Urban Developer: A model architecture for manageably building urban water cycle models spanning multiple scales

Abstract

Urban Developer is a flexible and modular modelling environment for the simulation of urban water cycle services systems (potable water supply, stormwater, and wastewater). It enables the simulation of these systems at a range of spatial and temporal scales within a single framework and has been developed to facilitate an improved understanding of the potential of integrated water cycle management strategies. Based on urbanCycle, the framework was designed to meet the objectives of scalability, ease of use, and complexity system management. The Urban Developer software application is built on the TIME framework and shares core functionality with the eWater Source IMS. This paper discusses the four key software features of the Urban Developer framework that have been implemented to meet the stated design objectives. These are the implementation of: a dynamic node-link network editing canvas, a parameter 'styles' management system, support for nested or "layered" networks, and an adaptive time-stepping engine. Urban Developer allows the linking together of water service components through the means of a node-link network. Each node in the network visually represents a system component, backed by a hydrological model of that component. Connection points corresponding to the water inputs and outputs are automatically added to each node. The components are connected by dragging a link from an output connector of a node to an input connector of another node, allowing the network to be rapidly built and easily visualised. With many instances of the same hydrological models, there is a large number of parameters to configure. This is managed by giving users the ability to create a new system component using an existing set of parameters as a template. This links the parameter set to the model, so changes to multiple identical models can be made simultaneously. To manage spatial complexity, a network can be nested in another network as a subnetwork node. This allows lower level details of the network to be hidden from high level views, and allows common network structures such as allotments to be built once and reused many times. The different temporal scale needs of the models are allowed for by a system of adaptive timestepping. When simulating periods of rainfall, short term response and thus fine simulation is required, while during dry periods only coarse simulation is required and thus the system clock is adjusted to a longer timestep. Processes are modeled coarsely where such a time scale is adequate, with inputs coming from finer scale models being automatically aggregated. While the timesteps used can be configured, the process is automatic, based on rainfall. The Urban Developer Beta has enjoyed a high level of adoption and received much positive feedback. Additionally, developers on related eWater projects have commenced integrating some of the mentioned Urban Developer features into those other tools, showing some demand for them.