Introduction to Hydrology (Geog 3511) Fall 2002 Assignment 10: Streamflow Analysis

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1 Introduction to Hydrology (Geog 3511) Fall 22 Assignment 1: Streamflow Analysis Assigned: November 26 Due: December 5 4 possible points. SHOW ALL YOUR WORK. CITE SOURCES OF EQUATIONS USED. WRITE THE QUESTION AT THE START OF EACH ANSWER. Data 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 4m 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: Stage Rating Curve The following stage-discharge data were collected in order to define the stage-rating curve. Stage(cm) Discharge(l/s) Q1) Develop a rating curve for the recorded data. The rating curve should be of the form Q! as b where a and b are parameters that are fit using a power regression, S is stage height in centimeters, and Q is the discharge in L/s. Plot the data and the rating curve using linear axes for both the stage and discharge. What is the rating curve (using the variables Q and S)? (4 points) Taking the logarithm of each side of the equation gives us log!q"! log!a" " b log!s" Fit a linear line to the log-log data. log!q"!!1.129 " log!S" Extract the coefficients a! 1!1.129! # 1!2 Therefore the rating curve is b! Q# l s $!.789!S#cm$" This equation can also be determined by fitting a power trendline in Excel to the data.

2 Comparison of records and rating curve Rating Records Rating Curve: Power (Rating Records) y =.789x R 2 = stage [cm] Q2) Plot the rating curve on log-log coordinates and show the stage - discharge records on the same plot. How well do these data (visually) match the curve when plotted in a log-log format? (3 points) Comparison of records and rating curve y =.789x R 2 =.918 Rating Records Rating Curve: Power (Rating Records) stage [cm] The model appears to fit the data better when displayed in log-log coordinates, which minimize the appearance of the error at large stage heights. Stage-Discharge records Some stage - discharge records for the channel at Martinelli Snowpatch, Niwot Ridge, Indian Peaks are included in the attached file Q3) Plot the discharge hydrograph for July 4 to 18 inc. (use a 1 minute sampling interval) (3 points) Q4) Use the rating curve to determine the stage readings from July 4 to 18 inclusive. (use a 1-minute sampling interval) (4 points)

3 Q5) Plot the air temperature for the same time period. (3 points) Martnelli Time Series 3 air temperature [deg C] or stage level [cm] or Water level [cm] air temperature [deg C] -5 7/4/94 7/5/94 7/6/94 7/7/94 7/8/94 7/9/94 7/1/94 7/11/94 7/12/94 7/13/94 7/14/94 7/15/94 7/16/94 7/17/94 7/18/94 7/19/94 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? (4 points) On 7/4/1994 at 2:15pm, the peak discharge was estimated to be L/s. The peak flow generally occurs between 1 and 3pm. The timing of the peak discharge is illustrated in the graph below. Maximum Daily Discharge Timing 16: 15: Time of Day 14: 13: 12: 7/3/1994 7/5/1994 7/7/1994 7/9/1994 7/11/1994 7/13/1994 7/15/1994 7/17/1994 7/19/1994 Date The timing of the daily peak is related to the temperature. Increased temperatures correspond with earlier discharge peaks. (see the graph below)

4 Maximum Daily Discharge vs. Temperature 16: 15: Time of Day 14: 13: y = -.61x R 2 = : Temperature [deg C] Seasonal Discharge Hydrograph Lets make a seasonal hydrography using real data from the Martinelli catchment for You ll need to obtain this data from the Niwot Ridge LTER website: select "Data" select "Data set catalog and keyword/investigator search" select "Hydrology and Geomorphology" select "Martinelli Streamflow" save as text or ascii file (should be the default). read the metadata for information on units, etc. cut out the 1985 data in EXCEL or whatever software package you prefer. 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. (3 points)

5 1994 Martinelli Daily Discharge Volume 3 25 daily discharge volume [m3] rising limb recession limb 5 4/16/1994 5/6/1994 5/26/1994 6/15/1994 7/5/1994 7/25/1994 8/14/1994 9/3/1994 9/23/1994 Q8) On what day or days was peak discharge and what was the amount of peak discharge? (2 points) Peak discharge was on 6/1/94 and was 2759 cubic meters per day. 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 Q! Q e!ct where Q is the discharge at the start of the regression time period and c is the exponential regression coefficient. (Hint: the regression coeffiecient has units!) Plot the regression curve against the data for this time period. (4 points) By visually fitting the curve by altering the Q and c parameters, we can arrive at the regression equation of Q!!32 m 3 "e!.5 1 t d