ABE 325: Soil and Water Conservation Engineering. FINAL EXAM (250 points).
Open book exam. Calculators are allowed. Must show all calculations to.
ABE 325: Soil and Water Conservation Engineering FINAL EXAM (250 points) Open book exam. Calculators are allowed. Must show all calculations to receive credit for your work. Write your name on the top of each page. 1. Fill in the blanks or circle the most appropriate answer: (60 pt) a) Compaction of a dry soil causes a decrease / increase / no change in bulk density. b) Hardpans are caused by an excess of __________________ ions in the soil. c). List the four storm patterns based on rainfall distribution over time: _________________, ______________________, ______________________ & ______________________. d). Surface residues cause a decrease / increase / no change in runoff rates. e) A rainfall abstraction is water that is not available for: a. infiltration d. surface runoff b. evapotranspiration e. deep percolation c. surface storage f. all of the above f)
A hydraulic jump from supercritical to subcritical velocity causes a decrease / increase / no change in flow depth.
g) Which has a higher probability of occurring, a 10 year storm or a 50 year storm?______yr h) What is the common name for a radial flow pump? _____________________________ i)
Which of the following should not be used for drainage of alkaline soils? a. corrugated plastic tubing c. concrete tile b. deep surface ditches d. clay tile
j)
In surveying, a foresight is a rod reading on a point of known / unknown elevation.
k) Under the “Swampbuster” provisions of the 1985 and 1990 Farm Bills, it is illegal under any circumstance to drain a wetland: true false l)
Uniform channel flow: a. has a constant flow depth at a specific point over time b. has a constant depth of flow at all points along a channel c. is a local phenomena that occurs in conjunction with conservation structures d. describes the uniform backwater rise of water upstream of a dam
m) A wetland discharges / receives / discharges & receives water to and from the ground water table. n) List 3 benefits of irrigation: 1. 2. 3. o) List 3 benefits of drainage: 1. 2. 3. p). A farmer wishes to drain a field that forms a valley. Without any further information, which of the following drainage systems should he consider? a. grid iron subsurface drainage b. random surface ditches c. herringbone subsurface drainage d. parallel field laterals e. none of the above q). List 2 types of data suitable for GIS storage in vector format: ______________________ & _______________________. r) List 2 types of data suitable for GIS storage in raster format: ______________________ & _______________________. s) The amount of water applied through irrigation should be the same throughout a year in order to get proper root growth: true false t)
A farmer wishes to install a sprinkler system. Because he has many other duties he want a system that requires the minimum amount of labor. Which of the following systems should he choose? a. boom sprinkler c. self-propelled side-roll lateral b. giant gun sprinkler d. tractor towed lateral
u) What does GIS stand for? a. Geographic Information System b. Geographic Information Science c. Geologic Information Service
d. Geologic Information System
Use the following information to answer the remainder of the exam questions. Farmer Smith owns a farm near Lafayette, IN. The farm forms a single watershed. Smith is considering installing an irrigation system. As preliminary research he decides to investigate the hydrology of his farm. Some information about the farm that may prove useful: Land use
Area (ha)
Ave. slope (%)
Management
Soil Group
pasture corn soy
40 60 60
4 0.5 2
permanent up/down slope farming up/down slope farming
B B C
Assume good management. Soil: silt loam, void ratio of 1.2, good hydrologic condition, erosion resistant Time of concentration is 1 hour. 2. What depth of rain is expected to fall on this farm from a 25 year storm of 1 hour duration? (13 pt) 3. Smith places rain gages in the center of each field (i.e. land use) and records the following rainfall for a storm. What is the station-average rainfall for the storm? (10 pt)
Ppt (in):
Corn 2.3
Soy 2.4
Pasture 1.9
4. Using the Rational method, what is the peak runoff rate from the farm for a rainfall rate of 100 mm/hr? (20 pt) 5. Smith is concerned about soil erosion on his farm. List and very briefly define: (20 pt) a) 2 methods of reducing soil erosion due to surface runoff in the soy bean field b) 2 different methods of reducing wind erosion in the corn field 6. Smith decides to install a vegetated waterway to carry runoff from the soy field off to a small farm reservoir. Design a trapezoidal cross-section for erosion control ONLY that is capable of carrying 12 m3/s, uses Bermuda grass cut to 0.1 m, has 4:1 side slopes. Omit freeboard. Draw a sketch showing all dimensions and slopes. (40 pt) 7. Smith studies a topographic map to determine the storage capacity of the small reservoir. He records the following measurements with a planimeter for each given elevation. The map scale is 1 cm = 100 m. Draw a fully labelled stage-storage curve for the reservoir. (20 pt) Elevation (m): Map area (cm2):
78 0.2
79 0.6
80 1.0
81 2.0
8. Smith wants to use the reservoir water for a variety of purposes but is concerned about its quality. List 2 possible water contaminants from each land use area based on the type of land use. (12 pt)
9. Smith wants to drain a 16 ha square section of the corn field. He is considering subsurface drainage with CPT pipe. If he bases his design on a drainage coefficient of 13 mm and a drain slope of 0.2%, what diameter of commercial pipe should he install? (Can use equation OR graph to solve.) (15 pt) 10. Smith is considering installing a sprinkler irrigation system in the soy field. He would like to use a centrifugal pump operating at 950 rmp to supply water to the system. The pump he has in mind delivers 30 L/s discharge, and requires 14 kW of power when running at 1200 rpm against a head of 18 m. What are the theoretical discharge, head, and power values for this pump when operated at 950 rpm? (20 pt) 11. Smith decides to use furrow irrigation for his corn field. A pump is used to supply water into the irrigation canal at a rate of 58 m3/s. Due to evaporation and seepage losses, the water available at the edge of the corn field arrives at a rate of 48 m3/s. Drainage through the drain tile occurs at a rate of 1 m3/s and surface runoff is 4 m3/s. What are the conveyance, application, and beneficial use efficiencies? (20 pt)
