25 CFR §171.525

1. (a)You can pay your bill by:
   1. (1)Personally going to the local office of the irrigation facility authorized to receive your payment during normal business hours;
   2. (2)Depositing your payment in an authorized drop box, if available, at the local office of the irrigation facility; or
   3. (3)Mailing your payment to the address indicated on your bill.
2. (b)Your payment must be in the form of:
   1. (1)Check or money order in the mail or authorized drop box; or
   2. (2)Cash, check, or money order if you pay in person.