please help with this hydrology homework! Fall 2017 Clearly highlight your answe
ID: 120162 • Letter: P
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please help with this hydrology homework!
Fall 2017 Clearly highlight your answers to each question/section/etc with the units. Include diagrams where required QUESTIONS BASED ON CHAPTER 9 1. These field notes were taken from a linear array of piezometers installed on a flat surface at a single site Piezometer elevation at ground surface (m) depth of piezometer (m) depth to water (m) 450 150 27 450 100 47 450 100 36 Calculate the a) hydraulic head, b) pressure head, c) elevation head, and d) pressure of the system. Hint: Drawing a diagram and plotting the different data on it may help 2. Given the following measurements at individual piezometers, calculate the a) hydraulic head, b) pressure head, c) elevation head, and d) pressure. Piezometer 100 100 55 320 80 65 120 40 210 20 10 ground surface elevation (m) 450 piezometer depth (m) 150 depth to water surface (m) 27 65 3·Three piezometers (A, B, and C) are screened in the same horizontal aquifer. Piezometer C is due south of Piezometer B and Piezometer A is due directly west of Piezometer B. The distance between A-B is 200 m, and the distance between A-C is 288 m. The surface elevations of A, B, and C are 95 m, 110 m, and 135 m, respectively. The depth to groundwater in A is 5 m, B is 30 m, and C is 35 m. a. Determine the direction of the groundwater flow through the aquifer. b. Calculate the hydraulic gradient in meters/meters. c. Include a diagram. Assume the map distance is 1 inch 100 m.Explanation / Answer
1) a) hydraulic head:
hydraulic head is nothing but the elevation of the water in the piezometer.Hence the elevation of water can be come by subtracting depth of water from surface elevation.
Surface elevation - depth to water
well 1
=450-27
=423m
well 2:
450-47
=403m
well3:
450-36
=414m
b) pressure head
pressure head is the height of the water above the depth of the piezometer above the datum.
Simply pressure head = depth of peizometer - depth to watertable
well1:
150-27
=123m
well2:
100-47
=53m
well3:
100-36
=64m
c)elevation head: it is the height of the measuring place within the peizometer above the datum.
= elevation of the surface - depth to peizometer.
well1:
450-150
=300m
well2:
450-100
=350m
well3:
450-100
=350m
d) pressure in the system :
p = hdg where h = height of the fluid or th edepth to the water
g= acceleration due to gravity
d= density of water
well1:
p = 27m *1000kg/m3 *9.8m/sec2
= 264600kg/metersec2 = 264600pascal
well2:
47*9800
=460600p
well3:
36*9800
=352800p
2)
a) hydraulic head : wellA) 450-27 = 423m
wellB: 100-65=35m
wellC) 320-55 = 265m
wellD: 65-40 = 25m
wellE: 210-10 =200m
b) pressure head :
wellA) 150-27 = 123m
wellB: 100-65 =35m
wellC: 80-55 =25m
wellD: 120-40 = 80m
wellE: 20-10 =10m
c)Elevation head:
wellA: 450-150 =300m
wellB: 100-100 =0m
wellC: 320-80=240m
wellD: 65-120 =-55m
wellE : 210-20 =190m
d) pressure in the system
wellA : 27*9800 =264600p
wellB: 65*9800 =637000p
wellC: 55*9800 =539000p
wellD: 40 *9800=392000p
wellE: 10*9800=98000p
3) b) hydraulic gradient = difference in hydraulic head between the wells/distance
hydraulic head at A = 95-5 = 90m
at B = 110-30= 80m
at C = 135-35 = 100m
hydraulic gradient at AB = 90-80 /200m
= 0.05m/m
at BC = 80-100 / 350 m {distance between BC comes from pythogorous theorem as we know two sides of a triangel as the three wells are place in the form of a triangle so , length2 (A) + length2B = C2 }
= 0.057m/m
At CA = 100-90 / 288 = 0.03m/m
a)ground water flows from high to low hydraulic head hence water flows from C to A to B
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