River flow will be driven by water abstraction and precipitation, and influenced by evapotranspiration. Evapotranspiration will be affected by air temperature, CO2 changes, net radiation, vapour pressure and wind speed, all of which may change with changing climate (Donohue et al. 2010). Other factors that may influence river flow include changes in catchment vegetation or other land cover, groundwater recharge and freshwater abstraction. Reduced freshwater inflow is likely to have a negative impact on water quality, particularly for intermittently closed estuaries (Nicholson et al. 2008), and may lead to development of hypersaline conditions. Nutrient and detrital input may also change with flow, which may alter ecological functioning of estuarine areas (see below).