The New England Water-Use Data System (NEWUDS) is a database for the storage and retrieval of water-use data. NEWUDS can handle data covering many facets of water use, including (1) tracking various types of water-use activities (withdrawals, returns, transfers, distributions, consumptive-use, wastewater collection, and treatment); (2) the description, classification and location of places and organizations involved in water-use activities; (3) details about measured or estimated volumes of water associated with water-use activities; and (4) information about data sources and water resources associated with water use. In NEWUDS, each water transaction occurs unidirectionally between two site objects, and the sites and conveyances form a water network. The core entities in the NEWUDS model are site, conveyance, transaction/rate, location, and owner. Other important entities include water resources (used for withdrawals and returns), data sources, and aliases. Multiple water-exchange estimates can be stored for individual transactions based on different methods or data sources. Storage of user-defined details is accommodated for several of the main entities. Numerous tables containing classification terms facilitate detailed descriptions of data items and can be used for routine or custom data summarization. NEWUDS handles single-user and aggregate-user water-use data, can be used for large or small water-network projects, and is available as a stand-alone Microsoft? Access database structure. Users can customize and extend the database, link it to other databases, or implement the design in other relational database applications.