POTENTIAL IMPACTS OF LARGE-SCALE FLOODING (SEPTEMBER, 2013) ON WATER QUALITY OF THE SOUTH PLATTE RIVER, WELD COUNTY COLORADO

There has been concern regarding potential effects of oil/gas production on water resources. This was especially true during the large-scale flooding in Colorado during, 2013. The Denver-Julesburg basin in Colorado has been an area of historic oil/gas production with little research investigating potential risks to water quality. The South Platte River, which flows through an area of intensive oil and gas production, is the focus of this quality assessment. Water samples were collected in July 2013 to assess basic water quality parameters. Following this, major flooding of the South Platte River and surrounding areas occurred during early September of 2013, with several reports of damaged oil tanks and pipelines. As a result, there was great concern raised by the public regarding potential impacts to flood waters. Samples were then collected during flooding and for several weeks afterward (floodwater recession). Chloride and bromide was analyzed to understand dilution effects and trace mixing relationships of pre-flood, flooding, and post-flooding waters. Water samples were again collected from the South Platte River in July 2014 for comparison. Oxygen and hydrogen isotopes were also measured. Preliminary results indicate that chloride levels were diluted by a factor of ~2.5 between July (pre-flooding) and September (flooding). Floodwater recession samples were diluted by a factor of ~17 relative to pre-flooding analyses and had an increasing concentration trend. These results could have important implications for assessing water quality in areas of oil/gas production that may be impacted by floodwaters.