The study looked at how using both surface water and groundwater for watering rice fields affects the water balance in a specific area in Japan. They used a model to figure out how much water goes into the ground and how much is pumped out for irrigation. The results showed that even though rice fields use a lot of groundwater, the water they put back into the ground helps recharge the aquifer. About 21% of the total recharge comes from the rice fields, especially those watered by canals. This shows that using both surface water and groundwater for irrigation is important for keeping the water system in balance.