Assessment of uncertainties in a complex modeling chain for predicting reservoir sedimentation under changing climate

Abstract

Long-term predictions of reservoir sedimentation require an objective consideration of the preceding catchment processes. In this study, we apply a complex modeling chain to predict sedimentation processes in the Banja reservoir (Albania). The modeling chain consists of the water balance model WaSiM, the soil erosion and sediment transport model combination RUSLE-SEDD, and the 3d hydro-morphodynamic reservoir model SSIIM2 to accurately represent all relevant physical processes. Furthermore, an ensemble of climate models is used to analyze future scenarios. Although the capabilities of each model enable us to obtain satisfying results, the propagation of uncertainties in the modeling chain cannot be neglected. Hence, approximate model parameter uncertainties are quantified with the First-Order Second-Moment (FOSM) method. Another source of uncertainty for long-term predictions is the spread of climate projections. Thus, we compared both sources of uncertainties and found that the uncertainties generated by climate projections are 408% (for runoff), 539% (for sediment yield), and 272% (for bed elevation in the reservoir) larger than the model parameter uncertainties. We conclude that (i) FOSM is a suitable method for quantifying approximate parameter uncertainties in a complex modeling chain, (ii) the model parameter uncertainties are smaller than the spread of climate projections, and (iii) these uncertainties are of the same order of magnitude as the change signal for the investigated low-emission scenario. Thus, the proposed method might support modelers to communicate different sources of uncertainty in complex modeling chains, including climate impact models.

Temporal variation of braided intensity and morphodynamic changes in a regulated braided river using 2D modeling and satellite images

“…This is obtained using the acoustic backscatter signal from two side-looking H-ADCPs (Horizontal acoustic Doppler Current Profiler; 0.6 and 1.2 MHz). Nevertheless, these measurements are only available for water depths at the gauging station exceeding 1 m (Pesci et al, 2023). In addition, using the pebble count method in the focused area of this study, the substrate grain size distribution curve was measured in the field, describing the bed material by D 50 of 19 mm, the mean particle size of 25 mm, and the standard deviation of 1.49.…”

From global glacier modeling to catchment hydrology: bridging the gap with the WaSiM-OGGM coupling scheme

“…In this case, the annual glacier outputs generated from OGGM allow to perform model simulations starting at any desired year, hence overcoming dependence on observed outlines. Furthermore, the successful application of both models in water-scarce regions (examples of studies carried out with WaSiM can be found in Cornelissen et al, 2013;Idrissou et al, 2020;Pesci et al, 2023 andwith OGGM, in Dixit et al, 2021;Ross et al, 2023) encourages the use of the coupling scheme in such areas. As a changing climate may significantly impact water availability by the end of the century, the prediction of the catchment's hydrological response becomes crucial.…”