Installing water level and water quality monitoring systems in Brhmaputra tribut

I will be teaching in India, and want to start a small monitoring program of monitoring water quality and water level in some streams of the Indian northeast, which feed into the tributari

I will be teaching in India, and want to start a small monitoring program of monitoring water quality and water level in some streams of the Indian northeast, which feed into the tributaries of Brahmaputra.

I have some experience with traditional sensors and methods of datalogging- measuring salinity, temperature, conductivity , soil moisture. The methods I have used are quite expensive and I can not even think of using them in India. Then I came across Arduino microcontrollers and the sensors that interface with it, and all that seems much more affordable than what I have used before. So I ordered the simple Arduino Uno kit and completed the projects that come with it.

Now is the next step for me to actually try something out in the field. I wan to start wiith the following parameters DO, pH, and water level. I want to install these sensors at one perennial stream location, with the depth about a meter across seasons, in Meghalaya and get some data before I can try multiple locations. I am sure that all of you may have started this the first time somewhere, and I am looking to get suggestions on how to go about it. I know it is a very broad question but at this point any inputs would be great.

thanks