Flow Control

Abstract

The runoff response of a catchment is often modified by the influence of river control structures, reservoirs and other factors, such as urban drainage systems. In hydrometeorological forecasting applications, these artificial influences can cause flows to be delayed, attenuated, and otherwise modified from the natural response. The extent to which these effects need to be considered varies with the application; for example, in flood forecasting applications, the flow releases from a reservoir for ecological purposes might be relatively insignificant, although would probably be relevant in a drought forecasting application. The influence also varies with scale so that, for example, urban influences might sometimes be relatively minor at a catchment scale, but important at a local level in terms of the impacts on river flows and water quality. This chapter discusses a range of techniques for forecasting the impacts of flow control structures on river flows, under the main headings of river structures, reservoirs, and urban drainage. In many cases, the operating strategy will be governed by a set of control rules, based either on off-line studies, or optimised in real-time, and sometimes implemented using a decision support system. A brief introduction is also provided to decision support and real-time control systems of this type.