Many thanks for your response. I checked Ecoinvent 3.6 cut off, and I believe there is a missing link between EF method (adapted) for the output water flow, giving solely the +X impact factor for the input flow ad nothing for the output flow.
In Ecoinvent 3.6 cut off regionalised, there is the +X impact factor for the input flow, but only around -0.5X for the output flow (BG). Is there a report I can refer to to understand this? As it implies such high water scarcity burdens for everything that involves electricity production in BG. And in Ecoinvent 3.5 cut off regionalised, there were the +X and -X factors, ie water scarcity burdens were very low.