if you can store water in a tank you could use a 'hydraulic ram' pump to fill the tank as it is powered directly by the water going through it. that would leave the solar / battery for the router/ netbook/LED light.
Only problem is the ready made ram pumps I've seen are not very cheap. You can make your own, largely from standard plumbing as they're not very complicated, but the valves may take a bit of careful construction and tweaking if it is to work reliably.
Or just use ball check valves. Mount one so the flow goes through it "backward", positioned with gravity holding it open under zero flow, for the waste valve.
If I understand the ol' "Water Goat" correctly (not having made one myself):
If the cycle time is large compared to the round-trip time of sound in the drive pipe, the waste valve
closing flow rate (and to a much lesser extent the opening residual pressure) controls the on time,
while the pressure ratio controls the on-versus-off duty cycle.
As long as the waste valve closes at some point below the maximum flow rate, the pump will operate,
and with good efficiency. Lengthening the cycle by adjusting the waste valve to close at
higher flow increases the available output flow rate. But if the check valve closes at a flow
rate that gives you adequate output flow you're fine. (Adjusting a ball-check waste valve consists
of adjusting the the angle of the valve - vertical being longest cycle - or somehow making the
check ball heavier if you want it to close later than it does if it's straight-up vertical.)
With gravity replacing springs there's little to get out of adjustment.
(By the way: "Water Goat" was allegedly a classic mistranslation of "Hydraulic Ram" by an
early English-to-German engineering paper trandlation program.)