Question

1. Corn requires 22 inches of water for a successful crop. A farmer that has a 200-acre farm is in a drought and receives only 2 inches of rain throughout the year.
(a) Calculate how many gallons of water the farmer will need to purchase to be able to irrigate his crops. Recall that 60% of the water applied to a field through irrigation is lost. (An acre-foot is a common unit for measuring volumes of water, typically used in irrigation calculations. One acre-foot is the volume of water sufficient to cover an acre of land to a depth of 1 foot, approximately 325,851 U.S. gallons.) Show all work.


(b) Discuss two effects on a small stream if the farmer were to pump irrigation water from it, decreasing the flow rate of the stream.


(c) Discuss three ways the farmer could lessen the 60% loss of water while irrigating the farm.

Answer 1

Answer: Total volume of water corn needs= 22 inches x 200 acres = 1.833 fts x 200 acres = 366.6 acre-ft

Precipitation volume of water = 2 inches x 200 acres = 0.167 fts x 200 acres = 33.4 acre-ft

Water without lost in irrigation = difference in value = 366.6 – 33.4 = 333.2 acre-ft

The 40% used in irrigation as 60% waste is 333.2 acre-ft water.

Volume of water needed to be purchased = 333.2 * (100/40) = 833 acre-ft = 271433883 gallons (Ans)

[1 acre-ft = 325851 gallons]

The flow rate of water will decrease if the farmer has to pump water from a small stream.

b) Two effects on a small stream will be as follow-

1) There will be flow of ground water from the ground to the small stream.

2) Run-off rate will be higher to feed the small stream. So residence time of the water in the catchment will go down.

C) Ways that farmer could lessen 60% loss of water in irrigation

1) The farmer should increase the clay amount of the soil. Hence, water storing capability will be strengthened.

2) Increase the spatial density of plant can utilise more water to lessen the loss.

3) The drainage density should be decreased to lessen the loss of water and increasing the water-storage capacity of the farm.

Explanation: