1) (20 points) Determine the evapotranspiration rate in the drainage basin of the Peconic River (Eastern Long Island) by using the hydrologic balance equation and discharge and precipitation data.
a) Download the discharge and precipitation data for the Peconic river at Riverhead, and three precipitation stations in the area: Bridgehampton, Greenport Powerhouse, and Riverhead Research Farm. The data are in tabulated text format (.TXT). Save the file and open it in EXCEL. Make sure to save it immediately as an EXCEL file, e.g. PECONIC.XLS. Look at a map that shows the location of the streamgage (Riverhead, Long Island).
b) (6 points) Plot the discharge rate and the precipitation at Riverhead as a combination diagram with two Y-scales as a function of time. Discharge should be plotted as a line, precipitation as bars. Make sure that the axes are properly labeled. Print the graph.
c) (4 points) Explain in a few sentences the relationship between discharge and precipitation.
d) (4 points) Make the best estimate of total precipitation for the drainage area using the data for the three weather stations. The size of the drainage area is given in the data file.
e) (6 points) Determine the average evapotranspiration rate
for
the two given months using the precipitation and discharge data given.
Assume that the groundwater is in steady state, i.e. there is no change
in storage. How much (%) of the precipitation is lost by
evapotranspiration
in the basin? Tip: your answer should be in the range of 1 to 100%.
2.) (10
points)
Measurement of changes in volume of water in an evaporation pan
is a
standard technique for estimating potential evapotranspiration. United
States Class A evaporation pans are cyclindrical with the following
dimensions: depth = 10.0 inches, and diametrer = 47.5 inches. An
evaporation pan can be considered a hydrological system with an inflow,
outflow, and storage volume. Evaporation from pans is not the same as
evaporation from natural surfaces for a range of reasons. For example,
water temperatures in shallow pans will be much more variable than
temperatures in a nearby lake. Evaporation measured in pans is adjusted
by a factor called a pan coefficient to convert to an estimate of
potential evapotranspiration.
b) Calculate the flux of latent heat from the water in the pan to the atmsophere (W m-2).