Summary In addition to the oceans, where else is water found on Earth? freshwater rivers and streams freshwater lakes and reservoirs freshwater swamps ground water (freshwater) glaciers and icecaps (freshwater)

River Systems Part 1 Drainage Basins Properties of a River Upstream-Downstream Changes Longitudinal profile of a stream The Work of Streams Features of a River System

Rivers and Streams Drainage Basins and Drainage Divides A divide separates drainage basins. A drainage basin is a land area that contributes water to a river system. Figure 5.4

Rivers and Streams In a stream flow, the factors that determine velocity are: the gradient, or slope, of the stream. the channel characteristics: shape, size, roughness the discharge, or volume of water flowing in the stream (this is generally expressed as cubic feet per second)

Figure 5.5 A. Continuous records of stage and discharge are collected by the USGS at more than 7000 gauging stations in the US. Average velocities are determined by using measurements from several spots across the stream. B. Along straight stretches, stream velocity is highest at the center of the channel. C. When a stream curves, its zone of maximum speed shifts toward the outer bank.

Upstream-downstream changes Rivers and Streams Upstream-downstream changes A stream’s profile is a cross-sectional view from head (source) to mouth. The profile is a smooth curve where the gradient decreases from the head to the mouth.

Rivers and Streams Upstream-downstream changes Factors that increase downstream changes are: velocity and discharge channel size

Rivers and Streams Upstream-downstream changes Factors that decrease downstream changes are: gradient channel roughness

Longitudinal profile of a stream Figure 5.7

Rapids are common in mountain streams where the gradient is steep and the channel is rough and irregular. Although most stream flow is turbulent, it is usually not as rough as that experienced by these white-water rafters.

Rivers and Streams The Work of Streams Streams serve as erosion vehicles. The material transported by erosion is called the stream’s load. Dissolved load Suspended load Bed load

Potholes in the bed of a small stream Potholes in the bed of a small stream. The rotational motion of swirling pebbles acts like a drill to create potholes.

The suspended load is clearly visible because it gives this flooding river a muddy appearance. During floods, both capacity and competency are increased. Therefore, the greatest erosion and sediment transport occur during these high water periods.

Rivers and Streams Load is related to a stream’s: The Work of Streams Load is related to a stream’s: competence, meaning maximum particle size. capacity, meaning maximum load. Capacity is related to discharge.

Rivers and Streams The Work of Streams The deposition of a stream is caused by a decrease in velocity. The competence is reduced and sediment begins to drop out. The stream sediments are known as alluvium, which are well-sorted deposits.

Rivers and Streams Features produced by deposition The Work of Streams Features produced by deposition Deltas are formed in oceans or lakes.

Features of a River System Rivers and Streams Features of a River System Area behind the levees may contain backswamps or yazoo tributaries. Features produced by deposition Natural levees form parallel to the stream channel.