Streamflow of 2012—Water Year Summary - USGSthe long-term annual mean for the United States (9.30...
Transcript of Streamflow of 2012—Water Year Summary - USGSthe long-term annual mean for the United States (9.30...
U.S. Department of the InteriorU.S. Geological Survey
FS 2013–3026May 2013
Streamflow of 2012—Water Year Summary
U.S. Geological SurveyReston, Virginia
May 2013
• Introduction• National Overview• Regional Patterns• Seasonal Characteristics• High and Low Flows
2012 Statewide streamflow
WetNormalDry
Introduction
The maps and graphs in this summary describe streamflow conditions for water year 2012 (October 1, 2011, to September 30, 2012) in the context of the 83-year period from 1930 through 2012, unless otherwise noted. The illustrations are based on observed data from the U.S. Geological Survey’s (USGS) National Streamflow Information Program (http://water.usgs.gov/nsip/). The period 1930–2012 was used because, prior to 1930, the number of streamgages was too small to provide representative data for computing statistics for most regions of the country.
In the summary, reference is made to the term “runoff,” which is the depth to which a river basin, State, or other geographic area would be covered with water if all the streamflow within the area during a specified time period was uniformly distributed upon it. Runoff quantifies the magnitude of water flowing through the Nation’s rivers and streams in measurement units that can be compared from one area to another.
Each of the maps and graphs below can be expanded to a larger view by clicking on the image. In all the graphics, a rank of 1 indicates the highest flow of all years analyzed.
National Overview
1930 1940 1950 1960 1970 1980 1990 2000 2010
Year
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5
10
15
Ann
ual m
ean
runo
ff (in
ches
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5
10
15
Annual mean U.S. runoff1930–2012
Average runoff in the Nation’s rivers and streams during 2012 (7.90 inches) was lower than the long-term annual mean for the United States (9.30 inches). Nationwide, 2012 streamflow ranked 69th out of the 83 years in the period 1930–2012. Note that in previous water year summaries (prior to 2011) the median runoff, not the average runoff, was compared among time periods.
2012 Statewide streamflow ranks1930–2012
AKHI
PR-VI
MA (45)RI (41)
CT (46)NJ (41)DE (56)MD (46)DC (47)
NHVT
28
28
25 2252
4833
60 4358
3858
62
603468
4561 1972 42
80 39 496466 45
7973
755655
63
41 82837460
4462
22
30
52 36
30*
Explanation - Rank 1 2–89–2064–7576–8283
Highest Muchabovenormal
AbovenormalNormal Below
normalMuchbelownormal
Lowest
21–63
Streamflow was at record low levels (ranking 83d in 83 years) in Georgia. Below-normal and much-below-normal streamflow was prevalent cross the Southeast, Midwest, and Southwest. Above-normal streamflow occurred only in Ohio. Most States had stream-flow in the normal range.
* For Puerto Rico, 69 years of available data were used.
Regional Patterns
Water resources regions of the United States
Water resourcesregions
The United States (including Puerto Rico) is divided into 21 large drain-ages, or water resources regions. These hydrologic areas are based on surface topography and contain either the drainage area of a major river, such as the Columbia, the combined drainage areas of a series of rivers, such as the Texas-Gulf region, which includes a number of rivers draining into the Gulf of Mexico, or the area of an island or island group. Water resources regions provide a coherent, watershed-based framework for depicting streamflow variations.
AKHI
PR-VI
28
61
3459
70 4547
6252
7436
7757
77 7759
555922
30
28*
Explanation - Rank 1 2–89–2064–7576–8283
Highest Muchabovenormal
AbovenormalNormal Below
normalMuchbelownormal
Lowest
21–63
Streamflows at much-below-normal levels were reported in the South Atlantic-Gulf, Rio Grande, and Lower Colorado regions. Below-normal conditions were measured in the Upper Mississippi and Upper Colorado regions.
Seasonal Characteristics
Autumn (October–December 2012) Statewide ranks
AKHI
PR-RI
MA (4)RI (3)
CT (4)NJ (4)DE (8)MD (8)DC (11)
NHVT
66
37
34 2057
271 415
41 920
312
64
13345
418 122 724 5 193453 7
6350
561532
71
10 8075535270
5034
46
36*
Autumn season (October–December) streamflow was at record-high levels (ranking first in 83 years) in Ohio. Above-normal and much-above-normal flows were reported in the Northeast, Great Lakes, and northern States, as well as a few western States. West coast States, Texas, Louisiana, Georgia, and South Carolina had below-normal and much-below-normal stream-flows. Nationwide, autumn season streamflow ranked 21st out of 83 years.
* For Puerto Rico, 69 years of available data were used.
Winter (January–March 2012) Statewide ranks
AKHI
PR-RI
MA (67)RI (70)
CT (64)NJ (69)DE (64)MD (61)DC (65)
NHVT
30
3634 28
4243
21 3929
36 4522
329
66
54 50659
38 3659 3231 45 555238 44
7273
564927
32
31 82836848
17
8345
29
9*
Explanation - Rank 1 2–89–2064–7576–8283
Highest Muchabovenormal
AbovenormalNormal Below
normalMuchbelownormal
Lowest
21–63
Winter season (January–March) streamflow was at record-low levels in Georgia and Florida. Below-normal and much-below-normal streamflows were reported in east coast States, California, Arizona, and Iowa. Above-normal conditions occurred in Wyoming, Utah, Louisiana, as well as Puerto Rico. Nationwide, winter season streamflow ranked 52d out of 83 years.
* For Puerto Rico, 69 years of available data were used.
Spring (April–June 2012) Statewide ranks
AKHI
PR-RI
MA (74)RI (72)
CT (70)NJ (71)DE (81)MD (76)DC (59)
NHVT
14
2922 56
4062
18 687558 798054
63
4575
755771
60 7671 7981 70 667067 79
8265
698274
73
81 81828281
69
5451
45
9*
Spring season (April–June) streamflow was below or much below normal in most States (37). Above-normal streamflow was seen only in Washington, Oregon, and Puerto Rico. On a nationwide basis, spring season streamflow was much below normal, ranking 81st in 83 years.
* For Puerto Rico, 69 years of available data were used.
Summer (July–September 2012) Statewide ranks
AKHI
PR-RI
MA (61)RI (56)
CT (60)NJ (47)DE (77)MD (54)DC (50)
NHVT
20
29
45 4154
5526 5267
78 6975
7470
49
385181
5483 6876 7581 59 558183 65
7455
81 6480
58
72 7177539
2520
53
41
46*
Explanation - Rank 1 2–89–2064–7576–8283
Highest Muchabovenormal
AbovenormalNormal Below
normalMuchbelownormal
Lowest
21–63
Summer season (July–September) streamflow in Midwestern and southeastern States—as well as Delaware, Vermont, and New York—was below or much below normal. Streamflows in Kansas and Nebraska were at record-low levels. Streamflow was above normal in Washington, Louisiana, and Florida. On a nationwide basis, summer-season streamflow was much below normal, ranking 76th in 83 years.
* For Puerto Rico, 69 years of available data were used.
High and Low Flows
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20
30
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30
2000 2004 2008 2012
Year
30
20
10
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30
20
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Perc
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amga
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Percentage of streamgages with very high and very low monthly streamflowOctober 1999–September 2012
2002 2006 2010
>95th percentile for month<5th percentile for month
In any given month, on average, it is expected that 5 percent of the streamgages will experience very high (>95th percentile) and very low (<5th percentile) average streamflow. During water year 2012, only 3 fall months (October, November, and December) had a greater-than-expected percentage of streamgages reporting very high streamflow (8, 7, and 8 percent, respectively). In contrast, there were 8 months (from February to September) with a greater-than-expected percentage of streamgages with very low flows (6, 6, 18, 8, 13, 13, 10, and 9 percent, respectively).
1950 1960 1970 1980 1990 2000 2010
Year
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10
20
30
40
50
60
70
80
90
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Perc
enta
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amga
ges
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10
20
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60
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80
90
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Percent of streamgages above bankfull streamflow1950–2012
The bankfull streamflow is defined as the highest daily mean streamflow value expected to occur, on average, once in every 2.3 years. In 2012, 23 percent of streamgages had a daily mean streamflow value above the bankfull level. This value is much smaller than the expected number (43 percent) to occur in any given year. Since 1950, the largest number of streamgages reporting higher-than-bankfull streamflow in any 1 year was 69 percent, which occurred in 1996.
1950 1960 1970 1980 1990 2000 2010
Year
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5
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15
20
25
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Perc
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f stre
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5
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15
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25
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Percent of streamgages below 10th percentile ofannual 7-day minimum streamflow
1950–2012
The 10th percentile 7-day low flow is defined as the lowest 7-day average streamflow expected to occur, once every 10 years. In water year 2012, 12 percent of the streamgages reported a 7-day average low flow less than the 10th percentile 7-day low flow value. The expected number to occur in any given year is 10 percent. Since 1950, the largest percentage of streamgages reporting a 7-day low flow less than the 10th percentile 7-day low flow was 25 percent in 1954.
Additional Information
The USGS operates a network of nearly 8,000 streamgages nationwide, most in real time. Current information derived from these stations is available at http://waterwatch.usgs.gov. Tables of data that summarize historical streamflow conditions by State, beginning in 1900, can be accessed at http://waterwatch.usgs.gov/?m=statesum. These tables are updated every few months to reflect the most current streamflow data.
The streamflow information used to prepare this summary is also used for water management, monitoring floods and droughts, bridge design, and for many recreational activities. To obtain real-time and archived streamflow data and information, visit http://water.usgs.gov/nwis. Although the national streamgage network is operated primarily by the USGS, it is funded by a partnership of 850 agencies at the Federal, State, tribal, and local levels. For more information about the streamgage network, visit http://water.usgs.gov/nsip/.
By Xiaodong Jian, David M. Wolock, Harry F. Lins, and Steve Brady
For additional information, contact:Office of Surface WaterU.S. Geological Survey415 National CenterReston, VA 20192http://water.usgs.gov/osw/
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