Assessing the potential impacts of various climate change scenarios on the hydrological regime of the River Kennet at Theale, Berkshire, south-central England, UK: an application and evaluation of the new semi-distributed model, INCA

A new semi-distributed integrated nitrogen in catchments (INCA) model was used to attempt to assess the potential impacts of several recent Hadley Centre climate change scenarios on the hydrological flow regime of the entire River Kennet catchment to Theale, south-central England, UK. The climatically and hydrologically anomalous period 1985-1995 was used for baseline data in an attempt to: (1) represent any possible future climatic or hydrological variability not available from scenario use alone; and (2) attain maximum possible model calibration validity under future climates by simulating extremes of within-year hydrological variability. Substantial reductions in total annual runoff occurred, with an average reduction of 18.97%. Summer and late autumn soil moisture deficits (SMDs) increased in intensity, and were also found to persist for longer periods into autumn and (occasionally) winter. A generally enhanced hydrological regime of the River Kennet was simulated, with increased seasonality overall. A greater percentage of flow was observed to occur in spring and (occasionally) winter. Month-to-month variability of flow was discovered to be greater than annual changes. An average reduction in minimum annual flows of 46.03% occurred. Implications for catchment ecology and water resource requirements are briefly discussed. An evaluation of the new INCA model's performance as a tool for climate change impacts assessment is made.