Problem:
A family in Tucson Arizona has a house with an orange tree in the back yard. The tree has a 28 ft. diameter canopy and requires on average 170 liters of water per day. The family would like to capture rainfall to irrigate their orange tree (it would save a lot of money on their water bill). Tucson, Arizona receives an average of 309 mm precipitation per year.
Requirement:
Question 1: Assuming an average year and a collection efficiency of 0.85, what volume of irrigation water can be provided by rainfall harvesting from their roof (a catchment area of 230 m2).
Question 2: Assuming that the family uses a storage tank that is sufficient to retain all of the captured rainwater each year; will they have to purchase additional water from the utility company to meet the irrigation demands of their orange tree?
Note: Please show how to work it out.