Watering trees and shrubs involves feeling the soil for moisture level and providing enough water to equal about an inch of "rain," either with a sprinkler, hand-held hose, soaker hose, or (for smaller plants) a tree-watering bag. The linked page provides more guidance, but for a tree that size, in order to moisten enough of the root system, you'd probably need to use a sprinkler (if available) or soaker hose that gets repositioned a few times so it covers enough ground. The roots of the spruce will extend well past its branch spread in every direction that it doesn't run into an obstacle like a building foundation. As a very rough guideline, when watering gardens with an oscillating sprinkler, it might require running the water for over an hour in order to supply about an inch of rain. Dribbling water out of a hose is much more localized, and as such, would require much more moving of the hose to wet enough of the root zone. How long to leave a trickling hose end on would really depend on water pressure, but you can estimate the flow rate by seeing how long it takes to fill up a one-gallon or two-gallon watering can (or any jug where you know its volume).

If it's thorough enough (where a soaking permeates the soil at least 4-6 inches deep), each watering session should last the tree about a week or two, especially now that our nights are cooling off.

Miri