The completion of Elephant Butte Dam on Rio Grande in 1915 inaugurated a new regimen of flow‐characteristics for that Stream and the closing of the tunnels at Boulder Dam on February 1, 1935, will cause Colorado River to turn over a new leaf and begin a better regulated life. The changes in regimen are far reaching and of great importance to the developmental program below these structures. Two factors are mainly responsible for the changes: (a) Floods originating on the main river above these reservoirs are largely absorbed and the outflow is almost wholly under control; (b) instead of the silt‐laden water that formerly passed into these reaches there now issues from the control‐gates at the dams, rivers of bluish green clearness with hardly a vestige of silt—an absolutely novel experience in the life‐history of these streams.

The behavior of a hot, magnetized plasma brought into contact with a cold wall is studied numerically in one and two dimensions. A fully nonlinear, time-dependent magnetohydrodynamic plasma model which includes thermal conduction, resistive diffusion, radiation, and ionization is used. The model is solved numerically with an Eulerian computer code which employs implicit finite difference methods. One-dimensional calculations for cylindrical geometry examine the effect of the electrical properties of the wall on the plasma. Two-dimensional calculations for cylindrical geometry show the formation of a wall-induced instability which enhances thermal conduction losses from the plasma; the re-emergence of short wavelengths, a new feature of unstable behavior, is evident in the calculations. Two-dimensional calculations for toroidal geometry show that heat losses to a cold wall lead to double-vortex convection flow of the plasma with no evidence of the formation of smaller scale convective cells.

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