I'm in the Northern hemisphere as well, and I find water cooling to be extremely advantageous year 'round!
In summer, it cools more efficiently than AC, allowing me to operate fewer watts to cool more lamps. Since it does dehuey duties as well, these savings are amplified!
In winter, the unit delivers heat without smell to my living space, saving me the cost of heating my home. In Colorado! It does this while continuing to deliver the same efficiency advantages as it does all summer.
In addition, a well designed and integrated water chilling system will use the RDWC water volume as a temporary heat sink if the heat load exceeds its cooling capacity for a short time, such as through the hot part of a summer afternoon.
How the hell does it do that?! It moves heat around the system, right? If the chiller gets behind, the chilling reservoir starts to warm up, and the water passing through the exchangers in the RDWC system(s) is warmer than usual- and thus ends up being cooled by it instead.
This is effective with temperature differences of just a few degrees- which translates into an enormous amount of heat storage when multiplied across a multi-site big tub RDWC system, let alone several of them.
When the heat load of late afternoon finally dissipates, the chiller just chugs away until it catches up with the excess heat in the RDWC water.
So how much does all this heat storage actually raise the RDWC's water temperature? Maybe two to three degrees... VERY tolerable, considering the water temp comes back down every night and I don't need to buy or operate as much cooling capacity. That's money in my pocket, courtesy of carefully engineering disparate systems together into a symbiotic whole.
None of what I'm doing is unique- doing it all here, together, in the service of more efficient and effective indoor horticulture, now, there's the new bit!