A process, comprising: introducing an aqueous polymer mixture into an oil-bearing formation; producing a fluid comprised of oil, water, and polymer from the oil-bearing formation, where the produced fluid has an oil phase and an aqueous polymer-containing phase having a total dissolved solids ("TDS") content; characterized by: contacting a source water having TDS content of greater than 15,000 ppm with an ionic filter; passing a portion of the source water through the ionic filter to form treated water having a reduced TDS content relative to the source water while excluding at least a portion of the source water from passing through the ionic filter to form a brine retentate having an increased TDS content relative to the source water; mixing a partially hydrolyzed polymer having a degree of hydrolysis of from 0.1 to 0.4, the partially hydrolyzed polymer is a partially hydrolyzed polyacrylamide, and water having a TDS content of from 200 ppm to 15,000 ppm to form an aqueous polymer mixture, wherein the amount of polymer mixed with the water is selected to be sufficient to increase the viscosity of the aqueous polymer mixture relative to the isothermal viscosity of the water and wherein at least a portion of the treated water is provided as the water for mixing with the partially hydrolyzed polymer to form the aqueous polymer mixture; mixing a brine with at least a portion of the produced fluid, wherein the brine has a TDS content at least 5000 ppm greater than the TDS content of the aqueous polymer-containing phase of the produced fluid and wherein at least a portion of the brine retentate is provided as at least a portion of the brine for mixing with the produced fluid; and separating oil from the produced fluid after mixing the brine with the produced fluid. introducing an aqueous polymer mixture into an oil-bearing formation; producing a fluid comprised of oil, water, and polymer from the oil-bearing formation, where the produced fluid has an oil phase and an aqueous polymer-containing phase having a total dissolved solids ("TDS") content; characterized by: contacting a source water having TDS content of greater than 15,000 ppm with an ionic filter; passing a portion of the source water through the ionic filter to form treated water having a reduced TDS content relative to the source water while excluding at least a portion of the source water from passing through the ionic filter to form a brine retentate having an increased TDS content relative to the source water; mixing a partially hydrolyzed polymer having a degree of hydrolysis of from 0.1 to 0.4, the partially hydrolyzed polymer is a partially hydrolyzed polyacrylamide, and water having a TDS content of from 200 ppm to 15,000 ppm to form an aqueous polymer mixture, wherein the amount of polymer mixed with the water is selected to be sufficient to increase the viscosity of the aqueous polymer mixture relative to the isothermal viscosity of the water and wherein at least a portion of the treated water is provided as the water for mixing with the partially hydrolyzed polymer to form the aqueous polymer mixture; mixing a brine with at least a portion of the produced fluid, wherein the brine has a TDS content at least 5000 ppm greater than the TDS content of the aqueous polymer-containing phase of the produced fluid and wherein at least a portion of the brine retentate is provided as at least a portion of the brine for mixing with the produced fluid; and separating oil from the produced fluid after mixing the brine with the produced fluid. contacting a source water having TDS content of greater than 15,000 ppm with an ionic filter; passing a portion of the source water through the ionic filter to form treated water having a reduced TDS content relative to the source water while excluding at least a portion of the source water from passing through the ionic filter to form a brine retentate having an increased TDS content relative to the source water; mixing a partially hydrolyzed polymer having a degree of hydrolysis of from 0.1 to 0.4, the partially hydrolyzed polymer is a partially hydrolyzed polyacrylamide, and water having a TDS content of from 200 ppm to 15,000 ppm to form an aqueous polymer mixture, wherein the amount of polymer mixed with the water is selected to be sufficient to increase the viscosity of the aqueous polymer mixture relative to the isothermal viscosity of the water and wherein at least a portion of the treated water is provided as the water for mixing with the partially hydrolyzed polymer to form the aqueous polymer mixture; mixing a brine with at least a portion of the produced fluid, wherein the brine has a TDS content at least 5000 ppm greater than the TDS content of the aqueous polymer-containing phase of the produced fluid and wherein at least a portion of the brine retentate is provided as at least a portion of the brine for mixing with the produced fluid; and separating oil from the produced fluid after mixing the brine with the produced fluid.