world becomes increasingly apparent. The movement towards sustainable development has been met with enthusiasm by decision-makers, although exactly how to achieve this target, or even measure progress towards it, is not entirely evident. This paper explores how complex urban systems can be modelled holistically using a multi-agent based framework, and their sustainability assessed using a systems approach. There are numerous subsystems and corresponding resources (natural, financial, human and man-made) within an urban development such as water, energy, transport, waste, economic and social systems. All of these subsystems and their interrelations can be modelled using multi-agent systems, along with effects of human behaviour, both spatially and temporally, in order to provide planners, developers and decision-makers with a better platform for understanding the complexities of the urban form. As well as the presentation of a general overview of how the complexities of urban systems can be best captured using integrated modelling techniques such as multi-agent systems, the AUSTIME methodology, Assessment of Urban Sustainability Through Integrated Modelling and Exploration, will be briefly presented. This methodology is designed to show how quantifiable sustainability assessment, based on system resource thresholds, and multi-agent based modelling, can be integrated into a framework that can be used for decision making and management relating to policy, regulation, planning, design and development of urban systems. The framework is designed to form part of a cyclic process, such as an adaptive management and learning or total quality management cycle that can explicitly include stakeholder participation and ongoing evaluation. Specific examples of the implementation of this methodology are provided from a case study of Christie Walk, an eco-development in inner-city Adelaide, Australia. The case study involves the development of a prototype multi-agent based model coupled with a sustainability assessment framework that allows quantifiable sustainability comparisons for a range of indicators between the Christie Walk development and the larger Adelaide metropolitan area. Simulation results show that the ecodevelopment performs significantly better than the majority of Adelaide metropolitan developments, specifically in carbon dioxide production, where the development's occupants rate below the 5th percentile of all Adelaide residents. The model is subsequently used to examine scenarios relating to changes in occupant behaviour, development infrastructure and location. Simulations comparing the relative impacts of car ownership and use behaviour, and infrastructure design changes (where air conditioners and heaters are required to regulate indoor temperatures), show that high in-house electricity use behaviour related to infrastructure changes to Christie Walk could have a greater effect on equivalent carbon dioxide production than increased car ownership and use (potentially due to a location change to an outer suburb of the Adelaide metropolitan area). This result is just one example that highlights the necessity for planners and governments to consider the relative importance and effects of all subsystems in urban areas on the overall system's sustainability before attempting to design and choose management options and plans. It is envisaged that the AUSTIME methodology and case study application will help provide an example of how integrated modelling and sustainability assessment can be built into adaptive management cycles and effectively used as a decision making tool to work towards the sustainable development of urban environments and their inhabitants