I do not think that this formula can exist!. Think about the nature of your question? The "water needs" equal evapotranspiration + groundwater recharge (or deep seepage) + runoff. Given the fact that evapotranspiration is known in your case, you need an estimate of groundwater recharge and runoff. These two parameters depend on many different factors than just soil texture. If you are working in a specific region, where all other factors can be considered constant, you may derive some statistical relation locally, but there are cetainly no generic equations since all the other factors do vary. Hope this helps.

i completely agree with Jetse Stoorvogel.

Evapotranspiration estimation includes soil characteristics also. for further information you may verify

FAO Irrigation and Drainage Paper No. 56

Crop Evapotranspiration

(Guidelines for computing crop water requirements)

available in the following web page

https://www.kimberly.uidaho.edu/water/fao56/fao56.pdf

Thanks all of you for your inputs. I Think that FAO 56 fits better to my needs