Grape cultivation

When I bought my current property it had two grape vines. Last summer they fruited, but died back completely during that heat wave and dropped all their fruit and leaves.

I haven't seen any sign of budding or sap flow this spring so I started to cut them down, but both are apparently still alive.

I always thought grapes didn't need to be watered. The grapes at my old property survive 100+ F temps without any water every year so I didn't think to supplement. My guess is that their roots are too shallow.

Any ideas on how I can create an in-ground reservoir for them? Should it be uphill, or down? Woodchips? Rock? Something else?

How can I save them? The soil is heavy clay with a few inches of good topsoil.

If you have rain gutters near enough you can dig a hole and fill it with stones that have gaps  to hold water and direct the water into it.  I was able to use an abandoned septic drain field  that way near my grapes.

Water does flow in that general direction. I'm just not sure how to use it. Spreader dam? Wood chips? Rock? Below grade or above? Below on the slope, or above? Etc. They were placed in exactly the wrong spot for earthworks, but that's also a possibility.

I will explain my observation more thoroughly.  I have a nearly flat clay deposit field for the south half of my 5 acres and the north half is a sand gravel hill.  So the rain fall soaks into the hill and forms a swampy pond where the sand ends and the clay loam begins. converting these to swales allows the water to slowly hydrate the clay soil beside it.   As mentioned I was able to use the buried gravel drain field to hold ad disperse the the water from the new house roof near the grapes and above the garden area.  This  does not need to be a filled trench but can be a round well filled with gravel. the water being stored below the surface does not evaporate and has more time to disperse in the clay which happens  slowly. Clay soil can hold much water but it takes constant presence to soak in otherwise it runs off the surface to a lower spot such as a swale.
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