Methodology (including best practice guidelines) on how to identify and incorporate ‘concentrated’ and ‘distributed’ run-off in pre-operational forecasts, based on the input and requirements from our users

摘要

In coastal scale oceanographic models, land boundary discharges have a significant impact on the water quality assessment and prediction. In this report the state of the art methodology to identify and incorporate continental run-off, including both the distributed (urban) and point wise (rivers) run-off, into coastal scale oceanographic models is described. After this general methodology, the application of this theory to the Catalan coast case study is described. This demonstrates how the theory can be applied but also shows which results can be obtained with which uncertainty. The Catalan Coast case study was chosen for this purpose because local (torrential) rainfall is considered to have a high impact on the quality of coastal waters and it is thus important to be able to predict the land discharge adequately such that it can be incorporated into the coastal scale oceanographic models. From this application it can be concluded that high temporal resolution data is important for an accurate prediction of the high extreme discharges and that also more water quality measurements/information are desirable. It has been shown that using conceptual models to predict the freshwater input into oceanographic models is a good approach as reasonably accurate results can be obtained with short calculation times, an important prerequisite for an operational model. In contrast to the highly temporally variable Catalan coast region, Liverpool Bay is considered as a second test case. This area is a region of freshwater influence (ROFI) and the Bay is both horizontally and laterally stratified by the inflow from several rivers. As the Bay is affected by the presence of freshwater year-round, river climatologies are presently used, so there is scope for improvement, including more accurate fluxes, distributed run-off and real-time river data. The freshwater inflow at the Wadden Sea and Gulf of Venice case study is also considered to be very important and is already included into the oceanographic model as a lateral forcing in the respective hydrodynamic models. Currently, measured or climatological data are being used for the purpose which is presently sufficient for the pre-operational model that is run.