Hello Danielle,
I am sorry for what can be a challenge in many areas. However, land ownership does not mean "water ownership" in most countries, and "water diversion or impoundment" has been heavily regulated for almost 4000 years in several cultures.
Water is such a vital resource, as you probably know and understand, that anything that affects its flow can have huge impacts to other biomes within a given areas "water cycle."
Be positive, be cooperative, and have clear plans for what you want to achieve and most of these agencies will really bring great help to you. Many of the folks that work for the geological and hydrological surveys of most states are wonderful folks to work with...
Good luck!