ABSTRACT
Research is systematic investigation to conrm or refute hypotheses and theories. Two of the earliest research studies in forest hydrology were an 1862 precipitationinterception study in Germany (Friedrich, 1967) and an 1867 experimental-watershed study in Czechoslovakia (Nĕmec et al., 1967). Studies on fog interception by vegetation were conducted on Table Mountain in South Africa between 1901 and 1904 (Marloth, 1907, cited by Olivier, 2002). An investigation on the water budget of young trees was conducted with small-scale lysimeters at Eberswalde, Germany in 1907 (Müller and Bolte, 2009). The rst U.S. watershed study-a joint effort by the Forest Service and the Weather Bureau-began in 1911 at Wagon Wheel Gap in Colorado. The importance of understanding forest hydrology is demonstrated by the scale of research and number of experimental watersheds dedicated to this issue. Figure 16.1 plots over 400 major experimental watersheds located at 51 different sites throughout the United States that are engaged in studying the interactions between water and forests under a variety of environmental and forest conditions. These watersheds are mainly operated by the U.S. Forest Service, universities, Tennessee River Authority, Oak Ridge National Laboratory, and lumber companies. The Agricultural Research Service (ARS) of the U.S. Department of Agriculture (USDA) also maintains a network of 140 active experimental watersheds at 17 different locations in the conterminous United States (Weltz and Bucks, 2003). These watersheds are mainly in agricultural and rangeland environments. Lists of watershed studies and history of watershed research can also be found in reports by the Forest Service (1977), Callaham (1990), Binkley (2001), Ice and Stednick (2004), and Adams et al. (2004).
