Groundwater Discharge to Upper Colorado River Basin Varies in Response to Drought (2 of 3) (image) US Geological Survey Share Print E-Mail Caption USGS scientist collects noble gas sample from spring site near Roaring Judy, Colorado. Groundwater discharge that flows into the Upper Colorado River Basin varies in response to drought, which is likely due to aquifer systems that contain relatively young groundwater, according to a new US Geological Survey study. Credit USGS Usage Restrictions Credit: USGS Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.