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Lab 9 Course Notes(1) (1)

Lab 9 Course Notes(1) (1) - GEOG 265 The Water Planet...

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Laboratory 9: Runoff Measurement and Analysis 1. LEARNING OBJECTIVES Learn the processes and factors that influence runoff. Explore the relationships between precipitation and stream response. 2. BACKGROUND INFORMATION Rivers, lakes, reservoirs, and dams provide more than 75% of the water used in the U.S. Surface water systems are also used for recreational purposes and in many cases are important transportation conduits. The importance of surface water in the development of the U.S. is illustrated by looking at a map of the nation. Virtually all cities with populations exceeding 150,000 are located on rivers, and many smaller communities are located on rivers and lakes. There are about 2 million streams and rivers in the U.S., including the mighty Mississippi River, which is the fourth longest river in the world at 3,710 miles long. Of the world’s 11 freshwater lakes with the largest surface area, 4 are located in the Great Lakes system (Superior is 1 st , Huron is 5 th , Michigan is 6 th , and Erie is 11 th ). In addition to the Great Lakes, we have many thousands of smaller lakes, dams, reservoirs, and ponds. These include 25 lakes with surface areas greater than 100mi 2 and more than 200 with surface areas larger than 10 mi 2 . All of these water bodies depend on the phenomena of runoff. Runoff is all water transported out of the watershed by streams. Some of this water may have had its origins as overland flow, while much may have originally infiltrated and traveled through the soil mantle to streams as throughflow. In addition, water that infiltrates and goes down into groundwater may later emerge far downstream through seeps and springs to add to streamflow. At that point, it also becomes runoff. While runoff is usually benevolent, under extreme conditions of rainfall or land use it can cause extensive damage by eroding soils and stream banks; carrying off valuable agricultural nutrients and pollutants; destroying bridges, utilities, and urban developments; and causing flooding and sediment deposits in recreational, industrial, and residential areas along stream systems. The hydrologic effects of deforestation, agriculture, and surface mining have been manifested since European settlement. Since World War II, we have seen a dynamic reshaping of our landscape by rapid urbanization and more intensive agriculture. These activities have changed hydrologic responses, soil erosion, and sedimentation in watersheds. For example, urbanization of farmland and forests causes more rapid runoff, higher peak discharges, and larger runoff volumes. 2.1 Runoff characteristics
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Lab 9 Course Notes(1) (1) - GEOG 265 The Water Planet...

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