Hydrological Evaluation of the Grid-to-Grid Model on the Upper Murray Catchment

Moore, Robert; Cole, S.J.; Mattingley, P.S.; Wells, S.C.; Robson, A.J.; Black, K.B.; Davies, H.; Bell, V.A.

Hydrological Evaluation of the Grid-to-Grid Model on the Upper Murray Catchment

Moore, Robert; Cole, S.J.; Mattingley, P.S.; Wells, S.C.; Robson, A.J.; Black, K.B.; Davies, H.; Bell, V.A. ORCID: https://orcid.org/0000-0002-0792-5650. 2014 Hydrological Evaluation of the Grid-to-Grid Model on the Upper Murray Catchment. Wallingford, UK, Centre for Ecology & Hydrology, 76pp.

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Abstract/Summary

This document reports the experience of the first application of the G2G model for water forecasting in Australia through a pilot case study for the Upper Murray catchment. G2G (Grid-to-Grid) is a physical-conceptual grid-based distributed hydrological model used by environment agencies in Britain to support flood guidance at countrywide scale. Its area-wide formulation allows G2G to provide real-time flow forecasts everywhere on a 1km model grid and thus is particularly well suited for application to areas that are ungauged. This is achieved through use of a model formulation that is underpinned by spatial datasets on terrain, land-cover and soil/geology properties. These landscape properties act to shape a storm pattern into a flow response providing a coherent space-time map of river flows and their evolution from flood to drought conditions. Depending on application, G2G can be configured for a range of model domains (catchment, river basin, regional, national, global) and grid-resolutions (from 50 m through 1 km and 25 km have been used). The Bureau of Meteorology (Australia) has an interest in using G2G for water forecasting at a range of time-scales: for flood and short-term forecasting (up to 7 days), seasonal forecasting (up to a few months), and for long-term water availability predictions (decadal and climate change time scales). Exploring the potential value of G2G in these application contexts, and with a focus on the short-term forecasting time-scales initially, is the main purpose of this Upper Murray catchment pilot study. The report provides background to the G2G model and its use in the UK whilst four appendices provide additional information on applications of potential relevance to the Bureau of Meteorology. The challenges of setting up G2G using the spatial datasets available for Australia are discussed in some detail as part of configuring the Upper Murray G2G prototype. An approach to model setup, calibration and assessment is developed that is tailored to the hydrometric network of the Upper Murray and the impact of the Dartmouth Reservoir control. The performance of the G2G model is first assessed in simulation-mode, with a focus on how well G2G transforms gridded rainfall and potential evaporation to river flow. The performance of G2G in forecast-mode using full data assimilation (a combination of state-updating, direct flow insertion and error-prediction) of river flows is then assessed. Performance is better at locations upstream of the reservoir and best for the Mitta Mitta at Hinnomunjie with annual R2 Model Efficiencies up to 0.74 in simulation-mode and exceeding 0.9 when upstream gauged flows are assumed known. Degraded performance occurs in areas of steep rainfall gradients and sparsely located raingauges. The forecast-mode assessment shows how performance varies with lead-time and the dependence on rainfall forecasts is illustrated using “zero rainfall” and “perfect foreknowledge of raingauge rainfall” input scenarios. The step-change in capability deriving from use of a distributed hydrological model, giving a gridded river flow forecast output, is illustrated via a prototype visualisation of forecast flood rarity/severity. This is based on a colour-coding of the maximum return-period exceedance for each G2G pixel. The maps give a strong visual indication of the relative flow severity across different areas and how these evolve over time. The report closes with a summary of achievements along with recommendations - both of a research and operational nature - that aim to help the Bureau of Meteorology in its future planning of G2G applications in Australia.

Item Type:

Publication - Report (Project Report)

UKCEH and CEH Sections/Science Areas:

Reynard

Funders/Sponsors:

Australian Government Bureau of Meteorology

Additional Keywords:

Distributed hydrological model, water forecasting, flood, drought, G2G, Upper Murray

NORA Subject Terms:

Hydrology

Date made live:

28 Nov 2025 16:06 +0 (UTC)