Water collected in the area of coal beds has strongly positive .delta..sup.13C.sub.DIC (12.Salinity. to 22.Salinity.) that is readily distinguished from the negative .delta..sup.13C of most surface and ground water (-8.Salinity. to -11.Salinity.). Furthermore, the DIC concentrations in coproduced water samples are also high (more than 100 mg C/L) compared to the 20 to 50 mg C/L in ambient surface and ground water of the region. The distinctively high .delta..sup.13C and DIC concentrations allow the identification of surface and ground water that have incorporated CBNG-coproduced water.
 This invention was made, at least in part, with the United States governmental support awarded by the U.S. Department of Energy Grant No. DE-FC26-06NT15568-Task 4. The United States Government has certain rights in this application.