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Eel River

Eel River title graphic  

Eel River title image, elevation transect

Questions for this Chapter

  • How do two important rivers in the Pacific Northwest - the Eel River and the Columbia River - compare to each other?
  • Does the Eel River affect chlorophyll in the Pacific Ocean along the coast of California? 
  • Where and why is there uncertainty about the accuracy of satellite-generated chlorophyll data, and why is this uncertainty important for the Eel River in particular?

Data Frames for this Chapter

Chlorophyll Concentration (SeaWiFS)

Diffuse Attenuation Coefficient at 490nm (SeaWiFS)

Global Topography (SRTM/RAMP2)

Visualizations for this Chapter

Time Series (Giovanni)

Area Plot and Mathematical Combination (NEO)

Transect (NEO)

Correlation Plot (Giovanni)

Although the Eel River does not (normally) discharge a high volume of water into the Pacific Ocean, it has the highest average sediment yield for its drainage area in the entire continental United States.  In this chapter, we will compare the Eel River to the Columbia River, the largest river in the Pacific Northwest.  Although sediment output from rivers (which may be associated with dissolved nutrients) may be correlated with increased chlorophyll concentrations in the ocean, suspended sediments also interfere with the accuracy of the satellite data.   

 

Map and Coordinates

Eel River:

eel river map

coordinates

Columbia River:

columbia river map

coordinates

 

Time Series (Giovanni)

1. Select the area specified for the Eel River

2. Parameter: Chlorophyll (MODIS)

3. Temporal:      Begin Date = 2002, Feb

                          End Date = 2008, Feb

4. Select Visualization: Time Series

5. Generate Plot

6.Choose the custom Time Scale:

                          Min=0

                          Max=25

6-year chlorophyll time series for Eel River

1. Select the areafor the Columbia River

2. Parameter: Chlorophyll (MODIS)

3. Temporal:      Begin Date = 2002, Feb

                          End Date = 2008, Feb

4. Select Visualization: Time Series

5. Generate Plot

6.Choose the custom Time Scale:

Min=0                        

Max=25

6-year time series for columbia river

Compare the total range, the maximum values, and the minimum values for each series. 

 

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Area Plot (NEO)

Eel River:

coordinates

Columbia River:

coordinates

  1. Select Chlorophyll (MODIS).  Choose the monthly Aqua/MODIS resolution.
  2. Select the 2 time periods:June 2003 – July 2000

Jan 2003 – Feb 2003

  1. Select the area for the Eel River.
  2. Under Mode, choose Mathematic Combination.
  3. Choose subtract from the first pull-down window and enter Compute. 

NEO Mathematical Combination

eel river difference

The subtraction shows the difference between the flow in the rivers between a winter month (the rainy season) and a summer month.     The yellow measures the largest differences.  Do this again with the coordinates from the Columbia River.  By looking at the two rivers’ outputs, we can see that the Eel River has a bigger seasonal difference than the Columbia River.    One reason for this may be that the Eel River is a wild and scenic river (despite some water diversions to the Russian River), and the Columbia hosts several hydroelectric dams.   Regulated flow through the dams may reduce the Columbia’s seasonal flow.  The dams have also reduced the amount of sediments carried by the river (one estimate is that the amount of sediment has been reduced by nearly 70%).  

 

columbia river mathematical combination

 

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Transect (NEO)

Eel River = Originating in Mendocino County, California, the Eel river flows northwest, running parallel to the coast.  It reaches the ocean at the coordinates:40.641389, -124.312222.  To see its full path, visit http://geology.com/state-map/california.html

Columbia River = Beginning in British Columbia, Canada, the Columbia River flows south through the Columbia Basin.  It then swings west through the Columbia River gorge near the border with Oregon.  It reaches the ocean at the coordinates: 46.244167, -124.058056.  To see its full path through Washington, visit http://geology.com/state-map/washington.html

  1. Select Global Topography (SRTM/RAMP2) Feb 11 2000 – Feb 22 2000
  2. Select an area encompassing the Eel River and Columbia River:

coordinats

  1. Choose probe to find the coordinates of each river on the map. 
  2. Draw a transect mapping each river’s path.

Eel River:

topography near eel river

 

Columbia River:

topography near mouth of columbia river

In the northern section of the Columbia River, there are higher peaks due to the Cascade Mountain Range.  This area would produce significant sediment output, but the 19 dams along the Columbia block the sediment flow to the Pacific Ocean. 

topography of northern Columbia River

 

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Area Plot (Giovanni)

The diffuse attenuation coefficient at 490 nm (K490)  indicates how deeply light at a wavelength of 490 nm penetrates into the water, and is thus an indicator of water clarity.   Water clarity is based on the turbidity – or concentration of particles – in the water.  It can serve as an indicator for phytoplankton, because phytoplankton absorb and scatter light, and therefore block it from entering deeper into the water column.   Turbidity will also be caused by sediments, and these sediments may cause errors in the methods used to estimate chlorophyll from the satellite data.    Chlorophyll and K490 will usually be well-correlated, but in coastal waters the actual chlorophyll concentration may be much different than what is estimated from the satellite data.

We can use both chlorophyll concentration and K490 to visualize how the Eel River influences the coastal waters adjacent to its outlet to the ocean.  By averaging these data parameters over several years, the area of influence becomes apparent in each.  The K490 shows the highest concentration right out of the mouth of the Eel River where the river hits the slow-moving ocean water and drops the sediments it carries.  On the other hand, the chlorophyll concentration is farther into the ocean where the phytoplankton can take advantage of both the increased nutrients and the clear sunlit water. 

  1. Select the area specified above. 
  2. Parameter:          Chlorophyll (SeaWiFS)

    Diffuse Attenuation Coefficient at 490 nm (SeaWiFS)

  1. Temporal:            Begin Date = 1998, Jan

    End Date = 2007, Dec

  1. Select Visualization: Lat-Lon Map, Time Averaged
  2. Generate Plot

k490 - eel riverchlorophyll - eel river

 

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Correlation Plot (Giovanni)

  1. Select the area specified above. 
  2. Parameter:          Chlorophyll (SeaWiFS)

    Diffuse Attenuation Coefficient at 490 nm (SeaWiFS)

  1. Temporal:            Begin Date = 1998, Jan

End Date = 2007, Dec

  1. Select Visualization: Correlation Map
  2. Generate Plot

correlation plot

 

The correlation scale ranges from 0 -1.  1 signifies that the two variables have a 1-1 (“perfect”) correlation while 0 signifies no correlation.  In other words, the ‘murkiness of the water’ is strongly correlated with the chlorophyll concentrations estimated from satellite data almost 90 percent of the time, according to this graphic. 

This graphic demonstrates one of the pitfalls of satellite-generated chlorophyll a data.  To determine chlorophyll concentrations, the satellite measures the absorption of blue light wavelengths by the organisms (phytoplankton) producing chlorophyll.  However, sediments and organic matter can also absorb, scatter, and reflect light, which affects the light levels observed by the satellite, and these interfering factors will thus affect the accuracy of the chlorophyll estimates.  Although scientists are improving the accuracy of calculations, the chlorophyll concentrations measured by satellite do not always represent the true values of chlorophyll in the ocean, particularly in coastal waters where more sediments and organic matter are usually found. 

But that does not mean that the satellite data is useless.  First of all, chlorophyll concentrations might be accurate when used in areas off the coastline where turbidity and organic matter are less prominent.  Second, chlorophyll a data (even if it is not an accurate estimate of chlorophyll concentration in the water) can still show a trend over time.  For example, if we see a spike in the data, that may indicate that the river discharge in this region was different from other years.  The cause may or may not be related to chlorophyll, but the data can still tell us about changes in water flow and water characteristics over time.    

 

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Questions

Which river has the highest sediment output?  How does the topography influence sediment output?   What other factors affect sediment concentrations in rivers?

Looking back at the Long Island Sound chapter, we learned that excessive amounts of nitrogen can spike chlorophyll levels, which, in turn, causes hypoxia or loss of oxygen in the water.  What river would you suggest for water quality monitoring to a California official who wants to reduce hypoxia along the coast?

Where is the chlorophyll data least accurate in these examples?  How does the correlation map show this? 

Why do you think the long-term average maps of K490 and chlorophyll concentration have a different shape?   Are these shapes related?

 

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