Hydrologic and other environmental scientists are beginning to use commercial database technologies to locate, assemble, analyze, and archive data. A data model that is both capable of handling the diversity of data and simple enough to be used by non-database professionals remains an open question. Over the past three years, we have been working in parallel on data models with hydrologists of Consortium of Universities for the Advancement of Hydrologic Science Inc. (CUAHSI) and Berkeley Water Center (BWC). This report proposes a new data model with learning from both efforts. This new model has major improvements in spatial support, namespace translation, provenance tracking and versioning, extensibility, and supports a wide array of data types. We have used this data model to build a hydrologic data catalog server (http://www.sciscope.org) containing metadata for over 358 million sensor and point sample measurements.