Okay, I don’t know if any investigator out there will find this relevant to their work, but I have a weakness for searchable databases. That doesn’t sound very exciting. The Environmental Working Group has developed interactive maps of irrigation districts, searchable by state and county, that show how much water is delivered to virtually all project farms.
The EWG reports that

Sixty percent of all farmers and ranchers do not collect government subsidy payments, according to USDA, mostly because the crops and livestock they produce do not qualify for subsidy programs (see state breakdown). Among subsidy recipients, large farms collect almost all the money. Nationwide, ten percent of the biggest (and often most profitable) subsidized crop producers collected 72 percent of all subsidies, averaging $34,424 in annual payments between 1995 and 2003. The bottom 80 percent of the recipients saw only $768 on average per year.