G2G predicts river flows and floods due to rainfall. It is used by researchers and operational agencies for real-time flood forecasting from days to seasons ahead, for climate change assessments, and for long-term simulations and scenarios.
G2G is a distributed, grid-based hydrological model used to predict river flows across regional, national and continental scales at both gauged and ungauged locations. It can be configured to a range of spatial scales from 50m upwards, on Cartesian or latitude-longitude grids, and is commonly applied at a 1km scale. It makes full use of gridded time-series data on rainfall. G2G uses spatial datasets on terrain, soil/geology and land-cover to represent variability in flood response to storm rainfall across grid-cell, catchment, river basin, state and country domains. It can include effects on river flow caused by artificial influences such as abstractions/discharges and reservoirs/lakes. A snow hydrology module and data assimilation of observed river flows are also available. In contrast to more complex distributed hydrological and land surface models, the physical-conceptual form of G2G employs depth-integrated formulations of runoff production and flow routing, and is therefore computationally efficient: countrywide real-time flood forecasting on a 1 km model grid is produced within 10 minutes. G2G can be linked to other models: it forms the core of HMF (see separate entry) and is a key component of the Flood Forecasting Centre's Surface Water Flooding (SWF) Hazard Impact Model (HIM) used for real-time forecasting of surface water impacts. G2G is used for real-time probabilistic flood forecasting using ensemble precipitation forecasts and can provide other outputs including: water quantity and quality; relative wetness/dryness of catchments; and seasonal Hydrological Outlooks.
G2G was originally developed from 2002 for UK flood forecasting. It has since been applied internationally and for many other applicatons (climate impacts, water resources, drought modelling, seasonal forecasting).
Whereas grid-based hydrological (and land-surface) models are widely used internationally, G2G is specifically developed for UK conditions using UK-available datasets to improve UK flood forecasting capability. And, while Environment Agency regional models can typically forecast up to 2 days ahead, G2G can forecast up to 5 days ahead across the whole UK. G2G can also be adapted for overseas applications.
G2G was developed by UKCEH with commissioning partners to meet their operational needs: Environment Agency; EA-Met Office Flood Forecasting Centre; Scottish Environment Protection Agency (SEPA); Scottish Flood Forecasting Service (SFFS); Australian Bureau of Meteorology.
Use of the G2G model is restricted to licensed users: Environment Agency; Scottish Environmental Protection Agency (SEPA); Australian Bureau of Meteorology; Met Office weather and climate service partnership for SE Asia (WCSSP). Many G2G outputs are freely available via the UKCEH Environmental Information Data Centre (EIDC) and other UKCEH data portals.
Development and application of G2G was funded by many users and sources including: Environment Agency-Met Office Flood Forecasting Centre (FFC: covers England and Wales); Scottish Environment Protection Agency (SEPA); Scottish Flood Forecasting Service (SFFS); Australian Bureau of Meteorology (BoM); Met Office Weather and Climate Science for Service Partnership for SE Asia (WCSSP); and UKRI-NERC National Capability programmes (Hydro-JULES; UK-SCAPE).
G2G is used by: operational flood forecasting services for England, Wales and Scotland (FFC; EA; SFFS; SEPA) providing probabilistic flood impact forecasts in real-time and out to 5 days; UK flood and environmental agencies (providing monthly Hydrological Outlooks and climate change assessments); Australian Bureau of Meteorology (providing annual water quantity and quality assessments as part of Great Barrier Reef health report card); WCSSP (India programme); wider research community and water industry (through collaboration with UKCEH).