Regionalization of low flow characteristics of the Tigris Basin in Turkey

Low flows occur in rainless periods and changes randomly from one year to another. Water drafted from a river for various purposes depends on low flows observed in the dry periods in which flow is less than the mean level. Low-flow studies are important to take measures for reducing the negative effects of dry periods.Low-flow regime of rivers may be analyzed in various ways according to the type of the data and the desired result. In this study, the at-site low flow characteristics are estimated by baseflow, low-flow flow duration curve and low-flow flow frequency analyse methods. These low-flow characteristics are, mean flow (MF), baseflow index (BFI); 50, 90 and 95 percentiles of the time discharge exceed for 1-day flows (Q95), mean annual 7-day minima (MAM7), 7-day minimum flow estimates for the recurrence intervals of 2 and 10 years (7Q2, 7Q10).Regional dimensionless flow-duration type curves and low flow-frequency distributions (regional recurrence functions) are derived considering geographical proximity, upstream-downstream relationships, catchment alimentation, etc conditions. Besides, mean flow ? precipitation area, Q95 ? MAM7, Q95 ? TAİ, MAM7 ? TAİ regional relationships are established in order to use in ungauged and insufficient gauged sites.