Multivariate statistical techniques, such as cluster analysis and principal component analysis were performed on 22 wellrepresentative groundwater samples gathered from different tributaries of Wadi Ranyah, Western Provence, Saudi Arabia. The collected samples were analyzed for a total of 21 water quality descriptors (variables) including major and trace elements. From traditional Durov diagram water classification, the water quality is Calcium-Bicarbonate type. In addition, saturation indices (SI) were calculated for Anhydrite, Gypsum and Halite and the results show that the water is under-saturation state. R-mode cluster analysis resulted in two distinctive sources controlling water chemistry: groundwater-rock interaction, agriculture and anthropogenic sources. The first three principle components explained 70% of the total data variability. First factor reveals strong associations between Ca 2+ , Mg + , Na + , HCO 3-, SO 4 2-, pH , TH and conductivity and trace elements as PO 4 3and SiO 2. The second factor represents the high loading of NO 3 and Mn + as the input of soil water. The third factor reveals high loading of Chloride (Cl-) which may be due to the flushing of evaporate minerals with recent rainfall recharge. Plots of samples of F1 versus F2 show approximately one group with good separation of outlier samples, where F1 versus F3 allowed good separation of two groups.

In recent decades due to many droughts many changes have been made in the quantity and quality of the country’s water resources. this factor has caused many uncertainties in the management of the country’s water resources. The purpose of this study was to improve the understanding of the effects of drought on the quantity and quality of water resources in Lorestsn province in the years 2008 to 2018 by coherence and cross wavelet method. To achieve this goal, first to drought assessment according to precipitation data has been examined using(SPI) index and then the effect of drought on Khorram river water runoff are analyzed. In the next step, the global index of water and the impact of drought on this index in the Khorram river were evaluated. In the next step, the global index of water quality(WQI) and the impact of drought on this index in the Khorram river were evaluated. The results of coherence and cross wavelet indicated which the relative effect of precipitation with a wavelet coherence coefficient of 0.6 on changes in water runoff in the Khorram river is of degree first importance. Also, the relative impact of drought with a wavelet coherence coefficient of 0.4 changes in water quality of Khorram river has been more than other factors. Therefore, climatic factors in reducing the water runoff of Khorram river from factors other are more important. Also, the research results show human factors in changes water quality of Khorram river of degree first importance.