Introduction to Hydrology (Geog 3511)

Fall 2012

Assignment 4: Streamflow Analysis

Section | Lab | Assigned | Due |

012,013 | Tuesday | Tuesday, Sep 25 |
Friday, Sep 28 |

011 | Thursday | Thursday, Sep 27 |
Monday, Oct 01 |

40 possible points.

SHOW ALL YOUR WORK.

CITE SOURCES OF EQUATIONS USED.

WRITE THE QUESTION AT THE START OF EACH ANSWER.

**This lab is based on data that was collected in the
Martinelli drainage, at Niwot Ridge. Surface water samples were
collected from a seasonal stream draining the 8-ha Martinelli catchment
about 400m from the experimental area on Niwot Ridge. The Martinelli
catchment has a poorly developed soil structure with little vegetation
and is dominated by a late-melting snowpatch [Caine, 1989].**

**To look at the area on the web, go to:**

**http://www.topozone.com/map.asp?z=13&n=4433580&e=449163&s=25**

**The following stage-discharge data were collected in order
to define the stage-rating curve.**

Stage(cm) |
12.7 |
10.0 |
9.3 |
6.8 |
2.0 |

Discharge(l/s) |
19.0 |
10.2 |
3.7 |
2.55 |
0.37 |

**Q1) Develop a rating curve for the recorded data. The
rating curve should be of the form**

**where ** ** and **
** are
parameters that are fit using an power regression, ** ** is
stage height in centimeters, and ** ** is the
discharge in L/s. Plot the data and the rating curve using linear axes
for both the stage and discharge. Report the rating curve equation.**

**Q2) Plot the rating curve on log-log coordinates and show
the stage - discharge records on the same plot. How well do these data
match the curve when plotted in a log-log format?**

**Q3) Plot the stage height vs. time for July 4 to 18 inc.
(use a 10 minute sampling interval)**

**Q4) Use the rating curve to determine the discharge from
July 4 to 18. Plot the discharge vs. time for July 4 to 18 inclusive.
(use a 10-minute sampling interval)**

**Q5) Plot the air temperature for the same time period.**

**Q6) What date recorded peak flow during this period?
Describe the variation in peak flow timing over the two weeks? How is
it related to the temperature?**

**Lets make a seasonal hydrograph using real data from the
Martinelli catchment for 1994. You'll need to obtain this data from the
Niwot Ridge LTER website:**

http://culter.colorado.edu/NWT/

select "Available Data" under Data and agree to the terms.

select Hydrology under "Metadata/data available for core topics" and search for data

select "Streamflow from Martinelli Basin, 1982-"

read the metadata for information on units, etc.

save as text or ascii file (should be the default) or copy and paste the desired date range into EXCEL.

Select the column with the text data and do "Text to Columns" under the Data tab. Choose comma delimited.

**Q7) Make a seasonal hydrograph for 1994 using these data.
Be sure to label axes and include units. Identify the rising limb and
recession limb of the hydrograph. **

**Q8) On what day or days was peak discharge and what was
the amount of peak discharge?**

**Q9) Estimate the recession coefficient as an average for
the falling flows of the record. Use the data from period 7/14-8/6. The
regression equation is of the form**

**where ** ** is
the discharge at the start of the regression time period and **
** is the
exponential regression coefficient. (*Hint: the regression coeffiecient
has units!) Plot the regression curve along with the data for this time
period.
**

**To accomplish this, there is an example
Excel spreadsheet.
The example is for 1985 data, so you will need to replace the
data (column B) with the appropriate time period. The model calculations
(which use the recession curve equations) are in column D. By modifying the
parameters Q0 and c (in cells D3 and D4), you can visually fit the model to
the data.
Cell E5 is the sum of squared error between the data on the model. The lower
you can make this value the better your model fit is.
The end result you are looking for are the values of Q0 and c that best
match the model to the data. Don't forget to adjust the formula in E5 to include the whole dataset!
*Hint: To get the best answer, try using the Solver in Excel to minimize the sum of the squared errors.**

**Q10) Provide a coherent guess as to why peak discharge has
such a large and well-defined shape? **

**Q11) Why is the early summer discharge highly variable,
compared to the discharge in late summer? **