A study of the effect of rainfall variability on Darakeh river flow rate during 1989-2012

Rainfall and flow rate are of the most important climatic and hydrologic parameters whose investigation and determination of their behavior are of great importance in water resources management. One of the most suitable methods available for assessment of hydro-climatological conditions in the watershed is trend analysis which is used to examine the changes of a variable during time. Current study has been implemented in two parts. The first part of the study investigates the effect of rainfall changes on Darakeh river flow rate between 1989- 2012. To do this, monthly recorded data of rainfall from Haft Howz station (on Darakeh river) and methods such as graphical Mann-Kendall and linear regression tests were used. In addition, rainfall and river discharge anomalies were examined during the 24-year period. The results indicates that rainfall time series in Darakeh watershed has a positive and rising trend, though this trend is not significant. Also river flow rate increases with a slight slope during the studied time period and doesn’t show a significant trend. Totally it can be concluded that except for some particular time periods, increase and decrease in the amount of rainfall and river flow rate has not been concordant. The second part predicts the future rainfall in the catchment using MRI-CGCM2.3.2a under A1B emission scenario for three time horizons (2030, 2060, and 2090). The overall results are representative of reduction in rainfall in Darake river basin in the future.