Question

Problem 7. Unit Analysis and Engineering Design You have been hired to analyze the university's water usage. Much of the water used on campus goes toward irrigation. The only athletic field at Angelo State that requires irrigation is the soccer field. The daily irrigation demand, D in gal/day, can be calculated as ET,x F,x Ax0.62 D- E Where D-demand in gal/day ETo-Evapotranspiration factor (0.23 in San Angelo) Fp= Plant factor (ranges from 0.3 to 1.0 depending on type of plants being irrigated) A-Area being irrigated in ft E-Efficiency of the irrigation system (ranges from 0.75 for normal systems to 0.9 for drip irrigation systems 0.62 unit conversion factor You have been provided the following information. The grass used on the field is a bermuda/fescue/rye mix with a plant factor of 0.7. The total turf area is 1.9 acres. The current irrigation system uses normal pop-up sprinkler heads. The average annual temperature in San Angelo is 64.5°, the annual average rainfall is 20.45 inches, the average wind speed is 6 miles/hr, the average total degree day per year is 5133°F-Day. The field is used for practice and matches approximately 75 days/year. The average attendance at games is 67 people. Angelo state pays $13.00 per 1,000 gallons of water. One acre 43,560 square feet. One cubic foot 7.48 gallons. Compute the annual cost of water needed to irrigate the soccer field. Show all your work. a) b) The university has asked you to help reduce their water bills. Using the engineering design process, outline a plan to achieve the university's goal. Do not perform any computations for this part of the question. Simply outline the process you would use and identify the information you would need. Page 9 of 9

Answer 1

daily demand for irrigation can be calculated as D (gal/day) ETo Fr A*0.62 D = E Where ETo Evapotranspiration factor 0.23 for san Angelo Fp = Plant factor=1 for lawn A irigated area = 1.9 acre = 1.9*43560 = 82764 ft Efficiency for the irrigation system, for sprinkler irrigation take 80% E putting all value in above equation to get daily demand 0.23*1*1.9*43560*0.62 _ 14752.683 gallon per day D = 0.80 14752.683 13S= 191.78$ cost of irrigated water 1000

b) different engineering way to reduce water cost are

1) allow the water to irrigate by using natural force i.e gravitational force

2) using of water gel to retained moisture.

3) use shading to reduce sun heat

4) use wind screen to reduce wind speed

5) use wind sheet to capture early fog