I don't like current event. I don't think it's good. I actually think it's quite terrible, because it's basically blocking pre 20 level players from playing (no option to buy water, hard to get water in raid) and it has little to no impact on past 20 level players (additional 30k spent every raid is not really that much).
But my biggest problem is that… They put no effort into it at all. This event could be truly nice after just few tweaks.
Add some quest that would allow pre 20 level players to get few bottles of water. This would give them so needed water supply for raids, even if they don't find water in raid then they still have some water from quest and can keep on playing. This quest could come from Jaeger and be something like "Heat wave hit us hard, water supplies are running dry. I heard there may be still some water reservers in one of the old bunkers on woods. Go and scout them out". And you need to visit each bunker on map, shit maybe even leave marker there. As a reward for finding some water you get few bottles. Simple as that.
Make water depletion severity based on map. This would push players go play more on certain maps. For example, anyone who lives in city knows that heat waves are more severe there because there's little vegetation, low amount of shadow, all buildings and roads get hot and then radiate heat. At the same time outside of city it's much more bearable because lots of shadow and vegetation. So why not make it that Customs, Interchange, Factory and Reserve are causing higher depletion while Shoreline, Woods and Labs (cause they are underground) lower? That would push players to play more on these maps, for some that could be quite big playstyle change if they don't usually play these maps.
Make that time of day also impacts water depletion speed. At night it should be lower. So basically playing nighttime shoreline or woods would be close to pre event water depletion rate.
Change scav spawns so there will be more often in building or close to buildings. It would make sense they they would hide from heat and stay in shadow inside buildings instead of sitting in full heat in the middle of road.
Is this more effort for devs? Yes. But would they push some players to change their playstyle (playing maps or day times they usually don't). Most likely yes. Would it give new players some way to keep playing game? Yes.