Incidental to the work of irrigation has been what is known as the “opening out” of springs. Small springs are apt to produce bogs from which much water is evaporated, and it has been found that by running ditches through them the water can be gathered into streams instead. The streams of water thus rescued from local dissipation are consumed in irrigation during a few months of the year, but for the remainder go to swell the rivers, and the general tendency of the work is to increase the inflow of the lake. A similar and probably greater result has been achieved by the cutting of beaver dams. In its natural condition every stream not subject to violent floods was ponded from end to end by the beaver. Its water surface was greatly expanded, and its flood plains were converted into marshes. The irrigator has destroyed the dams and drained the marshes. There are a few localities where drainage has been resorted to for the reclamation of wet hay lands, and that work has the same influence on the discharge to the lake. 2. The area affected by grazing is far greater than that affected by farming. Cattle, horses, and sheep have ranged through all the valleys and upon all the mountains. Over large areas they have destroyed the native grasses, and they have everywhere reduced them. Where once the water from rain was entangled in a mesh of vegetation and restrained from gathering into rills, there is now only an open growth of bushes that offer no obstruction. Where once the snows of autumn were spread on a non-conducting mat of hay, and wasted by evaporation until the sunshine came to melt them, they now fall upon naked earth and are melted at once by its warmth. The treading of many feet at the boggy springs compacts the spongy mold and renders it impervious. The water is no longer able to percolate, and runs away in streams. The porous beds of brooklets are in the same way tramped and puddled by the feet of cattle, and much water that formerly sank by the way is now carried forward. In all these ways the herds tend to increase the inflow of the lake, and there is perhaps no way in which they have lessened it. 3. The cutting of trees for lumber and fence material and fuel has further increased the streams. By the removal of foliage, that share of the rain and snow which was formerly caught by it and thence evaporated, is now permitted to reach the ground, and some part of it is contributed to the streams. Snow beds that were once shaded are now exposed to the sun, and their melting is so accelerated that a comparatively small proportion of their contents is wasted by the wind. Moreover, that which is melted is melted more rapidly, and a larger share of it is formed into rills.