The Effect of Riparian Zones on Nitrate Removal by Denitrification at the River Basin Scale : CRC Press : 9781138024052 : 1138024058 : 14 May 2014 : At the interface between terrestrial and aquatic ecosystems, the riparian zone plays an important role in nitrogen removal, despite the minor proportion of the land area that it covers. Very limited studies are carried out in modelling these effects at the river basin scales. The Soil and Water Assessment Tool (SWAT) is a well-known river basin scale model to simulate hydrological processes and nutrient dispersal. So far, SWAT followed a lumped approach that did not take into account the effect of the particular position of the hydrological units and their interaction, which implied that SWAT could not model riparian zones as discrete units and take into account the effects from upland areas. This thesis presents two modifications in SWAT: (i) an approach to represent landscape variability and landscape routing across different landscape u