Book excerpt: Draws on data collected over a network of sites representing Britain's major wetland types, revealing similarities in the response of wetlands to climate and other influences. Introduces important factors of wetland hydrology that must be taken into account for the purpose of water management and the evaluation of numerous threats to wetlands. As an indication of what can be achieved through the use of more up-to-date technology, the author describes the quantification of the wetland water budget using a computer-controlled lysimeter.