Development of streamflow drought severity-and magnitude-duration-frequency curves using the threshold level method

Abstract

This study developed a comprehensive method to quantify streamflow drought sever-ity and magnitude based on a traditional frequency analysis. Two types of curve were developed: the streamflow drought severity-duration-frequency (SDF) curve and the streamflow drought magnitude-duration-frequency (MDF) curve (e.g., a rainfall 5 intensity-duration-frequency curve). Severity was represented as the total water deficit volume for the specific drought duration, and magnitude was defined as the daily aver-age water deficit. The variable threshold level method was introduced to set the target instream flow requirement, which can significantly affect the streamflow drought sever-ity and magnitude. The four threshold levels utilized were fixed, monthly, daily, and de-10 sired yield for water use. The threshold levels for the desired yield differed considerably from the other levels and represented more realistic conditions because real water de-mands were considered. The streamflow drought severities and magnitudes from the four threshold methods could be derived at any frequency and duration from the gener-ated SDF and MDF curves. These SDF and MDF curves are useful in designing water 15 resources systems for streamflow drought and water supply management.