The western state of Maharashtra in India experiences very high inter-annual variability in rainfall, particularly in districts falling in the low rainfall regions. As a result, the ground water level fluctuate widely between years. The task of interpreting the monsoon water level fluctuations becomes complex due to the wide heterogeneity in the geological and geohydrological environment of the state. However, understanding the monsoon water level fluctuations and what it means for the annual groundwater availability is extremely crucial for planning sustainable water supply schemes in the rural areas as many of the rural water supply schemes in the state are dependent on the shallow aquifers that get replenished by monsoon rains. A statistical model that explains groundwater behaviour for the state of Maharashtra is presented and discussed in this chapter. For developing and validating the model, time-series data at both district and state-level were utilized, including rainfall, pre and post monsoon groundwater levels, as well as spatial datasets on specific yield, and recharge potential were used. The model considered three variables that affect the recharge from rainfall which have not been considered in the past by groundwater researchers. They are: infiltration characteristics of the overlaying strata, the pre-monsoon depth to water levels and specific yield of the aquifer. The model shows that water level fluctuation during monsoon is a direct function of monsoon rainfall, recharge potential of the terrain and pre-monsoon depth to water level, and inversely proportional to the specific yield of the aquifer. The sensitivity of water level fluctuation during monsoon to change in pre-monson depth to water levels was also found to be varying across districts.