You could switch to LRFD that has a different "weight" on dead load, 0.9D, but it creates more issues elsewhere.
If you go the other way (as some WTP and WWTP plants could go), an appropriately done PRV and making sure the flowrate can actually happen would potentially alleviate the (buoyant) uplift from water pressure, but if that's a basement, it will be filled with untreated "ground" water. I wouldn't typically consider water as a "earth pressure" load (H), it's a F load (fluid).
If the earth is saturated, the load changes but it could be parsed between the load from the soil and the 62.4 pcf from the water. There is also the more pragmatic question of just how permeable the soil is, so even if there is water above the surface, the soil itself may not be saturated, particularly if the water event is short duration and the water isn't able to percolate downward before it dissipates. That would be an adventurous load case, however. I'm not convinced anybody has gone that far into the details on your average WTP/WWTP, (segregating H and F pressures during a design flood) all the old ones are upstream/downstream of various large cities in a flood plain (1960s style eminent domain, seize the swamp, clay soils, terrible MSR values, etc.).
ETA - maybe I should back up a moment. The definition of H includes "ground water pressure," and pressures of bulk materials (grain? soils/aggregate bins?) and F is for "well defined pressures with maximum heights" so perhaps more of a chemical tank approach. If it's not a WTP or WWTP you're in a "better" situation than the typical WTP or WWTP, on the presumption it's a concrete WTP/WWTP as those have separate load factors in addition to the standard ones (ACI 350).
