Estimated critical soil volumes are presented for a representative range of U.S. cities using the soil volume methodology. The tree used in this example has a crown diameter of 20’ and is about 35’ in height. Calculations were based on the nee having a crown projection of 314 fŕ with an average leaf area index of 4. The growing site is Ithaca, N.Y.
| CITY | EVAPORATION PAN RATE1Inches per month | ONE DAV SOIL VOLUME2(Ft3) | RAINFALL FREQUENCY3(Days) | TOTAL SOIL VOLUME (Pt3) If AWHC4 of soil Is eilher 15% or 19% | ||
|---|---|---|---|---|---|---|
| Ithaca, NY | 6.21” July | 28 | 10 | 300 | 220 | (.70 ftVft2 CP)5 |
| Seattle, WA | 7.00” July | 30 | 20 | 600 | 480 | (1-5 ft3/ft2 CP) |
| Mobile, AL | 7.19” May | 32 | 10 | 300 | 250 | (.80 ft¼2 CP) |
| Indianapolis, IN | 7.13” June | 33 | 15 | 500 | 400 (l.2ft’/ft≡CP) | |
| Minneapolis, MN | 7.88” July | 35 | 10 | 350 | 275 | (.87 ft¼2 CP) |
| Miami, FL | 8.03” July | 36 | 10 | 350 | 285 | (.91 f^/ft2 CP) |
| Denver, CO | 9.80” July | 45 | 15 | 700 | 525 | (1.7 fp/ft2 CP) |
| Phoenix, AZ | 14.83” June | 68 | 80 | 5400 | 43J5 | (14ft3/ft2CP) |
↵1 The highest mean mean monthly pen evaporation value for 20-30 years or data record for each city.
↵2 Assumes a soil available water holding capacity of 15%.
↵3 Defines the critical rainfall event A minimum of 92% of all dry periods (less than 1/10’ rainfall) lasted this num ter of days or fewer for etch dty. Derived ton 10 yean of data recced for each city.
4 WHC-available water holding capatity of the nil. This represents du faction of the total water, on a volume basis, thM it actually available (tx toot uptake. Two available water holding capacities are presented for comparison here, an average, 15% and a high. 19%. AWHC of any soil per can be ascertained tn a lab lest, and specified for use a the tree piL
5 Derived cubic feet of soil per square foot of crown projection.