Preparing soil data in the SWAT model using geological maps and remote sensing techniques (Case study: Sahajar Tonekabon watershed)
Volume 5, Issue 3, Autumn 2024, Pages 289-302
Mousa Abedini, Behnaz Saraei, Ali Talebi
Abstract Background and objective: Global soil maps, such as the data provided by FAO and other data sets, serve as an important basis for modeling hydrological processes. However, these maps are often not suitable for accurate calibration of models such as SWAT (Soil and Water Assessment Model) due to their large scale or lack of sufficient detail. This challenge is especially evident in marginal logic with limited access to data.
Research method: The present study aims to prepare a soil map and its parameters for the hydrological SWAT model of the Sehazhar watershed in northern Iran, Tonekabon County, Mazandaran Province. Therefore, using remote sensing and geological map data and slope map, it takes a step towards helping to solve this problem that exists in watershed studies in areas lacking soil data. For this purpose, first, from the World Soil Map (FAO), then by averaging based on geological map information such as formation type, period, rock type and hydrological group, and slope map, 5 general soil types with their characteristics were extracted. Then, they were converted into soil maps in Geographic Information System (GIS) software. The adjacent basin of the Sardabrood region (Kalardasht) was also used for comparison and validation.
Findings and conclusions: In this study, 10 soil factors required for use in the SWAT model were extracted, including: number of layers, soil depth, horizon thickness, bulk density, available water capacity, saturated electrical conductivity, soil organic matter, clay, silt, sand, rock in the horizon, and albedo ratio. According to the results of the study, 5 general soil types of the basin include: chernozem or pseudo-chernozem soils, verticillium, molly-soil, podzol, and lithosol. The results of the validation of the present study showed that using the above method to facilitate the preparation of soil maps and the estimation of soil data values has acceptable accuracy. Therefore, in areas without soil data and in studies with time constraints, the soil data preparation method is the appropriate method. Therefore, a promising solution is to use geological maps and remote sensing analyses to extract soil characteristics.