Section 9.1: Surface Water Movement

Objective SES3. Students will explore the actions of water, wind, ice, and gravity that create landforms and systems of landforms (landscapes). a. Describe how surface water and groundwater act as the major agents of physical and chemical weathering.

Main Idea: Running water is an agent of erosion, carrying sediments in streams and rivers and depositing them downstream. Vocabulary: solution: a homogeneous mixture in which the component particles cannot be distinguished.

The Water Cycle The water cycle, also referred to as the hydrologic cycle, is a never-ending, natural circulation of water through Earth’s systems.

Runoff Water flowing downslope along Earth’s surface is called runoff. A number of conditions determine whether water on Earth’s surface will infiltrate the ground or become runoff.

The Water Cycle Water molecules move continuously through the water cycle following many pathways: they evaporate from a body of water or the surface of Earth, condense into cloud droplets, fall as precipitation back to Earth’s surface, and infiltrate the ground.

Conditions for runoff Soil composition: Soil that has open surface pores allows water to infiltrate. The particle size that makes up a soil helps determine the pore space of the soil. The physical and chemical composition of soil affects its water-holding capacity.

Vegetation Vegetation can slow the rate of runoff of surface water. Raindrops are slowed when they strike the leaves of trees or blades of grass, and they trickle down slowly.

Slope Water from precipitation falling on slopes flows to areas of lower elevation. The steeper the slope, the faster the water flows.

Stream Systems Some surface water flows in thin sheets and eventually collects in small channels, which are the physical areas where streams flow. Rivers that flow into other streams are called tributaries.

Stream Systems All of the land area whose water drains into a stream system is called the system’s watershed. A divide is a high land area that separates one watershed from another.

Watersheds and divides The watershed of the Mississippi River includes many stream systems, including the Mississippi, Missouri, and Ohio Rivers. The Continental Divide marks the western boundary of the watershed.

The material that a stream carries is known as stream load. Stream load is carried in three ways. 1. Suspension is the method of transport for all particles small enough to be held up by the turbulence of a stream’s moving water

2. A stream’s bed load consists of sand, pebbles, and cobbles that the stream’s water can roll or push along the bed of the stream. 3. When water runs through or over rocks with soluble minerals, it dissolves small amounts of the minerals and carries them away in the solution.

Stream Carrying Capacity The ability of a stream to transport material, referred to as its carrying capacity, depends on both the velocity and the amount of water moving in the stream. Discharge is the measure of the volume of stream water that flows past a particular location within a given period of time

Stream Carrying Capacity Stream discharge is the product of a stream’s average width, average depth, and the velocity of the water. Copy the diagram.

Floods A flood occurs when water spills over the sides of a stream’s banks onto the adjacent land. The broad, flat area that extends out from a stream’s bank and is covered by excess water during times of flooding is known as the stream’s floodplain.

When rivers overflow their banks, the floodwater deposits sediment When rivers overflow their banks, the floodwater deposits sediment. Over time, sediment accumulates along the edges of a river, resulting in natural levees.

When the water level in a stream rises higher than its banks, the river is said to be at flood stage. The flooding of a small area is known as an upstream flood. Heavy accumulation of excess water from large regional drainage systems results in downstream floods.

Flood Monitoring and Warning Systems In areas that are prone to severe flooding, warning systems, such as those established by the National Weather Service and the U.S. Geological Survey, are the first step in implementing emergency management plans. Answer questions on notes sheet.

9.2 – Stream Development SES3. Students will explore the actions of water, wind, ice, and gravity that create landforms and systems of landforms (landscapes). a. Describe how surface water and groundwater act as the major agents of physical and chemical weathering.

Objectives Describe some of the physical features of stream development. Describe the relationship between meanders and stream flow. Explain the process of rejuvenation in the stream development.

Main Idea: Review Vocabulary: Streams erode paths through sediment and rock, forming V-shaped stream valleys. Review Vocabulary: abrasion: process of erosion in which windblown or waterborne particles, such as sand, scrape against rock surfaces or other materials and wear them away

Supply of Water Stream channels The region where water first accumulates to supply a stream is called the headwaters. Falling precipitation accumulates in small gullies at higher elevations and forms briskly moving streams.

Supply of Water Stream channel  formed when moving water carves a narrow pathway into the sediment or rock Stream banks hold the moving water within them. When small streams erode away the rock or soil at the head of a stream, it is known as headward erosion.

Supply of Water Stream channels The headward erosion of Stream A cuts into Stream B and draws away from its water into one stream, in a process called stream capture.

Formation of Stream Valleys The energy of a stream comes from the movement of water down a slope. The slope of a stream channel is called the stream gradient. The gradient of the stream depends on its base level, which is the elevation at which it enters another stream or body of water.

Formation of Stream Valleys The height of a stream above its base level determines how much downcutting energy the stream will have.

Formation of Stream Valleys Meander  A bend or curve in a stream channel caused by moving water Water moving along the outside of a meander curve experiences the greatest velocity within the meander and erodes the side of the streambed. Along the inside of a meander, the water moves more slowly and deposition is dominant.

Visualizing Erosion and Deposition in a Meander The meanders of a stream are accentuated by differences in the velocity of water in the channel.

Deposition of Sediment When streams lose velocity, they lose some of the energy needed to transport sediment, and deposition of sediment occurs. Alluvial fans Alluvial fans are fan-shaped, sloping depositional features that form when water flows down steep slopes onto flat plains. Alluvial fans are composed mostly of sand and gravel.

Deposition of Sediment Delta  The triangular deposit that forms where a stream enters a large body of water Delta deposits usually consist of layers of silt and clay particles.

Rejuvenation During rejuvenation, a stream actively resumes the process of downcutting toward its base level. This causes an increase in the stream’s velocity, and the stream’s channel once again cuts downward into the existing meanders.

9.2 Summary Water from precipitation gathers in gullies at a stream’s headwaters. Stream water flows in channels confined by the stream’s banks. Alluvial fans and deltas form when stream velocity decreases and sediment is deposited. Alluvial fans are fan-shaped and form where water flows down steep slopes onto flat plains. Deltas are often triangular and form when streams enter wide, relatively quiet bodies of water.

9.3 Lakes and Freshwater Wetlands Standard SES3. Students will explore the actions of water, wind, ice, and gravity that create landforms and systems of landforms (landscapes). a. Describe how surface water and groundwater act as the major agents of physical and chemical weathering. Objectives Explain the formation of freshwater lakes and wetlands. Describe the process of eutrophication. Recognize the effects of human activity on lake development. Peyto Lake in Banff National Park, Alberta, Canada

9.3 Lakes and Freshwater Wetlands Main Idea: As the amount of water changes and the amount of sediments increases, lakes can be transformed into wetlands and eventually into dry land. Real World Link: Have you ever felt the bottom of a lake with your feet? It was probably soft and squishy from deposits of fine sediments. Lakes and ponds receive materials that are carried by rivers from upland areas. Over time, accumulation of these sediments changes the characteristics of the lake.

Origins of Lakes Natural lakes, bodies of water surrounded by land, form in different ways in surface depressions and in low areas. Lakes can form when streams cut off meanders and leave isolated channels of water stream flow becomes blocked by sediment from landslides or other sources Glaciers gouge out the land

Lakes Undergo Change Water from precipitation, runoff, and underground sources can maintain a lake’s water supply. Most lakes are temporary water-holding areas; over hundreds of thousands of years, lakes usually fill in with sediment and become part of a new landscape.

Lakes Undergo Change Euthrophication The process by which the surrounding watershed enriches bodies of water with nutrients that stimulate excessive plant growth is called euthrophication. When euthrophication occurs, the animal and plant communities in the lake can change rapidly. Algae on the surface can multiply rapidly, causing plants on the bottom to die, decreasing the oxygen supply and the fish can die.

Lakes Undergo Change Freshwater Wetlands A wetland is any land area that is covered with water for part of the year. Wetlands include environments known as bogs, marshes, and swamps.

Lakes Undergo Change Freshwater Wetlands Bogs Receive their water from precipitation Acidic soil due to breakdown of peat moss Venus fly traps can be found in bogs

Lakes Undergo Change Freshwater Wetlands Marshes Frequently form along the mouths of streams and in areas with extensive deltas Constant supply of water and nutrients allows for the lush growth of marsh grasses Grasses, reeds, sedges, and rushes, along with abundant wildlife are common in marsh areas

Lakes Undergo Change Freshwater Wetlands Swamps Low-lying areas often located near streams Develop from marshes that have filled in sufficiently to support the growth of shrubs and trees

Lakes Undergo Change Freshwater Wetlands Wetlands and Water Quality Serve as a filtering system that traps pollutants, sediments, and pathogenic bacteria contained in water sources Provides vital habitats for migratory waterbirds and homes for an abundance of other wildlife

9.3 Summary Lakes form in a variety of ways when depressions on land fill with water. Euthrophication is a natural nutrient enrichment process that can be accelerated when nutrients from fertilizers, detergents, or sewage are added. Wetlands are low-lying areas that are periodically saturated with water and support specific plant species.

9.3 Review Questions The dominant vegetation in a marsh is trees and shrubs. a. true b. false

9.3 Review Questions The eutrophication of a lake causes plants and algae to grow more abundantly. a. true b. false

9.3 Review Questions Where does most of the water in a bog come from? a. a stream b. a lake c. groundwater d. precipitation