Just a word of advice about ...

Just a word of advice about using pressure transducers and data loggers. I have a lot of experience with these devices and they are wonderful at generating great data sets, but you need to make sure the data is useful.

Firstly, you need to know the elevation of the Top of Casing (TOC) (top of the well) so you have a reference point to measure the fluctuating water table against. Then you need to know the length of the string/wire from the TOC to the transducer pressure disc (marked on the device) which can never change while it hangs in the well - so it has to be attached firmly to the J-plug/well and may need to be weighed down (I've used stainless steel lug nuts and bolts). The wells needs to be vented to the atmosphere so the J-plug/lid needs to have a vent hole but not allow in rain water (so it doesn't run into the well and mess up your measurements). After it is deployed in the well, you must measure the Depth to Water (DTW) from the TOC manually (I recommend doing this several times) in order to calibrate the transducer measurements but not when it's taking the actual reading, otherwise you mess up the water level. The software with the transducer should come with instructions and helpful software.

Sometimes its just easier to get a person to go take a water level reading. It depends on how accessible the Site is, availability of staff, and how often you need to measure the water level. If you are looking for gross seasonal changes, then sending someone out once per week maybe enough data points. But if you are investigating tidal fluctuations or there is nearby pumping, a down hole transducer is better as you can set it to collect data every 15 min or so.

Transducer measurements drift over time, so if you plan to deploy them for years they will need to be check for the amount of drift by submerging them in a known depth of water (I use a graduated beaker/cylinder). After 5 years of use, some of our transducers had drifted by 10 cm.