Time series analysis of ground water table fluctuations due to temperature and rainfall change in Shiraz plain

Abstract

This research aims at forecasting ground water fluctuations due to temperature and rainfall effects using time series and cross-correlation analysis. Box Jenkins’s time series model was analyzed and the best one for Shiraz plain proved to be multiplicative seasonal. This model was used to forecast the future ground water fluctuations as affected by long term temperature and rainfall data. Results showed that the average annual water table elevation was 1499.31 for year 2021. The elevation for the year 2007 was 1501.03 showing 1.72 meter decline. Among 29 wells, statistical analysis showed that 89% of the wells had a negative correlation with monthly temperature but 86% of them showed a positive correlation with monthly rainfall. A cross-correlation analysis using individual wells showed 44.8% of wells had a delay time due to temperature changes between zero to 2 months, 51% between 10 to 14 months and only 3.5% of 26 months. Also, 72.4% of wells had a response time due to rainfall of zero to 2 months, 24.1% between 11 to 23 months and the response of 3.5% was 38 months. On average, the delay time of water table fluctuation due to temperature changes for Shiraz plain was 13 months and due to rainfall was 1 month. Key words: Box Jenkings model, temperature, rainfall, cross-correlation, water table level, plain, correlation, time delay, change, multiplicative seasonal model.