Assessing and Monitoring of Drought's Impacts on Groundwater Resources: A Case Study of Abhar Plain, Iran

In this study، the impact of drought was investigated using climatological data of the Khorramdarre weather station in Abhar plain northwestern Iran during 1985/11 to 2012/10. The wet and drought years were specified using deciles index (DI). From a hyrdogeological viewpoint، the coincidence of dry period occurrence and decreasing trends of groundwater levels is strongly confirmed by the unit hydrograph of plain between 2007 and 2009. In order to assess the probability of drought occurrence، a Markov chain model was used to determine the intensity، duration and frequency of drought during 27 year period. The balance matrix، extracted from transition probability matrix، shows that the probability of drought events will be greater than occurrence of wet years on long term. The model predicts the probability of drought occurrence is 0. 19 per year and its duration will be 2. 1 years in the next 10 years. Except for dry conditions، which are likely to be followed by further dry conditions، the probability of transition from one climatological state to other is fairly random in successive periods. Results of such studies can be useful for drought risk estimation management، drought mitigation strategies، groundwater development plans and sustainable supply of water resources.