Hi Dave, Rene, Neil,
Thank you very much for sharing your information, it is a great help.
Dave, that is a good point in regards to sediment build up if one were to enclose the sensors as I had initially described. PVC piping to enclose sensors/sensor housing is a good idea. My initial thoughts would be to have the waterproof-encased data logging equipment secured on the streambank, with PVC-enclosed sensor housing running along the streambed, secured with rebar or similar. I would think you would want the sensors perpendicular to the streambed, so the end of the PVC piping would look like an upside-down U to properly position the sensors relative to the stream.
Rene, the Seeeduino Stalker looks quite promising and simpler to set up than an Arduino Board, due to the integrated solar charging circuit. I also found the GPRSBee (GSM expansion board) which is compatible with the Seeeduino Stalker at http://www.seeedstudio.com/depot/GPRSbee-rev-6-p-2445.html.
As for the turbidity sensor, I could not find a data sheet for the one that I had initially specified, although I did find another dishwashing turbidity sensor product with an associated datasheet at http://www.mouser.com/ProductDetail/Amphenol-Advanced-Sensors/165D6042P003/?qs=sGAEpiMZZMu7wllPd7wRkV6mSy2cOhey6dvnscwJVKs%3d (you can click on the Datasheet download link on this page). There are other turbidity sensors that appear to be similar but with slightly different technical specifications here http://www.mouser.com/search/refine.aspx?Ntk=P_MarCom&Ntt=100488761. I am not immediately sure what effect these differences have or how to compare these sensors or if any of them are compatible with Stalker/Arduino boards. Any help would be greatly appreciated.
I was planning on measuring stream depth (using a depth sensor, for example http://www.amazon.com/SainSmart-HC-SR04-Ranging-Detector-Distance/dp/B004U8TOE6). My first thoughts were to take an initial depth measurement of the stream, then place the depth sensor at a fixed position above the stream, and subsequently reading stream depth using the inital depth measurement and the height of the depth sensor above the stream during that initial measurement. For example, if the stream was 36 inches deep at initial measurement, and a depth sensor was placed 48 inches above the stream at the time of the initial measurement, the initial sensor output would be 48 inches (indicating that the stream depth is 36 inches). If the next day the sensor output changed to be 44 inches, we would know that the water level of the stream rose by 4 inches. I have read that stream depth can be used to approximate stream flow, so this was my initial plan, but if a flaw is apparent in this design please feel free to point it out.