Chapter 2. Hydrology
21
Table 2. Ecosystem provinces of the western U.S. See Figure 3 for distribution of map
units.
Map unit
Ecosystem province
242
Pacific Lowland Mixed Forest Province
M242
Cascade Mixed Forest--Coniferous Forest--Alpine Meadow Province
M261
Sierran Steppe--Mixed Forest--Coniferous Forest--Alpine Meadow Province
262
California Dry Steppe Province
261
California Coastal Chaparral Forest Shrub Province
M262
California Coastal Range Open Woodland--Shrub--Coniferous Forest--Meadow Province
322
American Semidesert and Desert Province
341
Intermountain Semidesert and Desert Province
M341
Nevada-Utah Mountains Semidesert--Coniferous Forest--Alpine Meadow Province
342
Intermountain Semidesert Province
332
Great Plains Steppe Province
331
Great Plains--Palouse Dry Steppe Province
M333
Northern Rocky Mountain Forest-Steppe--Coniferous Forest--Alpine Meadow Province
Southern Rocky Mountain Steppe--Open Woodland--Coniferous Forest--Alpine Meadow
M331
Province
313
Colorado Plateau Semidesert Province
Arizona-New Mexico Mountains Semidesert--Open Woodland--Coniferous Forest--Alpine
M313
Meadow Province
321
Chihuahuan Desert Province
315
Southwest Plateau and Plains Dry Steppe and Shrub Province
Table 3. Summary of annual and monthly average depths of precipitation, revealing the
relative importance of different moisture sources throughout the study area (except
Texas). The statewide averages represent a weighted mean of the average precipitation
within each climate division located in a given state. (From www.wrcc.dri.edu.)
Average Depth of Precipitation (in.)
State
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Ann
AZ
1.10
1.01
1.19
0.54
0.35
0.29
1.86
2.07
1.34
1.06
0.99
1.30
13.10
CA
3.77
3.28
3.13
1.52
0.61
0.27
0.18
0.35
0.58
1.25
3.14
3.35
21.43
CO
0.72
0.72
1.20
1.27
1.80
1.51
2.03
1.87
1.42
1.13
0.93
0.87
15.47
ID
2.22
1.68
1.69
1.50
1.77
1.64
0.82
0.96
1.19
1.29
2.07
2.19
19.02
NV
0.87
0.84
0.94
0.78
0.90
0.73
0.58
0.72
0.68
0.67
0.89
0.86
9.46
NM
0.59
0.60
0.63
0.57
0.92
1.17
2.27
2.58
1.87
1.17
0.73
0.75
13.85
OR
3.90
2.94
2.92
1.94
1.64
1.26
0.52
0.82
1.13
1.99
4.01
4.26
27.33
UT
0.90
0.89
1.15
1.07
1.04
0.71
0.91
1.06
1.07
1.12
1.00
0.91
11.88
WY
0.63
0.55
0.82
1.33
1.94
1.71
1.24
1.01
1.17
0.91
0.73
0.65
12.69
Previous Page
