I have not used the river for harvesting energy  but I find it very good luck inetresent

In my opinion, if an obstacle or an edge is put on the bank of the river stream, the disturbance in the line of flow of water can create a rotation on the vertical shaft turbine. The power may be very less suitable for low power appliance,

Lesser amount of power may also be developed using principle applied in water flow meter.

This requires U shape trench cut on the bed of a river. the turbine shaft is on the edges of trench, such that lower blades are facing still water of trench and upper blades are facing high speed water.

Water wheel may also be tried.

But again power obtained will be less, suitable for low power application.

it's better to use only Solar energy? because I'm doing a Wireless sensor network for monitoring river, and The first option it was Solar panels but using a turbine maybe can improve the energy harvesting.

thanks a lot. 

I just gave my imagination to trap energy from continuous water flow of river. Solar & wind are other options. Nowadays, using turbine seems to be anachronism.

Thanks a lot.