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Interaction of Ground Water and Surface Water in Different Landscapes Ground water is present in virtually all landscapes, The interaction of ground water with surface water depends on the physiographic and climatic setting of the landscape, For example, a stream in a wet climate might receive ground- water inflow, but a stream in an identical physio- graphic setting in an arid climate might lose water to ground water, To provide a broad and unified MOUNTAINOUS TERRAIN The hydrology of mountainous terrain (area M of the conceptual landscape, Figure 2) is characterized by highly variable precipitation and water movement over and through steep land slopes, On mountain slopes, macropores created by burrowing organisms and by decay of plant roots have the capacity to transmit subsurface flow perspective of the interaction of ground water and surface water in different landscapes, a conceptual landscape (Figure 2) is used as a reference, Some common features of the interaction for various parts of the conceptual landscape are described below, The five general types of terrain discussed are mountainous, riverine, coastal, glacial and dune, and karst. downslope quickly, In addition, some rock types underlying soils may be highly weathered or fractured and may transmit significant additional amounts of flow through the subsurface, In some settings this rapid flow of water results in hillside springs, A general concept of water flow in moun- tainous terrain includes several pathways by which precipitation moves through the hillside to a stream (Figure 20), Between storm and snowmelt periods, streamflow is sustained by discharge from the ground-water system (Figure 20A), During intense storms, most water reaches streams very rapidly by partially saturating and flowing through the highly conductive soils, On the lower parts of hillslopes, the water table sometimes rises to the land surface during storms, resulting in overland flow (Figure 20B), When this occurs, precipitation on the saturated area adds to the quantity of overland flow, When storms or snowmelt persist in mountainous areas, near-stream saturated areas can expand outward from streams to include areas higher on the hillslope, In some settings, especially in arid regions, overland flow can be generated when the rate of rainfall exceeds the infiltration capacity of the soil (Figure 20C). Near the base of some mountainsides, the water table intersects the steep valley wall some distance up from the base of the slope (Figure 21, left side of valley), This results in perennial discharge of ground water and, in many cases, 33