The integrated water cycle involves the movement of water among the ocean, atmosphere, land, biosphere, and cryosphere, including interactions with human activities. Understanding the effects of global change on the integrated water cycle—including its alterations, impacts, and interactions across scales—requires interdisciplinary and interagency approaches.
USGCRP’s Integrated Water Cycle Group (IWCG, or “the group”) coordinates research that will help us better understand the effects of global change on the water cycle and the impacts of those changes through collaborative, interdisciplinary approaches. The IWCG seeks to develop interagency approaches to advance fundamental understanding and produce actionable science and results related to the integrated water cycle. The group maintains a multi-scale, research-to-services perspective that connects agencies’ fundamental research and capabilities with applied research and efforts that ensure the scientific insights these produce are translated into actionable information communicated to decision-makers, ensuring close coupling and open lines of communication among the various research communities.
The IWCG seeks to:
Coordinate research relevant to understanding the integrated water cycle, how it changes in response to short-term and long-term perturbations, and the associated local, regional, and global impacts of those changes;
Advance capabilities and research infrastructure that support water cycle observation, modeling, and prediction skills at a range of scales; and
Develop approaches to apply and translate our understanding and inform decisions concerning resilience and water security, supporting USGCRP climate services initiatives.
The IWCG consists of federal agency representatives (from current USGCRP agencies and the broader federal landscape) and interested SGCR/SCS Principals. The group features four active workstreams: Integrated Hydro-Terrestrial Modeling (IHTM), which the Coasts Interagency Group co-hosts, Flood Risk Analysis and Projection, Global Precipitation Experiment (GPEX), and the U.S. Global Energy and Water Exchanges (GEWEX). IWCG members meet bimonthly to exchange the latest science, products, and programs with guest speakers from the U.S. federal and non-federal integrated water cycle science community. Example discussion topics include:
Assessing Drought in a Changing Climate by NOAA NIDIS and USDA Climate Hubs
FEMA’s Future of Flood Risk Data Initiative
USGS National Hydrologic Geospatial Fabric and National Hydrologic Model
Climate effects on federal hydropower and DOE assessment under the SECURE Water Act
Statistical and dynamic downscaling products for decision-relevant climate projections
Inland waters and carbon biogeochemistry
IWCG members also contributed to a Report to Congress for the long-term research and monitoring program on western U.S. hydroclimatology.
Integrated Hydro-Terrestrial Modeling (IHTM) Workstream
First initiated as a conceptual framework at a 2019 interagency community workshop, IHTM aims to advance national and regional capabilities and infrastructure for multi-agency data and simulation products that provide the basis for understanding and managing complex water-human systems at various scales.
USGCRP hosted the second IHTM workshop (IHTM 2.0) in 2023 for U.S. federal and non-federal scientists and managers. Access a summary of federal agency perspectives on the IHTM 2.0 workshop outcomes.
The workshop built on the 2019 IHTM and 2020 Coastal-IHTM community workshops and their subsequent reports by:
Providing updates on recently emerging IHTM capabilities and essential research gaps
Outlining IHTM community testbeds that facilitate joint work in collaborative efforts exploring critical challenges
Helping create a thriving community of practice to advance IHTM beyond the workshop
Potential community testbeds included integrated modeling experiments across the U.S. National, Mid-Atlantic, Upper Colorado River Basin, Great Lakes, and Gulf Coast/Mississippi regions, exploring issues such as water extremes, water quality, water use, and urbanization. The workshop aimed to help move the community from concepts to implementation and was oriented around a research-to-operations-to-research (R2O2R) framing.
The IHTM interagency workstream consolidates subsets of USGCRP’s IWCG and Coasts Interagency Group (CoastsIG) memberships, along with interested federal participants of the IHTM 2.0 workshop, to sustain engagements across agencies and enhance the momentum.
Flood Risk Analysis and Projection Workstream
The IWCG Flood Workstream supports a collaborative relationship among federal agencies to improve the nation's understanding of flood hazards and risks. The objective of the workstream is to increase coordination among agencies to close gaps and share knowledge/methodologies for addressing current and future conditions in inland flood estimates. The workstream emphasizes modeling needs to bridge top-down and bottom-up approaches. The success of the workstream will be measured by demonstrating increased shared awareness of existing federal efforts and developing evidence-based consensus recommendations for best practices.
Global Precipitation Experiment (GPEX) Workstream
The GPEX Workstream facilitates federal coordination supporting the international Global Precipitation Experiment (GPEX).
Under the IWCG’s US GEWEX initiative, the foundation of GPEX was first discussed in 2020 among USGCRP agencies to address the gaps in precipitation prediction. This project aims to take on the challenge of improving precipitation predictions worldwide, including polar and high-mountain regions. In late 2020, NOAA and DOE jointly held a workshop on precipitation processes and predictability, which, among other efforts, enhanced interagency participation in precipitation processes. In addition, there have been several US GEWEX, US CLIVAR, and USGCRP-IGIM discussions on precipitation predictability. In October 2023, GPEX was officially launched as a World Climate Research Programme (WCRP) Lighthouse Activity centered around the WCRP Years of Precipitation and associated science activities. For more information, please see the GPEX Science Plan on the WCRP website.
To foster coordinated U.S. agency interactions with the international GPEX community, the GPEX Workstream is administratively anchored at IWCG, inherently connected and coordinating with US GEWEX, as well as with IGIM, ObsIWG, IAIWG, and US CLIVAR. The GPEX Workstream welcomes participation across USGCRP and the broader federal family.
In December 2024, the GPEX Workstream hosted a workshop with WMO-WCRP colleagues between U.S. federal agency program managers and the international GPEX Science Steering Group.
U.S. GEWEX (Global Energy and Water Exchanges) Workstream
The USGCRP established the U.S. GEWEX workstream in September 2019. The workstream supports U.S. interagency efforts on federal water and energy cycle research that align scientifically with the GEWEX core project of the World Climate Research Programme. U.S. GEWEX facilitates the coordination of interagency activities within the IWCG through regular discussions and meetings of program managers from the various USGCRP agencies interested in science relevant to GEWEX. This workstream is chaired by two program managers (currently from NASA and DOE).
U.S. GEWEX undertakes interagency activities to enhance predictive understanding of the water cycle and energy fluxes of the changing Earth and global climate system, using satellite and surface-based observations, global and regional process-resolving models, and the resulting diagnostics and data. The focus on water cycle and energy exchange is predominantly on multiscale atmospheric processes and surface-atmosphere interactions at various scales, including phenomena such as local recycling of water, moisture transport, cloud-precipitation interactions, and changes to radiative balance.
The U.S. GEWEX workstream supports activities that address scientific objectives, including (but not limited to) understanding and prediction of current and future water cycle extremes; land-atmosphere interactions; the role of clouds in a changing water cycle; teleconnections between water cycle phenomena and changes in other parts of the Earth system (e.g., how changes in the Arctic may affect mid-latitude storms); and the impacts of large scale human-Earth system interactions (e.g., land management and irrigation) on regional and global water cycles.
Select U.S. GEWEX Activities
NOAA-DOE Precipitation Processes and Predictability Workshop
Our ability to predict when, where, and how much precipitation will fall is critical for decision-making and responding to the impacts of extreme rainfall across a wide range of sectors and timescales. The current generation of Earth system models (ESMs), however, have large and persistent systematic errors that severely limit the ability to faithfully reproduce the many spatial and temporal scales of precipitation variability.
The NOAA-DOE Precipitation Predictability and Processes Workshop was held virtually during November 30−December 2, 2020. In partnership with USGCRP and the U.S. Climate Variability and Predictability Program (US CLIVAR), the workshop was attended by participants from the observational and modeling research communities as well as operational centers to address the challenge of precipitation predictability. More specifically, the workshop focused on precipitation predictability and physical processes for the contiguous United States with an emphasis on sub-seasonal to multi-decadal timescales. Essentially, the workshop asked how we can improve our ability to predict precipitation variability and extremes.
Learn more in the joint workshop report announcements by DOE and NOAA.
Global Precipitation Experiment (GPEX)
The Global Precipitation Experiment (GPEX) was proposed by USGCRP and established in 2022 as a World Climate Research Programme (WCRP) Lighthouse Activity to bring the international weather, water, and climate communities together to improve precipitation science and prediction at different time scales: weather, sub-seasonal-to-seasonal, interannual, and decadal. GPEX will leverage existing WCRP programs and community capabilities in observations, modeling, and research. It will also conduct new activities to fill gaps in observing and understanding precipitation processes and accelerate progress in improving predictions and their applications. Member agencies of the U.S. GEWEX workstream and USGCRP’s International Activities Interagency Group will facilitate coordination with WCRP to explore opportunities to advance GPEX.
Hydroclimate Activities
U.S. GEWEX is engaged in several active or planned topics on hydroclimatology. These efforts include but are not limited to
a two-part mini-workshop on soil moisture from 2021 (see below)
a proposed mini-workshop on ecohydrology
a proposed mini-workshop on extreme events, particularly flash droughts
regional hydroclimate topics, such as mountainous hydroclimate studies and solutions
engagements with the Humans and Hydroclimate in the United States (H2US) GEWEX Affinity Group.