153 RAINFALL TREND AND ITS VARIABILITY IN AURANGABAD DISTRICT, MAHARASHTRA, INDIA M.L. Dhumal 1 , S.M.Deshpande 1 , A. R. Borgawkar 2 and K.R. Aher 3* 1 Department of Mathematics, Deogiri College, Aurangabad, Maharashtra, India 2 Post Graduate Department of Geology, Institute of Science, Aurangabad, Maharashtra, India 3 Groundwater Surveys and Development Agency, Aurangabad, Maharashtra, India *E-mail- kailashgis@gmail.com Abstract Variation in rainfall has a great impact on agriculture, subsequently on economic and social life of human beings. Identification of spatial and temporal trend of hydrometrological variables is important for sustainable management and development of water resources in future. The present study is an attempt at evaluating the spatial and temporal rainfall variability in Aurangabad district, Maharashtra, India. The south-west monsoon of Indian Ocean dominates the climate and rainfall distribution in the study area and the district receives normal rainfall of 687.75 mm. The long-term annual rainfall data from 1901 to 2020 were considered. The daily rainfall during the monsoon months in the entire district was also analyzed for the last three years from 2018 to 2020. It was observed that spatial and temporal variability is high and furthermore the pre-monsoon (May) and post-monsoon (October) groundwater table fluctuation data in 141 observation wells were analyzed and interpreted to know the correlation between rainfall and groundwater levels. Keywords: Rainfall, Rainy days, Moving average rainfall, Groundwater level, Aurangabad. 1. Introduction Rainfall is one of the major regulating factors in hydrological processes, rainfall variability being linked to awide-range of hydrological phenomena such as groundwater quality and quantity, flood and drought, urban water security, agricultural crop yield, food security and hydro-power generation (Lehner et al., 2006; Murali and Afifi, 2014; Aher and Deshpande, 2014; Lockart et al., 2016; Kern and Characklis, 2017; Aher, 2017; Chowdhury, et.al.,2019; Aher et al, 2019). The south-west monsoon in the Indian subcontinent is characterized by significant rainfall that contributes about 75–90% of the total annual rainfall in India (Mooley et al. 1981), though the amount of rainfall received during the monsoon season depicts large variability in time and space. This spatial and temporal variability of the Indian summer monsoon rainfall (ISMR) increases the complexity in its prediction in the smaller space–time domain and with the aim to achieve improved prediction skill of ISMR on smaller spatial scales, a large number of studies have been done to construct contiguous regions over the Indian landmass. Average over a homogeneous region reduces the data volume and takes care of small-scale variability (Nicholson, 1986) and also, averaging helps in enhancing the signal variation on larger spatial scales (Kakade and Kulkarni, 2017). Rainfall and rainfall-related quantities have been recorded for centuries (Hurst,1957; Hurst, et al, 1965). All these measurements, however, have the disadvantage of low temporal resolution and low sensitivity. Rain measurements are based on the simple idea of collecting rain in a container and measuring the amount of water after a certain time. Time intervals between the readings are typically hours or days. Even with the most sophisticated of these conventional methods, the finer details of rainy events cannot be captured at all and very light rain might not be recorded due to evaporation or insufficient sensitivity of the instrument, making it impossible to address questions regarding single rainy events (Peters, et.al., 2001). Change in climate is a long- term phenomenon and an alarming issue for the entire world, therefore quantification of climate changes has become the preliminary step. Identification of temporal trend in hydrometrological variables will become important for sustainable management and development of water resources in the future. Rainfall is one of the most important events in the hydrological cycle (Berryman, et.al., 1988; Verma and Dhiwar, 2018). Identifying the impact of climate change on hydrological systems and water resources (greenhouse effect, increase in temperature, reduction in rainfall, etc.) is a major challenge for humanity. Climate change is considered the greatest Journal of Applied Geochemistry Vol. 23, No. 3 (2021). pp. 153-166