Groundwater Recharge Through Winter Flooding of Rice Areas

Starting from October 2017, the hydrological balance of a 36 hectares’ rice area located in Lomellina (PV), where the practice of winter flooding has been adopted since 2004, has been under investigation. Flow meters were installed on the irrigation and drainage channels, pie-zometers were positioned inside and outside the study area, and a soil survey was performed. A conceptual hydrological model simulating the water balance at the paddy field scale was developed and calibrated. Main results show that: (a) irrigation efficiency of the pilot area during the first summer season is well in line with those found for other paddy areas in the region; (b) higher percolation rates are observed in wintertime compared to summer season; (c) despite the higher percolation, groundwater level reached in winter season is slightly lower than in summer, and the groundwater depletion after the end of the flooding period is faster compared to that observed after the summer flooding; (d) to maintain higher ground-water levels at the beginning of the cropping season, which would increase irrigation effi-ciency, winter flooding should be maintained longer over time and involve larger paddy areas.