I am designing a riser pipe for use in ocean down to depths of 5km. Polymetallic nodules are pumped from the seabed to the surface. For my FEA and CFD analyses I need to input a maximum pressure inside the pipe but as the depth decreases, so does pressure. How do I go about calculating approximately the maximum internal pressure? I have calculated friction factor, head loss, reynolds number. Fluid velocity is 1m/s and density of the fluid is 1611kg/cm3. A pump will be used to transport this fluid upwards.