I'm planning to construct a home sometime in the near future in hot, arid part of the country. Obviously, keeping the home cool is a major concern and I've been considering all available options.

One of the recurrent ideas discussed online is using geothermal cooling. But I think I don't have enough land to implement it. I have a related idea though.

Water supplied during set hours of the day by the municipality is fairly cool even during the summer months and it is a common practice around here to first let it collect in an underground tank and then pump it to the overhead tank as needed.

What if I create a closed loop system of circulating water with two car radiators: one in the underground tank, submerged in cool water and another in the living area of the home with a fan blowing behind it.

Do you think it'll cause perceptible change in room temperature if there is, say, a temperature difference of 10 degrees Celsius between water and ambiance? I intend it to only reduce the load on the air conditioners and/or just delay the use of AC.

What kind of math/physics will be needed to assess if this is a feasibility? I tried looking hard but could not find anyone else discussing this idea, so I'm reaching out to you guys.

Thank you for your time.