Water balance for a predominantly surface irrigated district in southern Idaho

Bjorneberg, D.L. and Nelson, N.O. and Westermann, D.T. (2006) Water balance for a predominantly surface irrigated district in southern Idaho. In: Proceedings of the 2006 World Environmental and Water Resources Congress. USA-NE-Omaha, 2006/05/21-25.

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Abstract

Water quantity and quality are being measured in an 82,000 ha irrigation district in
southern Idaho to determine the effects of conservation practices, primarily
conversion from furrow to sprinkler irrigation, for the Conservation Effects
Assessment Project (CEAP). The percentage of sprinkler irrigated land has steadily
increased from about 10% in 1990 to more than 30% in 2005. The objective of this
study was to calculate a preliminary water and soluble salt balance for April through
November, 2005. The water balance was calculated by subtracting measured outflow
and estimated crop water use from measured inflow and precipitation. Precipitation
was about 250% of normal in April and May, which delayed irrigation for many
crops and probably increased the amount of return flow during these months. Water
diverted for irrigation was 82% of the total water input to the irrigation district
(inflow plus precipitation). Precipitation contributed 16% of the total input. Thirty-six
percent of the diverted water left the irrigation district as surface return flow from
April through November. This percentage will increase on an annual basis because
return flow continues through the winter months after irrigation diversions have
ceased. The irrigation district was a source of suspended sediment and a sink for
soluble salts. April through November 2005 monitoring showed a net gain of 1620 kg
ha-1 of soluble salts in the irrigation district, which could be a long-term concern if
these salts accumulate in the root zone. Net sediment loss was 102 kg ha -1 , which is
less than the 461 kg ha-1 measured during a similar study in 1971. These preliminary
results indicate that converting to sprinkler irrigation, along with other conservation
practices, has reduced sediment loss from this irrigation district. However, solid
conclusions cannot be made until at least one year of monitoring is complete to
adequately characterize annual trends, particularly the quantity and quality of non-irrigation
season return flows.

Item Type:	Conference or Workshop Item (Paper)
NWISRL Publication Number:	1209
Additional Information:	2006 CDROM
Subjects:	Mass Import - unclassified
Depositing User:	Users 6 not found.
Date Deposited:	20 Nov 2010 21:56
Last Modified:	01 Nov 2016 15:07
Item ID:	959
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/959