A technical system for online measuring and monitoring of the particle content in an injection water flow, wherein the technical system comprises a data gathering means, a data communication link and a data receiving means, and wherein the data gathering means comprises an image analysis apparatus provided with the following components: - at least one water sample line provided with an inlet and an outlet for throughput of a partial flow (6") of the injection water flow; - at least one pumping means connected, in a flow-communicating manner, to the water sample line for transport of said partial flow (6"); - at least one light-transparent flow portion disposed along the water sample line; - at least one camera for recording image material of the particle content in the partial flow (6"), wherein the camera is disposed at a first side of the light-transparent flow portion; - at least one light source (30, 32) for emission of light via the light-transparent flow portion and into the camera; - at least one electronic control means structured for (a) control of the image recording of the camera; (b) reception of image material from the camera; and (c) transmission of this image material to said data receiving means; and - at least one energy supply for operation of said pumping means, light source (30, 32), camera and electronic control means; - wherein the image analysis apparatus is placed under water; - wherein said data receiving means is located at a distance from the image analysis apparatus; and - wherein the electronic control means of the image analysis apparatus is connected to the remote data receiving means, whereby image material being transmitted from the image analysis apparatus may be monitored online at a remote site (50; 68), wherein the technical system also comprises an underwater line for containing said injection water flow; - wherein at least said water sample line, pumping means, light-transparent flow portion, camera, light source (30, 32) and electronic control means of the image analysis apparatus are disposed in a water-tight housing placed under water; and - wherein the inlet and the outlet of the water sample line are connected, in a flow-communicating manner, to the underwater line at a connection site located between a shipment site (50; 64) for the injection water and an injection well. - at least one water sample line provided with an inlet and an outlet for throughput of a partial flow (6") of the injection water flow; - at least one pumping means connected, in a flow-communicating manner, to the water sample line for transport of said partial flow (6"); - at least one light-transparent flow portion disposed along the water sample line; - at least one camera for recording image material of the particle content in the partial flow (6"), wherein the camera is disposed at a first side of the light-transparent flow portion; - at least one light source (30, 32) for emission of light via the light-transparent flow portion and into the camera; - at least one electronic control means structured for (a) control of the image recording of the camera; (b) reception of image material from the camera; and (c) transmission of this image material to said data receiving means; and - at least one energy supply for operation of said pumping means, light source (30, 32), camera and electronic control means; - wherein the image analysis apparatus is placed under water; - wherein said data receiving means is located at a distance from the image analysis apparatus; and - wherein the electronic control means of the image analysis apparatus is connected to the remote data receiving means, whereby image material being transmitted from the image analysis apparatus may be monitored online at a remote site (50; 68), wherein the technical system also comprises an underwater line for containing said injection water flow; - wherein at least said water sample line, pumping means, light-transparent flow portion, camera, light source (30, 32) and electronic control means of the image analysis apparatus are disposed in a water-tight housing placed under water; and - wherein the inlet and the outlet of the water sample line are connected, in a flow-communicating manner, to the underwater line at a connection site located between a shipment site (50; 64) for the injection water and an injection well.