Assessment of Streamflow Drought Based on Truncation Level (TL) Using Permanent Streamflow Data in one of the Sub-Basin of Lut Desert, Iran

Drought is known as one of the main natural hazards especially in arid and semi-arid regions where there are considerable issues in regard to water resources management. The focus of the present study is mainly on hydrological aspects of drought. For hydrological drought analysis, streamflow data is used as the key variable to identify drought events with reference to a demand specific threshold level, termed as truncation level. Thus, the objective of the present study is to (a) investigate the hydrological drought characteristics in Nesa River using streamflow data; (b) determine independent drought events, their duration, and severity using the variable truncation level approach; and (c) derive streamflow drought severity index. Based on expedience probabilities, the monthly flow duration curves for Nesa River were derived. These were utilized to estimate different dependable flows, and the values of variable truncation levels were obtained for a 75% probability level for each month. These values were used to distinguish the deficit and surplus flow periods independent drought events identified using the pooling procedure. Since 10 daily flow data were utilized, the minimum deficit flow duration was 10 days. In the following, have been identified some short duration (one or two 10-daily time step) surplus and deficit events. To decide on independent drought despite the short duration inter-event surplus has been used for a pooling procedure known as inter-event time and volume criterion (IC). Eventually, identified independent drought events and also describe their duration, severity, intensity, and DSI. Analysis of independent drought Characteristics in Nesa River indicated that are prolonged dry period in the hydrological regime of this river. In addition, based on DSI, Nesa droughts mostly are in sever category. Hence, it is suggested more realistic reload occurs in management programs of this river including storage, distribution and assign to various resources.