An Evaluation of the Effect of Recent Droughts on Lakes Discharge Reduction: A Case Study of Lake Keeyow, Khorramabad, Iran

In the current research،the Standardized Precipitation Index (SPI) and Standardized Discharge Index (SDI) were used to analyze the temporal characteristics of droughts and its effect on discharge reduction of lake Keeyow. In this regard، first، the relation between participation and discharge was assessed and time lag of participation effect on Keeyow spring discharge was calculated. Then the standadized discharg data (SDI) was bilaterally compared with SPI series in four time intervals (3، 6، 9 and 12 months)، using coefficient of determination and pearson correlative coefficient. Then، time lag of effect of metrological drought on hydrological drought was calculated. Results showed that the temporal relation between occurrence of meteorological and hydrological droughts is significant on 99% level of confidence. This significance has a maximum in 6 months interval. Also، drought has decreased discharge of lake Keeyow. So that drought has affected on discharge of the spring in the same month (3 and 6 months time intervals)، or one month later (9 and 12 months time intervals).