can i use half vegetable broth and half water

depending on the recipe, you probably can do that, but can you let us know what the recipe is?

The short answer: Yes.

Depends on what you're making. I like to keep powdered broth in the pantry for cases just like this where I run short on broth. 1 teaspoon to 1 cup of water and it works great.

Depends on what you're making. I like to keep powdered broth in the pantry for cases just like this where I run short on broth. 1 teaspoon to 1 cup of water and it works great.

What are you cooking? I may be giving you a omg-this-is-way-more-comlpicated-than-it-should-be answer but here goes: Some recipes may not miss the broth and some/all water would work just fine. When I've been in this pinch before, I've made a cheaters broth by heating some olive oil in a pot over medium heat, adding some veggie scraps (celery ends, carrot peels, onion ends, garlic, herb stems) until richly browned, and then adding broth and water to bring to a simmer for an hour or so. If you don't have veggie scraps, see what's in your spice cabinet--wrap (and tie the top tightly) a combination of aromatic powders (garlic, onion) and dried herbs in cheese cloth or a muslin bag and steep in boiling water like a tea.