A watershed is an area of land that drains into a body of water. Seasonal drivers of geographically isolated wetland hydrology in a low-gradient, Coastal Plain landscape. Watersheds and The Water Cycle: A watershed is an area of land that catches precipita on (rain, sleet, snow) that flows & drains into a body of water such as a wetland, stream, river, lake, or groundwater. Regional aquifers are important sources of water for drinking, irrigation, and industrial uses in many parts of the U.S. Intermittent streams also receive groundwater inputs, but from less expansive seasonal aquifers; consequently, rather than having streamflow present year‐round, intermittent channels have surface flow present only part of the year – typically 5 to 9 months – when the seasonal groundwater aquifer is in contact with the channel bed. It is common for the length of ephemeral channels to exceed the combined total length of intermittent and perennial channels (Hansen 2001). Consequently, throughfall contributions can be greater from sapling‐sized trees than from mature trees of the same species because the former have more flexible branches and trunks. Drawing by Robin L. Quinlivan. Please check your email for instructions on resetting your password. Watersheds are fairly simple to identify in mountainous or hilly terrain because their boundaries are defined by ridges (Figure 1). The major components of a storm hydrograph are the rising limb (or climbing limb), the hydrograph peak (or peakflow or instantaneous peakflow), the falling limb (or recession limb), and the baseflow separation line (Figure 7b). Important hydrologic concepts and methods are described in detail but primarily within the context of forested watersheds since most of the nation's fresh water originates from forest lands. Long-Term Variability in Potential Evapotranspiration, Water Availability and Drought under Climate Change Scenarios in the Awash River Basin, Ethiopia. Less moisture can be held by cooler air so clouds form and precipitation occurs during lifting. The water table (top of groundwater) at various times throughout the year is shown by the dashed blue lines with the inverted triangles. Due to prolonged periods without streamflow, ephemeral reaches either do not support aquatic life, or they support only limited types of highly specialized aquatic fauna (McDonough et al. The length and connectivity of mesopores and macropores determines the fate of gravity‐drained soil water. Wind also plays a large role in controlling interception losses and throughfall of snow. Hydrologic processes govern how water moves through terrestrial environments and becomes groundwater and surface water. Identification of flood risk zones in the region of Yogyakarta. Graphical displays of discharge volumes in streams and river systems plotted against time are known as hydrographs. Limestone geology provides the exception to this generalization. In forests, the litter layer, or the accumulation of leaves, twigs, and other vegetative debris on the soil surface provides a very effective shade barrier and it reduces the rate of air exchange between the soil and the atmosphere, so forest litter is important for restricting evaporation from the soil. A simple schematic of the hydrologic cycle. In the United States, snow‐dominated systems tend to be located in the West and at higher elevations. For example, the desert Southwest receives only a few tens of millimeters of precipitation a year, while the Appalachian region receives from 890 mm in the valleys to up to 2,040 mm in the highest mountains. Each region has 3 to 30 Subregions; 222 HUC Subregions in U.S. 2,149 Subbasins in U.S.; smallest is 181,300 hectares, Typically 16,200 to 101,200 hectares; previously referred to as HUC‐11, Typically 4,050 to 16,200 hectares; previously referred to as HUC‐14. 2000). The amount of precipitation lost to interception or that becomes throughfall or stemflow each year in forests depends upon many factors, including the type and intensity of precipitation, other weather conditions, and the species of trees present (Crockford and Richardson 2000; Muzylo et al.