8. Water Quality and Ecosystem Modelling: Practical Application on Lakes and Reservoirs

Impacts of anthropogenic and other pressures on lakes and reservoirs are often a subject of detailed analyses, which can be aimed, e.g. to identify causes of the water quality deterioration or changes in ecosystems and to predict effects of projects likely to have significant effects on the environment. Since the mid-nineteenth century, such analyses were increasingly supported by an application of mathematical models, which are nowadays capable of 3-dimensional, high-resolution simulation of complex interactions in water bodies, including fluid dynamics, heat transfer and biogeochemical reactions. Mathematical models, until recently perceived as an innovative approach or a good practice, quickly became a legally required element of water management procedures. This chapter presents five examples of the application of aquatic ecosystem models in Poland. Applications were selected in such a way, as to represent various case studies differentiated not only by characteristics of the water body and its catchment area but also by the goal of the model application. Examples include reservoirs with the surface area ranging from 0.1 to 32 km² and catchment areas ranging from 13 to more than 500 km². Presented applications were either a part of research projects or studies commissioned by local authorities. Aims of presented studies include among others a presentation of real-time status of the water body, analyses of impacts of reservoir and catchment management scenarios, an evaluation of the recreational potential, an evaluation of planned remedial measures and support to the state environmental monitoring system.