Integrated modeling in urban hydrology: reviewing the role of monitoring technology in overcoming the issue of ‘big data’ requirements

Increasingly, the application of models in urban hydrology has undergone a shift toward integrated structures that recognize the interconnected nature of the urban landscape and both the natural and engineered water cycles. Improvements in computational processing during the past few decades have enabled the application of multiple, connected model structures that link previously disparate systems together, incorporating feedbacks and connections. Many applications of integrated models look to assess the impacts of environmental change on physical dynamics and quality of landscapes. Whilst these integrated structures provide a more robust representation of natural dynamics, they often place considerable data requirements on the user, whereby data are required at contrasting spatial and temporal scales which can often transcend multiple disciplines. Concomitantly, our ability to observe complex, natural phenomena at contrasting scales has improved considerably with the advent of increasingly novel monitoring technologies. This has provided a pathway for reducing model uncertainty and improving our confidence in modeled outputs by implementing suitable monitoring regimes. This commentary assesses how component models of an exemplar integrated model have advanced over the past few decades, with a critical focus on the role of monitoring technologies that have enabled better identification of the key physical process. This reduces the uncertainty of processes at contrasting spatial and temporal scales, through a better characterization of feedbacks which then enhances the utility of integrated model applications

Doctor of Philosophy

dissertationAs one of the most important earth systems, the water cycle is significantly disrupted by changes to land cover and water management accompanying urbanization. Recently, researchers have developed a concept of near-natural hydrology to guide ecological engineering of urban systems to mitigate the impacts of development on the water cycle. Stormwater green infrastructure (GI) is one of the practices that has been used to restore the urban hydrology. The goal of this research is to answer the overarching question: Can GI implemented in a semiarid watershed restore the water budget to its predevelopment condition? Field experiments and hydrologic modeling were conducted in a semiarid city, Salt Lake City, Utah, U.S to answer this question. This work created, for the first time, an ET observation dataset for the semiarid intermountain west of the U.S. Based on the new dataset, empirical parameters for Penman-Monteith ET methods, including crop coefficients and surface resistances for green roofs, were identified and calibrated for this region, also for the first time. Their values can be directly used for ET modeling of green roofs in similar climates. An urban stormwater model, EPA SWMM, was modified to be able to represent spatially heterogeneous ET rates in one catchment for up to six types of land covers, including GI (bioretention, green roof), landscapes (turf, deciduous trees, coniferous trees), and water surface. This creates an improved platform to study the hydrologic response of urban watersheds by addressing the limitation of hydrologic models, not including GI and stormwater models with poor representation of ET. Also, the EPA SWMM was modified to be able to operate using subdaily ET time series input for the first time. With the updated model, the final part of this work studies the potential of restoring the predevelopment urban water budget by adopting GI strategies in a semiarid watershed. Based on the proposed water budget restoration coefficient, the water budgets have been restored due to GI applications 94%, 94%, and 82% of the predevelopment state in the dry, average, and wet years, respectively

Improving water network management by efficient division into supply clusters

El agua es un recurso escaso que, como tal, debe ser gestionado de manera eficiente. Así, uno de los propósitos de dicha gestión debiera ser la reducción de pérdidas de agua y la mejora del funcionamiento del abastecimiento. Para ello, es necesario crear un marco de trabajo basado en un conocimiento profundo de la redes de distribución. En los casos reales, llegar a este conocimiento es una tarea compleja debido a que estos sistemas pueden estar formados por miles de nodos de consumo, interconectados entre sí también por miles de tuberías y sus correspondientes elementos de alimentación. La mayoría de las veces, esas redes no son el producto de un solo proceso de diseño, sino la consecuencia de años de historia que han dado respuesta a demandas de agua continuamente crecientes con el tiempo. La división de la red en lo que denominaremos clusters de abastecimiento, permite la obtención del conocimiento hidráulico adecuado para planificar y operar las tareas de gestión oportunas, que garanticen el abastecimiento al consumidor final. Esta partición divide las redes de distribución en pequeñas sub-redes, que son virtualmente independientes y están alimentadas por un número prefijado de fuentes. Esta tesis propone un marco de trabajo adecuado en el establecimiento de vías eficientes tanto para dividir la red de abastecimiento en sectores, como para desarrollar nuevas actividades de gestión, aprovechando esta estructura dividida. La propuesta de desarrollo de cada una de estas tareas será mediante el uso de métodos kernel y sistemas multi-agente. El spectral clustering y el aprendizaje semi-supervisado se mostrarán como métodos con buen comportamiento en el paradigma de encontrar una red sectorizada que necesite usar el número mínimo de válvulas de corte. No obstante, sus algoritmos se vuelven lentos (a veces infactibles) dividiendo una red de abastecimiento grande.Herrera Fernández, AM. (2011). Improving water network management by efficient division into supply clusters [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/11233Palanci

Assessing vulnerability and modelling assistance: using demographic indicators of vulnerability and agent-based modelling to explore emergency flooding relief response

Flooding is a significant concern for much of the UK and is recognised as a primary threat by most local councils. Those in society most often deemed vulnerable: the elderly, poor or sick, for example, often see their level of vulnerability increase during hazard events. A greater knowledge of the spatial distribution of vulnerability within communities is key to understanding how a population may be impacted by a hazard event. Vulnerability indices are regularly used – in conjunction with needs assessments and on-the-ground research – to target service provision and justify resource allocation. Past work on measuring and mapping vulnerability has been limited by a focus on income-related indicators, a lack of consideration of accessibility, and the reliance on proprietary data. The Open Source Vulnerability Index (OSVI) encompasses an extensive range of vulnerability indicators supported by the wider literature and expert validation and provides data at a sufficiently fine resolution that can identify vulnerable populations. Findings of the OSVI demonstrate the potential cascading impact of a flood hazard as it impacts an already vulnerable population: exacerbating pre-existing vulnerabilities, limiting capabilities and restricting accessibility and access to key services. The OSVI feeds into an agent-based model (ABM) that explores the capacity of the British Red Cross (BRC) to distribute relief during flood emergencies using strategies based upon the OSVI. A participatory modelling approach was utilised whereby the BRC were included in all aspects of the model development. The major contribution of this work is the novel synthesis of demographics analysis, vulnerability mapping and geospatial simulation. The project contributes to the growing understanding of vulnerability and response management within the NGO sector. It is hoped that the index and model produced will allow responder organisations to run simulations of similar emergency events and adjust strategic response plans accordingly

Modelización del transporte de contaminantes en redes de saneamiento urbano

A pesar de que, en términos generales, la forma disuelta de los contaminantes suele ser más tóxica y más reactiva química y biológicamente, el impacto de la forma particulada resulta más significativo a largo plazo debido a su capacidad de acumulación y a su capacidad de actuar como una fuente secundaria de contaminantes disueltos. Por tal motivo, se ha considerado fundamental incluir la dinámica de los sólidos en suspensión puesto que la contaminación de sedimentos es considerada por varios organismos ambientales internacionales como el mayor riesgo en los ambientes acuáticos. En consecuencia, la predicción del transporte, erosión y deposición de los sedimentos es una labor de suma importancia para el entendimiento de las características de la calidad de las aguas. No obstante, debe tenerse presente que aunque la introducción de un mayor número de variables en el modelo permite realizar un análisis más preciso, requiere también de una mayor cantidad de información para alimentarlo. Las zonas de costa soportan una fuerte presión antrópica debida, principalmente, a la rápida industrialización y el aumento poblacional, lo cual, se traduce en fuentes de contaminación representadas por descargas de efluentes domésticos e industriales. Tal es el caso, por ejemplo, de la Ría de Huelva en la que, además de la presión que representa la propia actividad industrial y portuaria, los vertidos mineros y la erosión de terrenos piríticos acidifican las aguas más lejanas al mar permitiendo que los metales se mantengan en forma disuelta. El objetivo principal de este trabajo ha sido presentar un modelo simplificado para predecir la tasa de transporte de sedimentos en las tuberías de alcantarillado unitario. La distribución del tamaño de partícula y la densidad de partículas son factores muy significativos en los modelos de transporte. Varía dependiendo de la ubicación del alcantarillado y la fuente de contaminantes. En este sentido, se ha llevado a cabo un análisis de sensibilidad de la tasa de transporte y los perfiles de concentración en tuberías. El modelo que se presenta resulta de la integración de dos modelos. De un lado el Modelo de Gestión de Aguas Residuales (SWMM) de la EPA, y de otro, la incorporación a este primero del modelado del transporte de sedimentos en el interior de las conducciones del sistema de saneamiento. Esta incorporación complementa y enriquece el análisis de la red solventando la limitación del software de la EPA de no simular la propagación de contaminantes en el flujo subsuperficial, es decir, dentro de las conducciones, una vez el flujo de escorrentía entra al sistema de saneamiento.Although the dissolved form of pollutants is generally more toxic and more reactive chemically and biologically, the impact of the particulate form is more significant in the long term because of its accumulation capacity and its capacity to act as a secondary source of dissolved contaminants. For this reason, it has been considered essential to include the dynamics of suspended solids since sediment contamination is considered by several international environmental organisms as the greatest risk in aquatic environments. Consequently, prediction of sediment transport, erosion and deposition is an extremely important task in understanding the characteristics of water quality. However, it should be borne in mind that although the introduction of a greater number of variables in the model allows for a more precise analysis, it also requires a greater amount of information to feed it. The coastal zones bear strong anthropic pressure due mainly to rapid industrialization and population increase, which translates into pollution sources represented by domestic and industrial effluent discharges. This is the case, for example, of the Ria de Huelva in which, in addition to the pressure of industrial and port activity itself, mining spills and the erosion of pyritic terrains acidify the waters further away from the sea by allowing metals are maintained in dissolved form. The main aim of this work is to present a simplified model to predict the sediment transport rate in combined sewer pipe. Particle size distribution and particle density are very significant factors in transport models. It varies in function of the sewer location and pollutant source. A sensitivity analysis of the transport rate and concentration profiles in pipes has been conducted in this study. The model presented results from the integration of two models. On the one hand, the EPA's Wastewater Management Model (SWMM), and on the other, the simplified model to predict the sediment transport rate in combined sewer pipe. This integration complements and enriches the network analysis by solving the EPA's software limitation of not simulating the propagation of contaminants in the subsurface flow, i.e. within the pipelines, once the runoff flow enters the sanitation system. As well as other predictive models allow to obtain information for the analysis of the temporal and spatial distribution of the emissions to the environment, essential tool as support to the decision making to improve the control of the intermittent contamination by discharges of unitary systems. You can also obtain information on load patterns that arrive at a sewage plant or a holding tank at the start of a storm event, allowing for more rational resource planning

Water management in the developing town: a complex systems perspective

Provision of water services is a critical strategy for addressing worldwide poverty, and this is one of the most pressing challenges of current times and is linked to population growth and climate change. Progress has been slow in achieving even the Millennium Development Goals aimed at improving coverage of adequate water services and professionals are struggling to cope with the diversity and scale of situations. Water services provision is a context-dependent process and many types of situations are very challenging, such as that of small developing towns. This thesis addresses the problems of urban centres in Pacific Island Countries and the aim is to provide formal explanations of difficulties in these locations to support recommendations that recognize local constraints and opportunities to best practice management. This is achieved largely by employing a perspective based on the science of Complex Adaptive Systems. This perspective has been chosen in recognition that water management incorporates complex interactions between social, technical and natural systems. The research is case study based, focusing primarily on Tarawa in the Pacific Island nation of Kiribati. The methodology includes historical review of the case study, and the use of historical review, as well as interviews and observation in the field as well as a cross-cutting email-based Delphi survey. This has generated qualitative and quantitative data to allow for the formulation of scientific models, an Agent Based Model describing the complex interactions involved in water service delivery; and Bayesian Network models describing the factors impacting on the chances of successful management interventions. With improved explanation of the complex situation, this has been used to support the formulation of a strategic and adaptive governance framework; aiming to introduce much needed organisational memory, and a consistent strategic direction set on the basis of the effective stakeholder interaction. By recognising weakness in capacity, it is possible to turn these into strengths by building and utilising local knowledge and commitment.Pascal Pere

Modelling an urban water system on the edge of chaos

Viewing an urban water system as a complex adaptive system provides new opportunities for analysis and avoids some critical simplifications. Taking this perspective, it is possible to explore the inter-related effects of changes to the system. This is particularly important in the developing world where donors providing aid aim to improve conditions but struggle to understand and quantify the systemic impacts of their actions. This is because an intervention aiming to improve condition may also have unintended and undesirable effects. To provide decision support, this paper describes an agent-based model of an urban water system, developed on the basis of ethnographic interviews, and subsequently evaluated by local stakeholders. The paper describes the model design as well as the results of scenarios. The model provides guidance on which system amendments may produce the best outcomes in terms of output variables, and on the basis of sense-checking and sensitivity analysis it is judged that model results are likely to give a good indication about possible real world outcomes. It is clear that no single strategy will solve all problems on its own, but that a combined strategy e with a strong focus on groundwater management and protection e is likely to be most successful. (Résumé d'auteur

Modelling an urban water system on the edge of chaos

Viewing an urban water system as a complex adaptive system provides new opportunities for analysis and avoids some critical simplifications. Taking this perspective, it is possible to explore the inter-related effects of changes to the system. This is particularly important in the developing world where donors providing aid aim to improve conditions but struggle to understand and quantify the systemic impacts of their actions. This is because an intervention aiming to improve condition may also have unintended and undesirable effects. To provide decision support, this paper describes an agent-based model of an urban water system, developed on the basis of ethnographic interviews, and subsequently evaluated by local stakeholders. The paper describes the model design as well as the results of scenarios. The model provides guidance on which system amendments may produce the best outcomes in terms of output variables, and on the basis of sense-checking and sensitivity analysis it is judged that model results are likely to give a good indication about possible real world outcomes. It is clear that no single strategy will solve all problems on its own, but that a combined strategy - with a strong focus on groundwater management and protection - is likely to be most successful