Domestic Water Supply Dynamics Using Stable Isotopes <i>δ</i><sup>18</sup>O, <i>δ</i>D, and d-Excess

Abstract

Surface water is the greatest contributor to many water supplies in urbanized areas. Understanding local water sources and seasonality is important in evaluating water resource management, which is essential to ensure the sustainability of water supplies to provide potable water. Here we describe the municipal water cycle of Columbus, Ohio, USA, using δ 18 O, δD, and d-excess, and follow water from precipitation through surface reservoirs to a residential tap between May 2010 and November 2011. We show that trends in water isotopic composition of Ohio precipitation have a seasonal character with more negative values during the winter months and more positive values during the summer months. The year of 2011 was the wettest year on record in Central Ohio, with many months having high d-excess values (>+15‰), suggestive of increased moisture recycling, and possibly moisture introduced from more local sources. Tap waters experienced little lag time in the managed system, having a residence time of ~2 months in the reservoirs. Tap waters and reservoir waters preserved the isotopic signal of the precipitation, but the reservoir morphology also influenced the water residence time, and hence, the isotopic relationship to the precipitation. The reservoirs supplied by the Scioto River function like a river system with a fast throughput of water. The other reservoirs display more constant solute concentrations, longer flow-through times, and more lacustrine qualities. This work provides a basic understanding of a regional water supply system in Central Ohio and helps characterize the water flow in the system. These data will provide useful baseline information for the future as urban populations grow and the climate and hydrologic cycle changes.

Variations in Dissolved Nitrate, Chloride, and Sulfate in Precipitation, Reservoir, and Tap Waters, Columbus, Ohio

“…These meteorology data were previously published in Leslie et al [13], and are noted here for context. The precipitation totals for this study were above the 25-year average monthly precipitation totals for central Ohio for more than half of the months in this study (May 2010 to November 2011; Figure 2).…”

“…More recently in 1978, the Alum Creek Reservoir was built as a supplement supply to the Hoover Reservoir. Leslie et al [13] provides the complete water supply history and describes each reservoir capacity for storage and demand.…”

“…The DRWP is designed to treat up to 2.5 × 10 5 m 3 day −1 . Leslie et al [13] reported a residence time of approximately 60 days for water movement from the reservoirs to a DRWP household tap.…”

“…The reservoirs that contribute to the Columbus, Ohio, water supply are Griggs, O’Shaughnessy, Alum Creek, and Hoover [13]. The Dublin Road Water Plant extracts water from Griggs and O’Shaughnessy for water supply usage.…”

“…With increasing suburbanization in nearby urban areas of Columbus, Ohio, the need to understand current water resource dynamics is extremely important in terms of anticipation of future meteorological and hydrological conditions. Our previous work has demonstrated that temporal meteorological variations over monthly to multiple monthly periods greatly impacted the residence time of water in the watersheds that flow into the reservoirs [13]. The purpose of this work was to evaluate the relationship between the geochemistry of local precipitation, reservoir waters derived from the drainage from agricultural lands north of the city of Columbus, and household tap water over 19 months, during much of that time with above average precipitation amounts.…”