Hydrologic Budget Exercise
A. Write a hydrologic budget equation for each of the scenarios below, and calculate the change
in storage. Also write whether the hydrologic budget is at a loss, a gain, or at steady state.
I.
1.
2.
3.
4.
Precipitation = 72 in/yr
Evapotranspiration = 59 in/yr
Surface water Runoff = 9.6 in/yr
Groundwater pumping = 3.4 in/yr
II.
1.
2.
3.
4.
Evapotranspiration = 55 in/yr
Surface water Runoff = 9.6 in/yr
Groundwater pumping = 3.4 in/yr
Precipitation = 60 in/yr
III.
1.
2.
3.
4.
5.
Surface water Runoff = 9.6 in/yr
Groundwater pumping = 3.4 in/yr
Precipitation = 60 in/yr
Evapotranspiration = 55 in/yr
Groundwater inflow = 8 in/yr
IV.
1. Groundwater pumping = 0 in/yr
2. Surface water Runoff = 9.6 in/yr
3. Evapotranspiration = 55 in/yr
4. Precipitation = 60 in/yr
5. Groundwater inflow = 8 in/yr
V.
1. Groundwater pumping = 5 in/yr
2. Surface water Runoff = 9.6 in/yr
3. Evapotranspiration = 55 in/yr
4. Precipitation = 60 in/yr
5. Groundwater inflow = 8 in/yr
VI.
1. Groundwater pumping = 5 in/yr
2. Surface water Runoff = 23 in/yr
3. Evapotranspiration = 50 in/yr
4. Precipitation = 80 in/yr
5. Groundwater inflow = 8 in/yr
VII.
1. Groundwater pumping = 10 in/yr
2. Surface water Runoff = 23 in/yr
3. Evapotranspiration = 50 in/yr
4. Precipitation = 80 in/yr
5. Groundwater inflow = 8 in/yr
VIII. 1. Groundwater pumping = 10 in/yr
2. Surface water Runoff = 23 in/yr
3. Evapotranspiration = 50 in/yr
4. Precipitation = 80 in/yr
5. Groundwater inflow = 8 in/yr
6. Leakage from septic systems = 2 in/yr
B. Re-write the water balance equation for each of the scenarios above with the
units in terms of a volume per time (m3/yr). To report the water balance components
in terms of a volume estimate, multiply each of the parameters by the square area of
interest.
Our area of interest is Miami-Dade County, which is about 2,000 mi2.
2,000 mi2 = 5.5 x 1010ft2
As and example: Precipitation = 60in/yr ÷ 12 in/ft = 5 ft/yr x 5.5 x 1010ft2 = 2.75 x
1011ft3/yr ÷ 35.31 ft3/m3 = 7.8 x 109 m3/yr.
C. Complete a water budget for the Biscayne Aquifer of Miami-Dade County with
each of the components in units of million gallons per day (MGD).
Precipitation is 65 in/yr
ET is 55 in/yr
Runoff from the canals is 1.023 x 106 acre-feet/yr
Groundwater withdrawals is 331 MGD (million gallons per day)
Wastewater discharge back to aquifer in the form of septic systems is 1 MGD
Wastewater outfall to the ocean is 216.5 MGD
Wastewater injected into the Floridan Aquifer (deep well injection) is 97 MGD
The watershed size of Miami-Dade County is about 2,000 mi2.
a. What are the inputs? What is their sum?
b. What are the outputs? What is their sum?
c.What is the difference between the inputs and outputs?
d. Is the water budget in a steady state?
e. What parameters are missing from this water budget?
Delineating a watershed, estimating its area
Part 1. Delineating a watershed and estimating its area
A. Watersheds are delineated from topographic maps. Unfortunately the topography
of Florida is extremely flat and the underlying karst limestone results in nonconventional watersheds (i.e. there is no one stream through which all surface
water discharges). Therefore, you will be given a portion of a topographic map
from a mountainous area of Pennsylvania. On this map, draw the outline of the
watersheds for Bruner Branch and for Spicewood Run. Remember that the
boundaries of a watershed are designated by topographic highs. As you draw the
boundaries think about if a drop of water fell on the land which way would you
expect it to move? Towards the stream in your watershed or away? Use two
different colors to delineate these watersheds. Don=t worry that the southern
boundary for Spicewood Run is off the map.