Significant water occurs with gas production from the Milk River/Alderson reservoir within the Atlee gas field (Suffield Area) above a north-northeast trending structural low in the Mississippian Unconformity. Water samples were collected from wells with significant water production within the hole and along the flanks of the hole so that major ion and isotope analyses could be done to determine the origin of the water. Although the Milk River Formation was the reservoir of most concern, there were a limited number of wells where only the Milk River had been perforated and gas production contained a significant water cut. Multiple samples from these wells could be from any one or all of the reservoirs open to the wellbore. Samples were therefore collected from wells with water production only from the 2WS, MH and MR in order to define a characteristic that would type the MR, MH and 2WS formation waters. Mixed samples could therefore be shown to contain these endmember waters in amounts that could be determined.