Fig. 9: Conceptual recharge model for a shallow (<50 m deep) aquifer in the Bengal Basin from ponds and rice fields.

a In phase 1 (November–April), large amounts of groundwater are extracted for rice irrigation leading to a lowering of the water table. During the same period, the aquifers are also recharged due to the lowering of the water table and higher head of ponds and rice fields. b In phase 2 (May–August), the shallow groundwater starts to recharge rapidly in response to the incoming monsoon precipitation, and by July, the aquifer is mostly recharged. c During the early part of phase 3 (September), the aquifers are completely replenished, and most of the subsequent monsoon precipitation is rejected by the aquifer. By the end of phase 3 (October), the monsoon has finished, and the flood waters have receded, beginning a period of groundwater abstraction for irrigation. The blue and gray arrows illustrate the recharge paths. For simplicity, the exchange between river and groundwater has been excluded from this figure.