Confluence of the Sacramento & American Rivers EarthCache

Water falls to the Earth from precipitation (rain).  This water falls upon the land and gravity moves it through the soil (a process called infiltration) or it runs downhill as surface runoff.  Most of the runoff finds it way into creeks, streams, and rivers and continue the downhill flow towards the ocean, fulfilling their party in the Water-cycle.

The Hydrologic Cycle: Streamflow

Gravity is the main reason for the existence of the Earth’s rivers.  Because of gravity, water is constantly trying to seek it’s way to the center of the Earth (where gravity is it’s strongest).  But because the earth is made up of so many layers it finds itself sitting in in valleys and depressions in the landscape as oceans, lakes, and rivers.

Watershed: When looking at a river, it is important to understand the river’s watershed.  A watershed is an area of land where all precipitation and runoff come together.  Large watersheds, like the Sacramento delta, often contain many smaller watersheds.  Watersheds are important because the flow of the stream, or streamflow, and the quality of the water in rivers are affected by many things and can affect life downstream.

Streamflow is under constant change.  Rainfall can cause rivers to rise.  Even if rainfall occurs miles upstream, it can have a lasting impact downstream.  A river’s size is dependent on the size of the watershed.  Larger rivers have very large watersheds while smaller rivers have smaller ones.  Likewise, rivers react to storms differently based on their size.  This was the case in December 1861 when a very heavy rainstorm eventually flooded the Central Valley forming a Lake from Sacramento all the way to Bakersfield.  Larger rivers rise and fall slower than smaller rivers.  While it may take days for a larger river to rise and fall, a smaller river can quickly flood.  It could take days for a river to drain because it must also move all of the water that fell miles upstream.

American River:

The Lower American River watershed starts in Folsom Lake, a lake created by the man-made Folsom-Dam.  Located about 30 miles east of Sacramento, the dam is a critical component to the Central Valley Water Supply Projects.  It was authorized by Congress in 1944 as a flood control unit but was repurposed in 1949 to be a multipurpose facility to store water for irrigation, domestic, municipal, and industrial use, hydroelectric generation, recreation, water control, etc.   Folsom Lake contains approximately 10,000 surface acres of water when full and contains about 75 miles of shoreline.  It extends about 15 miles up the North Fork American River and is 10 miles from the South Fork.  7 miles downstream from Folsom Dam  is Nimbus dam.  This Dam was purposed to store and release steady flow downstream into the American River.  The Dam forms Lake Natoma near Folsom.  With all of the melted snow and rain during Northern California’s wet period, the American River is highly prone to flooding.  To combat this Levee’s have been erected along 13 miles of the riverfront down towards the Sacramento River.  

The Lower American River watershed also includes the following streams: Coon Creek, Coon Creek, Markham Ravine, Auburn Ravine, pleasant Grove Creek, Curry Creek, Dry Creek, Cordova Creek (aka Clifton’s Drain), and Arcade Creek.  The American River water is generally characterized as high-quality, low in alkalinity, and mineral rich.  Turbidity levels in the American River tend to be much higher in the winter because of the melted snow coming from the Sierra Nevada than in the summer.

Sacramento River:

The Sacramento River is the largest river and watershed in California and is the second largest (after the Colombia River) dumping it’s water into the Pacific ocean.  The Sacramento watershed contains approximately 27,000 square miles and drains the eastern slopes of the Coastal Range, Mt Shasta, the Northern portion of the Sierra Nevada, and the far southwestern slopes of the Cascade.  It carries approximately 31% of the state’s total surface water runoff.  Its Primary tributaries are the Pit, Feather, and the American Rivers.

The Sacramento River Watershed lies between both the Sierra Nevada and the Cascade Rage to the east and north and the Coast Range and Klamath in the west and south.  Rising up from the volcanic plateaus and ranges of Northern California, it’s source water is comprised of 3 rivers: The Upper Sacramento River, McCloud, and the Pit.  These three rivers join the in Lake Shasta, a 4.5 million acre reservoir made by Shasta Dam.  From Shasta, the Sacramento winds south approximately 30 miles through the hills between Red Bluff and Redding.  The Clear, Cottonwood, Cow, and Battle Creek, small tributaries in the northern valley, join the Sacramento.  Northward, in Red Bluff, some of the water in the Sacramento is diverted into canals for use as irrigation in agriculture far south in the Sacramento Valley.  As the Sacramento River continues south, it is joined by the Antelope, Mill, Deer Creek, Stony, and Big Chico Creek.  The Sacramento River flows through the city of Sacramento and receives the American River, its second largest tributary (the largest is the Feather River which connects near the city of Verona about 10 miles north of Sacramento.)  Here the river divides into the main stem and the Sacramento Deep water Ship Channel.  This channel was constructed for large cargo ships.  Eventually, both waterways rejoin in the Delta near Rio Vista.  At this point, the Sacramento River is now nearly a mile wide at it’s mouth and flows into San Francisco Bay joining the Pacific Ocean underneath the Golden Gate Bridge.

Confluence:

A river confluence is simply the meeting point for two or more river tributaries.  At the most basic level, it’s the point where two rivers meet and join the main river, or mainstream.  

Confluences are critical points where extreme changes in physical processes can occur.  These changes affect both the current or local position and anywhere downstream.  There are two key variables when studying confluences: the junction angle of the two river and the ratio of discharge between the two rivers.  Both of these have been shown to directly affect the size, shape, and flow of the river downstream. Because these areas are prone to flooding they are cause for great concern as the threaten infrastructures like bridges and buildings.  Studying a confluences channel width-to-depth ratio (how wide compared to how deep the two rivers are), have helped scientists have a better understand how to manage and design of constructed river channels.  And that will help save people and property in times of floods.

To log this cache:

In an email please answer the following questions based on your personal observations:
Do not post answers as part of your log, encrypted or otherwise, or it will be deleted!

1. Estimate the distance across the American River.  Estimate the distance across the Sacramento River upstream from the confluence.  Would you say the American River is wider than the measurement you took of upstream Sacramento?  
2. Now estimate the distance of the Sacramento river after the confluence. Does the American River appear to add more or less to the Sacramento?
3. How many people in your party?
4. Describe the flow of the rivers at 2 different points: Upstream from the confluence. Does the flow here appear to be rough or smooth? Does this change after the confluence?
5. When some rivers meet, one river introduces an excess of soil, minerals, or other deposits that makes it darker than the other river. Can you see this here?

• Optional: take picture of yourself at the confluence

• _Wikipedia
• _Sacriver.org
• _{Encyclopedia Britannica}
• _{Springer References}
• _{friendsoftheriver.org}
• _{Sacramento Area Flood Control Authority}
• _{River Confluences, Tributaries and the Fluvial Network edited by Stephen Rice}

Congrats to LewisClan77 for FTF!!!!