I had this idea of an osmotic pump way back in high school and I never got a satisfactory answer if it would work. If I had this configuration:
Would it continually pump water up given ambient heat so long as the bottom reservoir is full?
EDIT To explain what is happening, there is pure water in each of the dark blue reservoirs, saline in the cyan containers (same concentration of saline in each container) and a semipermeable membrane at the bottom and near the top of each container.
The pure water in each reservoir would be sucked up into each container directly above it due to osmotic pressure (high water concentration flows to lower water concentration), and then dumped out at the top also due to osmotic pressure (saline to air which is almost 0% water concentration). Since the membrane is not permeable to salt, only the water is released from the container into the next higher reservoir.
NOTE that the membrane at the top of each saline container doesn't touch the pure water in the reservoir it empties into. I'm also thinking that the saline containers may have to be completely filled with extra osmotic pressure to spare to counteract the pure water that sticks to the outside of the upper membrane and cause a reverse osmosis effect. Other possible tricks relying on surface tension and gravity might also aid in pulling the water away from the membrane. END EDIT
If enough were stacked, would this allow for transporting water higher than the maximum that trees can transport (about 138m according to this article)?