The NRCS Handbook 590 shows about 7 acres of watershed for each acre-ft of water to be impounded (for your estimated location).

However, after the pond initially fills, then evaporation should be the main variable, so "surface acres" should be the controlling factor.

In that case, 48 acres of watershed should support a 6.9 acre pond.

However, I have posted these numbers before in the forum and people with local knowledge usually say the estimate from the Handbook is too optimistic.

Further, you should also de-rate your watershed a little, since the upstream pond will preferentially capture run off - especially during drought conditions when it is very low and you need water the most.

There are other factors beside just the area of the watershed that determine how much surface water will make it to your pond.

Steeper slopes and rocky terrain will contribute more water. Flat, lush grasslands will intercept more of the rain.

Here is a link to the handbook, which should give you lots of good information while you are in the planning stages.

NRCS Pond Handbook 590

Another option might be to add a small forage pond upstream of your 2-acre pond. If the slope allows, you could gravity drain it into your main pond during a drought. If not, then you could pump this additional water storage as needed. Further, a forage or grow-out pond might have good value to you during normal years.

Good luck on your new pond project!