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220The second option might appear coarse, especially with one or two tributariesas lateral inflows: the actual contribution from these sub-catchments may beexcessively increased by the scaling factor, resulting in unbalanced simulationsover the river reach. However, eliminating uniformly distributed inflows doesnot leave many options to properly reproduce the distribution of inflows along225the river reach with a defined number of injections. As a result, the second op-tion should be regarded here as a comparative reference rather than a reliablesolution in coupling RR and hydraulic models.tel-00392240, version 1 - 5 Jun 2009230235The spatial aggregation of lateral inputs constitutes the second importantaspect investigated in this study: for each option presented previously, thenumber of contributions coming from tributaries in the form of point lateralinflow is gradually increased from 1 to 6. Figure 3 shows the first four discretisationlevels. Tributaries are considered by decreasing order of catchment sizeat the confluence with the main channel, as shown in Figure 1.b. The rationalebehind this ordering is to start with the main lateral contribution and to progressivelyrefine the definition of point lateral inflows. Of course, catchmentsize may poorly reflect the magnitude of contributions from the tributaries,as small catchments with impermeable soils may bring more water than largeones. This point will be discussed in Section 5.2.240Note that the simulations at the Kansas station cannot be calculated by thecoupled model when the configuration does not explicitly include tributaryno. 2 as a point inflow. Kansas is located near the catchment outlet of thistributary; the simulation at this point is then conditioned by the existence ofthe corresponding contribution.12