Modelling the groundwater level by water balance: A case study of a mediterranean karst aquifer of Apulia region (Italy)

Groundwater is the most easily accessible resource for irrigation so, due to recent climate change with increasing needs of water, aquifers are subject to be depleted at a high rate. This study examines the groundwater level (GL) of a well in a rural agricultural area of south Italy (Apulia region), submitted to semi-arid Mediterranean climate. A simple model of groundwater recharge (R) is proposed based on the water balance where the term of evapotranspiration and runoff has been deeply investigated. R and GL are linearly linked by the specific yield Sy for karst aquifer. Starting from the analysis of the rainfall regime of the last 39 years the proposed runoff model has been designed in order to take into account periods of successive heavy rainy days, while the water lost by crops has been modelled by the potential evaporation (PE). Three models of PE were presented; the Penman and the Hargreaves-Samani ones resulted the most suitable. This study showed that the presented model, based on the simplified water balance, can estimate the groundwater R at daily scale quite accurately.