Climate-driven trends in the streamflow records of a reference hydrologic network in Southern Spain

•Streamflows in the Guadalquivir basin decreased significantly in the last 50 years.•Yearly potential evapotranspiration has experienced a significant increase.•Changes in annual precipitation were not statistically significant.•Significant changes detected in seasonal precipitation, mainly in winter.•Streamflow change is mostly attributed to changes in intrannual rainfall distribution.