River discharge datasets for the coastlines of Scotland and Northern Ireland

Cole, S.J.; Moore, R.J.; Davies, H.N.. 2014 River discharge datasets for the coastlines of Scotland and Northern Ireland. Wallingford, NERC/Centre for Ecology & Hydrology, 34pp. (CEH Project no. C04830) (Unpublished)

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Abstract/Summary

Marine Scotland has commissioned Halcrow to provide a “Hydrodynamic model of Scottish shelf waters”. The overall aim of the project is to provide modelling evidence that can support planning of marine renewables and aquaculture within the Scottish shelf waters. Subsequently, the Centre for Ecology & Hydrology (CEH) has been commissioned by Marine Scotland to provide river discharge datasets for the coastlines of Scotland and Northern Ireland. Their supply is the subject of this report. The overall project is structured to include validation runs of the hydrodynamic shelf water model against observations of oceanographic quantities as well as producing climatic runs based on climatological forcing. Several detailed case study areas from across the Scottish shelf waters are also to be considered: these include Pentland Firth and Orkney Waters (PFOW), Loch Linnhe, Lewis and Harris, and St Magnus Bay, Shetland. A key component to the success of any hydrodynamic shelf water modelling approach is the availability of robust estimates of freshwater river discharges along the relevant coastal boundaries: in this case Scotland and Northern Ireland. In particular, successfully capturing the freshwater and sea water mixing process within the approach is important to achieve the salinity modelling objectives of the project. Observed river flows based on the river gauging station network operated by the Scottish Environment Protection Agency (SEPA) are considered as one source of data. However, there are limitations in the spatial and temporal coverage of this gauging network: in particular, Northern Ireland is not included. This leaves considerable “ungauged” areas that require some form of hydrological modelling in order to provide the coastal river discharges needed by the shelf water models. The Grid-to-Grid (G2G) distributed rainfall-runoff and routing model developed by CEH has been chosen to help provide the coastal river discharge datasets. G2G is already used for real-time flood forecasting across Great Britain at gauged and ungauged locations and has been extensively calibrated and assessed against river gauging station data. Although G2G is not currently used operationally over Northern Ireland, it was judged that the existing model configuration could be readily transferred based on experience of a previous transfer from England & Wales to Scotland. This is because the model formulation is underpinned by spatial datasets on soil, land-cover, geology and terrain for the chosen model domain. For long-term climatological simulations and for periods when observed flows are not available, G2G can be run in “simulation-mode” where gridded rainfall and potential evaporation (PE) time-series are converted into modelled river flows. For more recent periods when river flow data are available over Scotland, G2G can make full use of these data via “direct flow insertion”. This serves to route the available gauged river flows downstream whilst modelling any river flow contributions from ungauged areas using rainfall and PE inputs. This report initially reviews the background to the G2G model and its operational application across Scotland for the Scottish Flood Forecasting Service. Then a summary of the G2G model transfer to Northern Ireland is presented. The methodology used to specify the river discharge locations is outlined along with details of the river discharge datasets delivered. Datasets are supplied meeting the needs of both the climatological and validation runs of the Scottish shelf water hydrodynamic model.

Item Type:	Publication - Report
UKCEH and CEH Sections/Science Areas:	Reynard
Funders/Sponsors:	CH2M HILL, Marine Scotland
Additional Information. Not used in RCUK Gateway to Research.:	Contract report to Marine Scotland under the project "Hydrodynamic model of Scottish shelf waters".
Additional Keywords:	hydrology, climatology, aquaculture, marine renewables, ocean modelling, shelf waters
NORA Subject Terms:	Meteorology and Climatology Hydrology Earth Sciences
Date made live:	18 Mar 2015 13:02 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/510192

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