[SOLVED] Change in earth's day length due to water displacement 1. The problem statement, all variables and given/known data About 10000km3 of water is held behind dams in reservoirs around the world. Most reservoirs are at mid-latitudes, whilst the bulk of the world's oceans are concentrated near the equator. By using conservation of angular momentum, estimate by how much the overall movement of water into reservoirs has changed the length of the day. [The earth has mean density 5.5 x10^3 kgm-3, radius R = 6400km and radius of gyration 0.58R. The density of water is 1gcm-3, and, for the purposes of this question, the density of sea water is not significantly different . 2. Relevant equations i have found that radius of gyration, k has the relation k^2 = I/m 3. The attempt at a solution i have drawn the earth and showing the reservoirs as bulges at 45 degrees from the equators just to get an idea of what is going on. I guess i need to calculate the change in moment of inertia from no reserviors to having reservoirs at these latitudes. Then seeing how this changes the radius of gyration? Any ideas?