The predicted increase in mean global temperature due to climate change is expected to affect water availability and, in turn, cause both environmental and societal impacts. To understand the potential impact of climate change on future sustainable water resources, this paper outlines a methodology to quantify the effects of climate change on potential groundwater recharge (or hydrological excess water) for three locations in the north and south of Great Britain. Using results from a stochastic weather generator, actual evapotranspiration and potential groundwater recharge time-series for the historic baseline 1961–1990 and for a future ‘high’ greenhouse gas emissions scenario for the 2020s, 2050s and 2080s time periods were simulated for Coltishall in East Anglia, Gatwick in southeast England and Paisley in west Scotland. Under the ‘high’ gas emissions scenario, results showed a decrease of 20% in potential groundwater recharge for Coltishall, 40% for Gatwick and 7% for Paisley by the end of this century. The persistence of dry periods is shown to increase for the three sites during the 2050s and 2080s. Gatwick presents the driest conditions, Coltishall the largest variability of wet and dry periods and Paisley little variability. For Paisley, the main effect of climate change is evident during the dry season (April–September), when the potential amount of hydrological excess water decreases by 88% during the 2080s. Overall, it is concluded that future climate may present a decrease in potential groundwater recharge that will increase stress on local and regional groundwater resources that are already under ecosystem and water supply pressures

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Wetlands are fragile ecosystems that provide a range of useful functions. However, such ecosystems have been experiencing persistent pressures and stresses from a range of socio-economic drivers in the last few centuries. In the 21st century, changes in global climate are expected to have impacts on hydrological and water supply regimes, which will in turn impose additional pressures on wetlands. Consequently, the need for quantitative methods to evaluate the likely impact of climate change is essential if appropriate conservation strategies and integrated water management regimes are to be developed. In this paper, a methodology is presented to evaluate the implications of potential climate change on groundwater-fed wetlands underlain by an unconfined limestone (Chalk) aquifer in eastern England, one of the most vulnerable regions to climate change in the UK. A daily weather generator, a recharge model and a groundwater model have been coupled to investigate the most extreme consequences of future climate change as described by the UKCIP02 'high' greenhouse gas emissions scenario. Simulations showed that a declining trend in wetland water levels could result in loss of species with a small tolerance to dry conditions by the end of the 21st century

<p class="emsd"><span lang="EN-GB">More than half of the world’s population currently lives in urban areas. The fastest growing megacities are occurring mainly in developing countries, where stresses on water systems already pose major challenges for governments and water utilities. Climate change is expected to further burden water resource management, putting at risk governments’ ability to guarantee secure supplies and sustainable development. In this study, the significance of assessing the implications of climate change on water resources in megacities as an important component of the adaptation process is explored. The Mexico City Metropolitan Area (MCMA), one of the largest cities in the world, is presented as a case study. The downscaled outputs of the General Circulation Model GFDLCM2a for the A1B and B1 gas emissions scenarios for the period 2046–2081 and a statistical model were used to simulate the likely impacts of climate change in water resources and domestic water demand. The results showed that an increase in temperature and changes in precipitation patterns could increase household water demand for both scenarios, between 0.8% and 6.3% in the MCMA. The future projections also estimated increases of 150% and 200% in events with rainfall intensity of more than 60 mm d^-1 and 70 mm d^-1 respectively, drawing attention to the critical impacts these changes may have on flood events. Despite the uncertainty of models projections, future climate change scenarios have proven to be a flexible guide to identify vulnerabilities of water resources and support strategic adaptation planning. In order to increase their adaptive capacity and resilience to the effects of an uncertain climate change, megacities should consider implementing an integrated water resources management approach that creates opportunities through adequate policies, new technologies, flexible frameworks and innovative actions. </span></p>