Lake Superior, the largest of the Great Lakes of North America, is also the world's largest freshwater lake by surface area (~ 82,100 km2), and the third largest freshwater lake by volume (~ 12,100 km3). The monthly average precipitation in 2018 in the lake area was 2.69 inches. According to the data provided by USGS water stations, the total flow rate in all the incoming streams was found to be 356,747 ft3/s (cubic feet per second). At the same time, the lake discharges 717,258 ft3/s to its surrounding water bodies. The monthly average evaporation was 18.7 mm. The groundwater inflow was 783.33 km3 less than the groundwater outflow in this year. (Hints: (1) The average monthly data can be used to calculate the annual data; (2) Volume = Area * Height; (3) Pay special attention to the units, convert all the units to be consistent first.)
(1) With the information above, please write the water budget for Lake Superior (10 points);
(2) Please estimate the change of storage (in m3) in the year of 2018 (20 points);
(3) Please estimate the increase or decrease of water level (in mm) in the year of 2018 (10 points).