Water Resources

Abstract

When forecasting the availability of water in a catchment or region, many factors may need to be considered, such as the influence of reservoirs, lakes, inter-basin transfer schemes, groundwater storage, and urban drainage, together with water demands from a range of users. Whilst in some applications, such as flood forecasting, smaller influences can sometimes be ignored, for water resources applications they may need to be considered in some detail. Forecasting techniques include integrated catchment modelling approaches which combine rainfall-runoff and flow routing models, supply-demand models which consider the balance between water supply and demand from a range of users, and regional, continental or global scale distributed models (which are sometimes called macroscale models). Increasingly water quality and ecological components are also included, and the role of atmospheric chemistry is also considered in climate change impact studies. Given this complexity, a toolkit approach is often used for model development, building models from the components which are required to represent the key features of the systems under consideration. For longer timescales, but increasingly also for medium- and short-term forecasting, probabilistic techniques are also used to estimate the sensitivity of results to the assumptions which are made. Data assimilation is also important in many applications, particularly for shorter lead times. This chapter presents an introduction to these various topics, and also briefly discusses some of the forecasting requirements for river basin management, integrated water resources management, and water resources planning and management.