Abstract
The quantitative prediction of hydrological components through hydrological models could serve as a basis for developing better land and water management policies. This study provides a comprehensive step by step modelling approach for a small agricultural watershed using the SWAT model. The watershed is situated in Petzenkirchen in the western part of Lower Austria and has total area of 66 hectares. At present, 87% of the catchment area is arable land, 5% is used as pasture, 6% is forested and 2% is paved. The calibration approach involves a sequential calibration of the model starting from surface runoff, and groundwater flow, followed by crop yields and then soil moisture, and finally total streamflow and sediment yields. Calibration and validation are carried out using the r-package SWATplusR. The impact of each calibration step on sediment yields and total streamflow is evaluated. The results of this approach are compared with those of the conventional model calibration approach, where all the parameters governing various hydrological processes are calibrated simultaneously. Results showed that the model was capable of successfully predicting surface runoff, groundwater flow, soil profile water content, total streamflow and sediment yields with Nash-Sutcliffe efficiency (NSE) of greater than 0.75. Crop yields were also well simulated with a percent bias (PBIAS) ranging from −17% to 14%. Surface runoff calibration had the highest impact on streamflow output, improving NSE from 0.39 to 0.77. The step-wise calibration approach performed better for streamflow prediction than the simultaneous calibration approach. The results of this study show that the step-wise calibration approach is more accurate, and provides a better representation of different hydrological components and processes than the simultaneous calibration approach.
Highlights
Hydrological models are becoming increasingly popular and necessary in hydrological studies because they serve as important time and cost-effective tools for simulating hydrological processes [1]
This study investigated the impact of incorporating runoff, groundwater flow, crop yields and soil moisture data during Soil and Water Assessment Tool (SWAT) model calibration and validation, and compared the step-wise calibration method with the widely used simultaneous calibration method
The results of this study show that both methods can be successfully used in SWAT
Summary
Hydrological models are becoming increasingly popular and necessary in hydrological studies because they serve as important time and cost-effective tools for simulating hydrological processes [1]. Models make it possible for users to manipulate system variables and provides a safe environment for testing different scenarios and management strategies which can play a major role in prevention of water-related natural disasters [2,3,4,5]. Since it is often not possible to acquire data at the required temporal and spatial scale, hydrological models provide a quick tool for estimating stream flow, sediment yield, nutrients and other parameters, thereby complementing field experiments and observations [6]. A variety of models have been successfully utilized in hydrological and soil erosion modelling Among these models are the Water Erosion Prediction Project (WEPP) model [7], Agricultural Non-Point Source Pollution (AnnAGNPS) system [8] Areal Nonpoint Source
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