I need to figure out the best way to improve drainage of spring water flowing through my property. The water from my neighbour’s spring flows 10m through a pipe into a manhole on my side. The water level in this manhole is always 10-20 cm higher than the in and out pipes. The water then flows 30m to a second manhole on my side and then through a 10m pipe into the lake. When I replaced this last 10m pipe, I set it lower so that the water from the 30m pipe dropped 20 cm instead of 5 cm. This appeared to increase the flow considerably, but I’m not satisfied because the water level in the first manhole is still too high, even though the water falling out of the 30m pipe is only a third of its diameter. My questions: 1) When water drops out of a pipe, is the flow rate affected by how big the drop is? 2) If the pipe has an increasing gradient, does the faster water increase the speed of the following water by pulling on it or by reducing the flow resistance? 3) How does the flow work, do the water molecules stick together or are they independent like marbles and lose energy by jostling each other? 4) If I increase the diameter of the pipe only in the later half of its length, will this increase the flow? 5) If I replace the concrete pipe with a lower friction pvc pipe only in the later half of its length, will that increase the flow? As you see, I am looking for a way to improve the situation without replacing the whole 30m of pipe.