LAUSR

The impacts of extreme climates on two watersheds vulnerable to hazards of drought and flooding are examined. Using 2-m resolution topography and land use information, county level soil survey data, meteorology and hydrology data, two daily SWAT models were calibrated in years 2008 to 2010 and validated in years 2012 to 2014. Using the two calibrated models, the meteorology inputs of historical extreme wet (1996) and dry years (1964–65) was selected for daily streamflow simulation using the present land surface and evaluation of changes in the urban hydrology system. Good fit results between simulated and observed streamflow values were achieved for both watersheds, with Nash-Sutcliff coefficient and R 2 higher than 0.69 for calibration and 0.66 for validation. The wet year simulation showed that the majority of peakflow events have not increased in both rivers, but baseflow decreased in the upper Christina River in comparison to 1996 records. The dry year simulation indicated that urban development over the last 55 years has led to lower baseflow and greater streamflow variability in both watersheds. The results suggest that improvements are needed in this urban ecosystem to prepare for extreme droughts like the 1960s, and effective stormwater management practices should continue for controlling stormwater runoff. Both these improvements will build resilience in the urban environment.