Most signed agreements, including the type you are considering, are valid even if not notarized. A Notary is just an official witness to the signatures. A Notary could testify, if needed, that a person actually signed the document if that person later denies signing it. Of course, any witness can do that too. And most documents do not need a witness to be valid. What's more important is that the written document state precisely what the agreement is supposed to be: meaning it states the rights and obligations of each party. Sometimes it may be hard for a non-lawyer to draft an agreement that is not ambiguous, & which clearly states the rights and obligations. I urge you to at least contact the attorney Bar Association Legal Referral Service in your county. They can refer you to an attorney who should charge you a reduced rate for a consultation on your matter. You can then find out how much it will cost you to get an attorney to draft the agreement you need. My guess is it will not be too much. Good luck!

I agree with Mr. Teitel's answer completely. I notoraized document is simply proof that the signer signed the document on a certain date. After that date, the signer's situation might change, they might die, or they might suffer financial difficulties that arise that prevent them from fulfilling whatever statement they signed. An Agreement or contract, on the other hand, whether notoraized or not, sets forth the obligations of the signer and would provide remedies available to you if the signer did not live up to his promises.

Since the agreement concerns the obligation to provide water to the land perhaps your attorney may want to make this clear on the deed, be careful.