I agree with esshup about moving down slope in the central gully for a pond location. (The farther you go down slope, the more water will be available to your pond.) Just inside your SE property boundary (with a little margin) would collect the most water.

Also, a swale to the SW that diverts all of the water from the next gully over to the SW could potentially add a lot of additional surface water runoff to your pond's watershed.

Good luck on your pond project!