A research sensor lowered into an estuary records absolute pressure \(P\) as a function of depth \(h\) below the surface. As shown in the graph, the pressure increases linearly from \(100 \text{ kPa}\) at the surface (\(h = 0 \text{ m}\)) to \(310 \text{ kPa}\) at a depth of \(20 \text{ m}\). What is the density of the water in this region of the estuary?