Simulation of the impacts of climate change on groundwater resources in eastern England

This study investigated the impacts of climate change on the Chalk aquifer in West Norfolk. A two-layer transient groundwater flow model of the aquifer system was calibrated and validated for the period 1980-1995 and provided the historic flow record for the climate change simulations. Two future scenarios were selected from the Hadley Centre's climate change experiments using HadCM2: (1) a medium-high (MH) emissions scenario; and (2) a medium-low (ML) emissions scenario of 'greenhouse' gases. Two future periods were considered: 2020-2035 and 2050-2065. Future recharge to the aquifer was estimated by adjusting the historic record of monthly precipitation and potential evapotranspiration by factors calculated from comparing control and future HadCM2-gencrated values. Impacts of climate change were evaluated by incorporating the monthly estimated recharge inputs within the flow model. The most noticeable and consistent result of the climate change impact simulations is the decrease in recharge expected in autumn for all scenarios (decreases ranging from 17 to 35%) as a consequence of the smaller amount of summer precipitation and increased autumn potential evapotranspiration. For the 2050MH scenario, these conditions lead to a 42% increase in autumn soil moisture deficit and a 26% reduction in recharge. Hence, west Norfolk can expect longer and drier summers that are predicted to have relatively little effect on summer groundwater levels (generally a I to 2% decrease) but will result in a decrease of up to 14% in autumn river baseflow volumes.