Central Columbia Plateau - Yakima River Basin NAWQA Study -- Publications
USGS Fact Sheet FS-080-97
by Moon H. Kim and James C. Ebbert
October 1997
Irrigation and Surface-Water Quality
in the Quincy and Pasco Basins, Washington
Highlights:
- The transition from furrow to sprinkler irrigation has reduced the transport
of soil from irrigated cropland to surface waters.
- Both current conditions and historical trends reveal that decreasing use
of furrow irrigation reduces the soil loss.
- Lower concentrations of DDT in streambed sediment and fish tissue were
detected in drainage basins with lower percentages of furrow irrigation.
- Decreasing use of furrow irrigation may reduce runoff losses of other
pesticides and nitrogen from irrigated cropland.
During 1993-94, scientists with the U.S. Geological Survey National Water
Quality Assessment (NAWQA) Program collected samples of surface-water
discharges at the outflows of nine drainage basins containing irrigated
cropland. All or parts of the drainage basins lie within the Quincy and Pasco
Basins of Washington State. The study area is defined by the boundaries of the
Columbia Basin Irrigation Project where irrigation water is diverted from the
Columbia River and distributed to cropland through an extensive network of
canals and laterals. Samples were analyzed for concentrations of suspended
sediment, pesticides and nutrients. Usually, the effectiveness of an
irrigation method in reducing surface runoff is assessed with small-scale
studies on plots and fields. The data from this NAWQA study provided an
opportunity to assess the effects of the two dominant methods of irrigation,
furrow and sprinkler, on the runoff of soil, pesticides and nitrogen from
irrigated cropland to surface waters at a drainage-basin scale. Using
historical data, the relation between changes in methods of irrigation and
changes in soil loss over time was also evaluated.
Land use and sampling sites (GIF, 33173 bytes)
Irrigated agricultural drainage basins sampled in the Quincy and Pasco Basins
[mi2, square mile]
_____________________________________________________________________________
Site Drainage Irrigated Furrow
abbrevi- area area irrigation
ation Sampling site (mi2) (mi2) (percent)
_____________________________________________________________________________
CCL000 Crab Creek Lateral 56.2 39 44
E68001 EL68D Wasteway a 146 52 78
ESQ005 Esquatzel Wasteway a 475 72 14
FRC006 Frenchman Hills Wasteway 202 80 27
LCC005 Crab Creek near Beverly 386 93 43
LIN008 Lind Coulee Wasteway a 703 35 58
MAT001 Mattawa Drain 18.1 13 0
P16000 PE16.4 Wasteway 118 44 19
SAN004 Sand Hollow Wasteway 46.5 31 22
_____________________________________________________________________________
a = Parts of drainage areas extend outside the study area.
How Does Irrigation Affect Surface-Water Quality?
Surface-water quality is degraded by the runoff of
soil, pesticides and nutrients from cropland to streams. Runoff of soil and
associated compounds from cropland typically increases when surface runoff
increases as a result of precipitation or irrigation. Sprinkler irrigation
usually produces less surface runoff than furrow irrigation. Therefore the use
of sprinkler irrigation reduces the runoff of soil and may reduce the runoff of
pesticides and nutrients from irrigated cropland and their transport to surface
waters.
Decreasing
Use of Furrow Irrigation Results in Less Soil Loss
Analyses
of samples collected from nine drainage basins during April and May 1994 at the
beginning of the irrigation season indicate that yields (amount discharged
divided by acre of irrigated cropland) of suspended sediment, an indicator of
soil loss, are closely related to the percentage of cropland irrigated by the
furrow method.
Downward
Trend in Use of Furrow Irrigation Over Time Has Decreased Soil Loss
Analysis of long-term data for one site, Crab Creek near
Beverly (LCC005), shows a strong relation between yields of suspended solids
and the percentage of cropland irrigated by the furrow method. (Suspended
solids and suspended sediments are differentiated by the techniques used to
collect and analyze the samples. The concentration of suspended solids are
usually less than suspended sediment.)
Decreasing
Use of Furrow Irrigation Provides Additional Benefits to Surface-Water Quality
In a related study in the
Quincy and Pasco Basins, Gruber and Munn (1996) found that drainage basins with
lower percentage of cropland irrigated by the furrow method had lower
concentrations of DDT in streambed sediment and fish tissue. To determine if
runoff losses (amount discharged divided by amount applied) of other pesticides
and nitrogen also relate to the irrigation method, samples were collected and
analyzed at two sites during the 1993 irrigation season. Results indicate that
runoff losses of most pesticides and nitrogen in the Crab Creek Lateral
drainage basin (CCL000), with a lower percentage of cropland irrigated by the
furrow method, were less than losses from the EL68D Wasteway drainage basin
(E68001) (see following table).
Comparison of runoff losses from two basins sampled in 1993
__________________________________________________________________________
Furrow Runoff Losses:
irrigation Pesticides Nitrogen
Sampling site (percent) (percent) (percent)
__________________________________________________________________________
Crab Creek Lateral (CCL000) 44 a 0.04 5.6
EL68D Wasteway (E68001) 78 a 0.31 8.4
__________________________________________________________________________
a = Median value of 13 pesticides.
Other Management
Practices Can Reduce Soil Loss
Although this fact sheet showed the effects of irrigation method on soil
loss and runoff losses of compounds, other management practices can also
influence soil loss from irrigated cropland. For example, adding polyacrylamide
(PAM) to irrigation water increases the cohesiveness of soil particles, making
the soil less subject to erosion (Raloff, 1993). Since 1995, PAM has been used
extensively on cropland irrigated by the furrow method in the study area.
References
Gruber, S.J. and Munn, M.D., 1996, Organochlorine pesticides and PCBs in aquatic ecosystems of the Central Columbia Plateau: U.S. Geological Survey Fact Sheet 170-96, 4 p.
Raloff, J., 1993, Holding on to the Earth: Science News, v. 144, p. 280-281.
USGS Fact Sheet FS-080-97
By Moon H. Kim and James C. Ebbert
October 1997
This fact sheet is based on the journal article by Ebbert, J.C. and Kim, M.H.,
in press, Relation between irrigation method, sediment yields, and losses of
pesticides and nitrogen: Journal of Environmental Quality, [about 8p.]
For further information, contact:
Project Chief
CCYK NAWQA
1201 Pacific Ave., Suite 600
Tacoma, WA 98402
Phone:(253) 593-6530 ext 2687; -6514 fax
Email: rwblack@usgs.gov
Suggested citation:
Kim, Moon H., and Ebbert, James C., 1997, Irrigation and surface-water quality in the Quincy and Pasco Basins, Washington: U.S. Geological Survey Fact Sheet FS-080-97, on line at URL http://wwwdwatcm.wr.usgs.gov/ccpt/pubs/fs.080-97.html, accessed [date of access].
For a paper copy of this report, send
Email to rwblack@usgs.gov
Central Columbia Plateau
- Yakima River Basin NAWQA Study
National Water-Quality Assessment Program || NAWQA Program bibliography
Water Resources of Washington State || U.S. Geological Survey
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