You're gonna need a bigger pot. Sure, you can do partial boils. Boil your wort and top off with water. But I personally don't like to do that. It's a PITA and some styles of beer just don't work well with partial boils. But I do understand that people must be inventive if they don't have the funds, space, or equipment to do full boils. I'm not downing anyone's technique.
And +1 on the pot size mentioned above. My rule is 2.5 - 5 gal over what you're target volume is. IMHO, find a 15gal pot if you're gonna do full boils with 10gal batches.