Deuterium abundance in well water is generally similar to that in seawater, as both originate from the same hydrological cycle involving evaporation and precipitation. The typical ratio of deuterium to hydrogen in seawater is approximately 1 in 6419 or 6420 molecules. However, local variations can occur due to different environmental factors affecting water sources. The isotopes of hydrogen, including deuterium, can undergo fractionation during evaporation and precipitation, leading to slight differences in concentration. Overall, while well water is well mixed, its deuterium content may vary slightly from that of seawater.