An integrated system comprising: a desalination plant comprised of a reverse osmosis array to produce a RO permeate blending stream and a nanofiltration array to produce an NF permeate blending stream; a blending system; a control unit; and an injection system for an injection well that penetrates an oil-bearing layer of a reservoir, the injection system (17/18) comprising an injection line and at least one injection pump; wherein the blending system (17/18) is configured to blend the RO permeate blending stream and the NF permeate blending stream to produce a blended injection water stream and to pass the blended injection water stream to the injection system (17/18), wherein the control unit is configured to dynamically alter operation of the blending system to adjust amounts of at least one of the RO permeate blending stream and the NF permeate blending stream to alter the composition of the blended injection water stream from an initial composition to a target composition, wherein the control unit is configured to monitor the pressure in the injection well or at a wellhead of the injection well, in real time, for an increase in pressure to a value at or above a threshold value; and, if the control unit detects an increase in pressure to a value at or above the threshold value, the control unit either ceases to dynamically alter the composition of the blended injection water stream or dynamically alters the composition of the blended injection water stream, until the pressure falls to below the threshold value, or wherein the control unit is configured to monitor the flow rate of the blended injection water stream in the injection line of the injection system (17/18) downstream of the at least one injection pump, in real time, for a decrease in flow rate to at or below a threshold value; and if the control unit detects a decrease in flow rate to a value at or below the threshold value, the control unit either ceases to dynamically alter the composition of the blended injection water stream or dynamically alters the composition of the blended injection water stream, until the flow rate increases to above the threshold value. a desalination plant comprised of a reverse osmosis array to produce a RO permeate blending stream and a nanofiltration array to produce an NF permeate blending stream; a blending system; a control unit; and an injection system for an injection well that penetrates an oil-bearing layer of a reservoir, the injection system (17/18) comprising an injection line and at least one injection pump; wherein the blending system (17/18) is configured to blend the RO permeate blending stream and the NF permeate blending stream to produce a blended injection water stream and to pass the blended injection water stream to the injection system (17/18), wherein the control unit is configured to dynamically alter operation of the blending system to adjust amounts of at least one of the RO permeate blending stream and the NF permeate blending stream to alter the composition of the blended injection water stream from an initial composition to a target composition, wherein the control unit is configured to monitor the pressure in the injection well or at a wellhead of the injection well, in real time, for an increase in pressure to a value at or above a threshold value; and, if the control unit detects an increase in pressure to a value at or above the threshold value, the control unit either ceases to dynamically alter the composition of the blended injection water stream or dynamically alters the composition of the blended injection water stream, until the pressure falls to below the threshold value, or wherein the control unit is configured to monitor the flow rate of the blended injection water stream in the injection line of the injection system (17/18) downstream of the at least one injection pump, in real time, for a decrease in flow rate to at or below a threshold value; and if the control unit detects a decrease in flow rate to a value at or below the threshold value, the control unit either ceases to dynamically alter the composition of the blended injection water stream or dynamically alters the composition of the blended injection water stream, until the flow rate increases to above the threshold value.