Business and scientific case for the development of an object-oriented groundwater model

A new technology is set to transform the development and capabilities of models used for hydrological simulation. The approach is rapidly becoming popular because it enables applications to be developed that incorporate a high degree of complexity but which are accurate, easily modifiable, and easy to use, in addition to having a clear structure. The approach is that of the object-oriented paradigm. Object-orientation offers the potential to solve many of the problems associated with existing modelling tools, which are used for the assessment and management of the water environment. The major benefit of the approach is that it enables applications to be developed which focus on physical processes and mechanisms. That is, it is now realistic to envisage the development of models that are constructed around hydrological or hydrogeological features. It should no longer be considered acceptable to ‘fit’ engineering problems into the fixed frameworks of current models. Tools can now be developed that enable user’s to investigate processes rather than just being able to define parameter values. The core principle of object-oriented model development is the reproduction of real-world features as computational equivalents. For example, considering a number of scales, aquifers, river catchments, wetlands or pumped wells could be defined as objects, each containing a complex but well defined behaviour. In particular, wetlands are generally simulated inadequately in existing models. Compared to current techniques it would be relatively straightforward to incorporate a number of different conceptual models of wetlands and detailed wetland processes in an object-oriented model. Whilst object-orientation is a method for developing models, the approach offers major benefits to hydrogeological and hydrological simulation and management. This document presents a business and scientific case for the development of an object-oriented groundwater model. The objective of the work is to develop a high quality, publicly available piece of modelling software which simulates regional groundwater systems but which provides a platform for the eventual development of an integrated model of the hydrological cycle. The central principle of the development is to focus on physical processes. That is, to identify hydrogeological features or mechanisms which are represented inadequately, or not at all, in current models and then to construct computational equivalents. These will be incorporated into the overall object-oriented hydrogeological/hydrological model framework. The development of the model incorporates three important objectives. First, the resulting model must be as good as existing groundwater models. Second, central to the model development is the goal of developing a tool that enables the simulation of hydrogeological features that are dealt with inadequately in existing groundwater models. Finally, the resulting model must be widely applicable to the management of UK groundwater and surface-water resources considering the prominent environmental management issues of the next twenty years. The model development will address: • The accurate numerical representation of conceptual hydrogeological models with the objective of developing models that closely resemble hydrogeological systems instead of adopting the current approach of fitting hydrogeological understanding to the restricted structure of groundwater models. • The detailed representation of wetlands with regard to the accurate simulation of aquifer- wetland interaction and the impact of groundwater abstraction of surface water flows. • The accurate simulation of groundwater abstraction and rivers at the local scale within a regional context. The need to develop tools to accurately analyse the impact of abstraction on rivers, for example within Catchment Abstraction Management Strategies, to improve ii the evaluation of abstraction licence applications and source protection zones, to accurately simulate pumped wells, well fields and artificial recharge schemes and to model river- aquifer interaction at the channel scale is central to the philosophy of the model development. • The development of a user-friendly GIS based recharge model, which is fully integrated with the groundwater model. • The development of an integrated object-oriented solute transport model for the simulation of contaminant transport in UK aquifers, for example, with regard to transport in dual porosity media such as the Chalk. • The utilisation of the benefits of novel computing technology for the development of user- friendly hydrogeological modelling and management tools. A prototype groundwater model has been developed which represents a first attempt at designing and implementing a framework of objects, which accurately represents the structure of common hydrogeological features within a regional groundwater model. The development of the model has been achieved through the collaboration of The Environment Agency, The British Geological Survey and The University of Birmingham. This has brought about the opportunity to steer the progress of modelling both within the UK and internationally. The recognition of the benefits of object-orientation by the project group is timely. The approach offers the potential to integrate tools for the simulation and management of water resources, water quality and ecology with the framework of the hydrological cycle. This project represents the beginning of that process but will significantly advance our ability to model, understand and manage the water environment