All models are wrong, but some are useful: Determining the low (drought) and high (flood) flow characteristics in ungauged basins

Abstract

Although instrumental observations in basins are essential for understanding basin processes, acquiring observational data from all locations is challenging. Therefore, this study aims to simulate low and high flows and compare them with observations. With this aim, 90 sub-basins were generated, and hydrological response units (HRUs) were obtained by overlaying data such as land use, slope, and soil. Hydrological processes were simulated based on water balance using meteorological data within the basin and the HRUs. The model results were used for calibration by means of the SWAT-CUP using data from station E13A031. The modeled results that were obtained for simulating basin processes are considered sufficient. The different time series characteristics (i.e., magnitude, frequency, duration, and timing) belonging to low and high flow characteristics have been estimated and compared with the observed data. Even though good coherence was present between the observed and modeled low/high flow metrics, many sources of uncertainty exist that caused over-and under-estimations regarding some metrics. Furthermore, the metrics for all sub-basins have been calculated. According to the results, the Kocanaz basin reflects high differences in the metrics for low and high flows compared to the other basins. In this context, hydrological models offer opportunities for planning and watershed management in order for understanding climate and land-use changes.