Depending on the specifics of your installation, the parts you buy are likely to be different.
Start by considering the different things you want to measure about the stream. In its standard configuration, the device uses sensors measures stage height, water temperature and water conductivity. If you would like to measure other things about your water body, you’ll have to design a circuit to control it and modify the device code to measure from your new sensor. For example, the ultrasonic range sensor we use requires 5V to function properly, this required us to add a 5V voltage boost module to our PCB.
The standard configuration is based around a Particle Electron 3G. Switching to another Particle microcontroller will require some modification of the device code. Switching to a non-Particle Microcontroller will likely require rewriting the device code.
The battery is the largest component of the device and different situations may call for different battery chemistries. In its standard configuration, the device uses 15 AA batteries in sets of 3 in series (4.5V). This mimics the voltage of a LiPo cell meaning that the existing voltage regulation circuit on the Particle Electron can be used. This pack is designed to last about 1 year, but your milage may vary.
Alkaline batteries were chosen for their high stability at a wide range of temperature and relatively high energy density. Factors like serviceability, temperature range and size limitations may lead you to choose a different battery size or chemistry.
The onboard voltage regulator for the Particle Electron is designed to handle voltages from 3.6V to 4.4V. While a AA pack does exceed this, we have had no issues with it. See the datasheet for more.
The enclosure is the most variable part of the hardware. In its standard configuration, the device is contained within a 4x6x2.8 in. ABS water resistant box. You should only consider this option if there is little to no chance of submersion or vandalization for your device. Keep in mind that the standard enclosure is the absolute minimum in terms of size, strength, and water resistance.
The enclosure will need holes drilled, and must be easily mountable. Additionally, it cannot be metal if you plan to use an internal antenna.