Development of a routing procedure to assist an earth systems model with long term coastal discharge predictions

Abstract

Nearest neighbour searches, scaling, and a flow accumulation method were applied to improve predictions for freshwater deposits from land surfaces to the ocean for an earth systems model. Runoff, generated by the Conformal Cubic Atmospheric Model (CCAM), was read at a coarse resolution and downscaled, whereas digital elevation- and accumulation values were obtained from the HydroSHEDS database and upscaled. The accumulation, digital elevation, and runoff values were matched using a KDTree nearest neighbour algorithm. Starting from a zero-valued initial water body, CCAM runoff was routed to neighbouring cells. Flow direction was determined with a maximum flow accumulation method whereas the Manning equation was used to calculate the discharge rate. Inland reservoirs and coastal waters were removed and added to an outflow term. Mass conservation checks confirmed that the proposed procedure conserves mass and a 25-year simulation shows that the relative discharge rates, river routes, and outflow locations were sufficiently predicted.