2) (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%.
3) (10 points) A spill of a hazardous chemical has occurred on a road parallel to a river. Two rows of wells were installed parallel to the road/river. The hydraulic head of all wells in row 1 (near the road) is 200m and in row 2 (near the river) 150m. The contaminated water is flowing from the spill site towards the river. The wells of row 2 are planned to be used to pump the contaminated water away so that it does not reach the river. The pump rate must be at least as high as the rate of groundwater flow towards the river.
a) (5 points) Calculate this rate by using Darcy's law. The hydraulic conductivity is 1x10-3m/s, the distance between the two rows of wells 2000m, the thickness of the aquifer 100m and the width of the aquifer 1000m.
b) (5 points) The road is 2000m distant from the wells in row 2. How much time will pass after the spill until the contaminated water will reach the wells in row 2? The porosity of the aquifer is 0.3. (time = distance/velocity!)