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Riparian Vegetation In mountainous areas of the Southwest, streams and water courses have a wide variety of vegetation types which depend on amount of flowing water, elevation, and amount and character of alluvial deposits. Perennial Streams At the higher elevations, perennial streams have a characteristic vegetation of alders, cottonwoods, willow, aspen, and other, usually deciduous, hardwood species. These trees use a large amount of water because they grow close to the streams and may even take water directly from the flowing stream. However, in many cases, these streams should be reserved for recreation, either for undisturbed fishing streams or for potential campsites and other recreational uses. Only in a compar- atively few cases can the vegetation along these streams be cut to produce more water. There is also a question whether cutting vegeta- tion along these living streams will save water. Removing shade will increase the ~ater temperature, which will create greater evaporation losses that may not be compensated in full by reduced transpiration from lessened number of trees. It may be possible to develop methods of thinning the vegetation or removing some of the trees with the highest water use and still preserve recreational values. Intermittent Streams There are many streams in the mountain areas that do not flow continu- ously. Many are dominated by cottonwood. Clearing of the cottonwood in Arizona has reduced water loss (Bowie and Kam, 1965), but it is probable that saving some trees to shade the stream during the peak of the day would keep the water temperature lower and might even further reduce water loss. Many intermittent streams that apparently dry up completely during the dry period may still give up considerable ground water to trees. In Arizona, one of the most common trees in this situation is the Arizona sycamore. But cottonwoods, evergreen oak, Arizona ash and many others will thrive in these situations. Many of these sites have potential for recreational development, even though there is no fishing. Management plans for these areaS should prescribe certain sites to be preserved for recreation and others to be managed for water savings, depending on the particular locality. At present, the amount of water saved by clearing the natural stream may not be very high, but if the area is in a brush country where the chaparral can be converted to grass, the amount of water flowing in the streams could be increased. Then proper management of the ripar- ian vegetation to reduce evapotranspiration losses would become more critical. 4