Field Evaluation of Drop-Check Structures for Farm Irrigation Systems

Humpherys, A.S. and Robinson, A.R. (1971) Field Evaluation of Drop-Check Structures for Farm Irrigation Systems. USDA-ARS No. 41-180. 42 pp.

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Abstract

The slope of irrigated lands varies greatly, requiring
gradient control and energy-dissipating
structures in most irrigation systems. Water-level
control structures are also required for good
water management on irrigated farms. Combination
check and drop structures are often used
where both types of control are needed in the
same ditch. The headwall extension length and
cutoff wall depth requirements for these structures
vary for different soils and site conditions.
Most commercial structures of a given hydraulic
capacity have fixed dimensions and do not provide
sufficient headwall length or cutoff wall
depth for many field conditions. They also have
stilling basins that are generally too narrow or
too short or both. Washed-out structures and
eroded ditches are a problem on many farms.
A common standard design for a stable structure
at a given site is a formed, cast-in-place, concrete
structure. However, because of economy
and convenience of installation, prefabricated
structures are frequently used. Additional design
and site limitation information is needed to reduce
failures of prefabricated structures. Structures
are needed that provide adequate erosion
and water control, economy, ease of installation,
and ready acceptance by the farmer.
This study was made to obtain information to
improve the design of drop and check structures
for farm irrigation systems, and for use by the
USDA Soil Conservation Service and other
agencies in evaluating small structures. The
study involved the evaluation and comparison of
the field performance of various conventional
and standard structures as they are commonly
used. Several experimental structures were also
included. The hydraulic and structural characteristics,
together with installation and maintenance
requirements, were observed. The
amount of scour occurring upstream and downstream
from each structure, together with bank
erosion and undercutting, were observed
through four seasons of operation.

Item Type:	Technical Bulletin
NWISRL Publication Number:	0218
Subjects:	Mass Import - unclassified
Depositing User:	Dan Stieneke
Date Deposited:	20 Nov 2010 21:57
Last Modified:	17 Feb 2017 19:50
Item ID:	1109
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/1109