CEE 577 28 March 2006

MID-TERM EXAM

Closed book, 1 sheet of notes allowed.

I.                    (50%) Whole Hog creek flows through and area of the North Carolina Piedmont that is heavily populated with pig farms.  The creek discharges into a lake used for recreational purposes.  Concern over phosphorus loading of the lake has led to a short-term study of nitrogen imputs during storm events.  Data from this brief, 8-day survey period is shown below.

a.       Determine the total phosphorus concentration for each day using the standard log-log model

b.      Estimate the mean mass loading of phosphorus (in kg/d) into the reservoir based on these values.

 Day Flow (m3/s) Total Phosphorus Concentration (µg/L) 1 0.2 2 0.5 12 3 4.2 4 13.1 55 5 2.2 6 8.3 7 2.3 8 0.9

Porkbarrel Battery Co. Data

 Year Output (batteries/yr) 2005 5,800,000 2010 5,100,000 2015 4,400,000 2020 3,700,000 2025 3,000,000

1. Calculate the expected lead concentration at the beginning of the year 2020.
2. Determine the year when the maximum Pb concentration will drop below 0.05 µg/L.

III.       (50%) On a separate sheet of paper, answer any five (5) of the following questions.

A.                 Describe the difference between mechanistic and empirical modeling

B.                 Is a first order reaction always faster than a zero order reaction?  Explain.

C.                 Sketch out a qualitative concentration vs distance (downstream) profile for a river with a point discharge at x=0 and a distributed source that runs from x=3 to x=6 miles.  Show qualitatively how increases in the 1st order decay rate for a pollutant changes this profile.

D.                 Explain the relationship between Secchi-disk depth and lake trophic state.  Why is there such a relationship?

E.                  Describe 3 different methods for determining stream velocity.

F.                  Describe 2 different ways of measuring drainage basin area

G.                 Describe the factors that determine re-aeration in rivers, and contrast this with the factors that determine re-aeration in lakes.  In your description, relate micro-scale processes (molecules) to macro-scale (bulk water or air)