This document forms a supplement to the report “A Wetland Framework for Impact Assessment at Statutory Sites in England and Wales” by B.D. Wheeler and S.C. Shaw, which presents the results of investigations into the inter-relationships between water source, water quantity, water quality and vegetation type in sites supporting herbaceous wetland vegetation in lowland England and Wales. The core of the Wetland Framework is a typology of the main ecohydrological units that occur within lowland herbaceous wetlands in England and Wales, based on a synthesis of the available data and analysis results. 20 Wetland Water Supply Mechanisms (WETMECs) have been identified and described, along with the Ecological Types that are associated with them. In combination, the WETMECs and Ecological Types define ecohydrological ‘habitats’. This document provides a synopsis of the WETMECs and their characteristics, and can be used as a stand-alone document.