The impact of intensive groundwater abstraction on recharge to a shallow regional aquifer system: evidence from Bangladesh

Quantitative evaluations of the impact of groundwater abstraction on recharge are rare. Over a period (1975–2007) during which groundwater abstraction increased dramatically in the Bengal Basin, changes in net groundwater recharge in Bangladesh are assessed using the water-table fluctuation method. Mean annual groundwater recharge is shown to be higher (300–600 mm) in northwestern and southwestern areas of Bangladesh than in southeastern and northeastern regions (<100 mm) where rainfall and potential recharge are greater. Net recharge in many parts of Bangladesh has increased substantially (5–15 mm/year between 1985 and 2007) in response to increased groundwater abstraction for irrigation and urban water supplies. In contrast, net recharge has slightly decreased (−0.5 to −1 mm/year) in areas where groundwater-fed irrigation is low (<30% of total irrigation) and where abstraction has either decreased or remained unchanged over the period of 1985–2007. The spatio-temporal dynamics of recharge in Bangladesh illustrate the fundamental flaw in definitions of “safe yield” based on recharge estimated under static (non-pumping) conditions and reveal the areas where (1) further groundwater abstraction may increase actual recharge to the shallow aquifer, and (2) current groundwater abstraction for irrigation and urban water supplies is unsustainable.