Sediment load under diverse climate change scenarios

Description

Climate change directly affects the intensity of surface erosion and the sediment load in rivers. Currently, there are many climate models in use in Europe, and their forecasts differ to some extent. This means that the selection of models and their ensembles in environmental analyzes will directly translate into the predicted sediment load, which is important for mitigating the siltation of rivers and dammed reservoirs. Using the SWAT model [1,2,3], we performed research on the impact of adopting various climate models [4] on the sediment load flowing into the dammed reservoir. We included three types of comparison: A. We adopted point forecasts for the nearest large city – Kraków [5] and areal forecasts for the catchment. B. We compared the adopted reference period, which is a source of precipitation change for the climate scenarios. C. We have put together various types of ensembles - consisting of wet and dry models [6]. We present the research results in individual sheets of the included Excel file. The file contains four sheets: 1.Location: We present a graphic of the location of the calculation point for which the research was carried out. It contains a map of Poland and the Carpathian Mountains with the studied catchment marked (red). The next drawing highlights the analyzed catchment area of the upper Raba River flowing into the dammed reservoir (Dobczyce). The graphics also include data source setup for which point and areal approach scenarios were performed. The third figure on the graphic is the results of modeling average monthly sediment load for base scenario against the average precipitation monthly sums. 2. Climate change predictions: First, the reader should pay attention to the graphics. They present all implemented scenarios (outer circle with corresponding colors) and the way they are named (inside the circle). It also includes which scenarios belong to the point (P) and areal (A) approaches, and what was the reference period (10 or 30 years). The table in this sheet presents the changes of precipitation introduced in the model using the delta change tool in the model SWAT. 3. Scenarios Database - Av.: The spreadsheet presents the modeling results as average monthly sediment loads for each scenario. The data are presented in a table and a chart enabling quick comparison of annual cycle trends and their changes in various scenarios. 4. Scenarios Database - Y: The last sheet presents the full monthly sediment load data sets for all scenarios. The reader's attention is focused on the interactive pivot chart. The user should select the scenarios of interest, years or months. It is then possible to thoroughly analyze changes in the modeling results of individual monthly values and time shifts resulting from the introduction of various types of ensemble climate models. In the background there are values that can be used by the reader for their own comparative analyses, provided that the source of the data is properly cited.

Steps to reproduce

[1] Soil and Water Assessment Tool (version 2012.10_2.19) [2] Arnold JG, Moriasi DN, Gassman PW, Abbaspour KC, White MJ, Srinivasan R, Santhi C, Harmel RD, van Griensven A, Van Liew MW, Kannan N & Jha MK (2012). SWAT: Model use, calibration, and validation. Transactions of the ASABE 55(4): 1491-1508. https://swat.tamu.edu/media/99051/azdezasp.pdf [3] Szalińska, E., Orlińska-Woźniak, P. & Wilk, P. Sediment load variability in response to climate and land use changes in a Carpathian catchment (Raba River, Poland). J. Soil. Sediment. 20, 2641-2652 (2020). [4] To provide future climate information CORDEX regional climate model data for European domain with 0.11° x 0.11° horizontal resolution (https://cds.climate.copernicus.eu) were used. Future projections were calculated for two time horizons: short-term (2026-2035) and long-term (2046-2055) and for two greenhouse gas concentration trajectories (Representative Concentration Pathways): RCP 4.5 and RCP 8.5. [5] Climate change projections used in the study were adopted and implemented to further modeling as relative changes with a reference to historical climate conditions. Precipitation and temperature data were obtained from two historical meteorological data sources: i) station data from Kraków-Balice synoptic station [WMO 12566, 19°47'42''E, 50°04'40''N], ii) e-obs gridded data on a spatial resolution of 0.1° regular grid [v26e, https://surfobs.climate.copernicus.eu/dataaccess/access_eobs.php] what enabled further comparison of sediment loads estimated based on the point and areal approach. [6] To distinguish dry and wet sub-ensembles the ratio between future and reference areal monthly mean values was taken into account according to equation: RR=100(Model-future / Model-reference -1). Using the probabilistic method, anomaly dry (RR<25th percentile, i.e. 1.1 mm) and wet (RR>75th percentile, i.e. 39.2 mm) months were indicated for each model followed by the annual mean value of the calculated deviations.

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