JOURNAL OF ACRKETtML RESEARCH 
DEPARTMENT OF AGRICULTURE 
Vol. V Washington, D. C., March 6, 1916 No. 23 
FLOW THROUGH WEIR NOTCHES WITH THIN EDGES 
AND FULL CONTRACTIONS 1 
By V. M. Cone, 
Irrigation Engineer , Office of Public Roads and Rural Engineering 
CONTENTS 
Page 
Introduction. 1051 
Laboratory equipment and methods. 1053 
Experiments with notches having free flow.. 1059 
Conditions of notch edges required to insure 
free flow. 1088 
Distance from notch at which head should be 
measured. 1090 
Page 
Effects of different end and bottom contrac¬ 
tions upon discharges . 1091 
Relation of lengths of notches to discharges.. 1098 
Submerged rectangular and Cipolletti notches 1101 
Summary. 1107 
Literature cited. ina 
INTRODUCTION 
The developments in irrigation agriculture in the arid West have caused 
many changes to be made in the method of delivering water to canals 
and to individual irrigators. The value of water increases with the 
increase of irrigated acreage, and the long-accepted practice of fixing the 
charges for water on a per-acre-per-annum basis is rapidly losing ground 
in favor of charges based on the volume of water delivered. When irri¬ 
gators pay according to the amounts of water used, there is every incen¬ 
tive for them to study the water requirements of their crops and to use 
the least quantities they judge to be necessary. This leads to a proper 
economy in the use of water, permits a greater acreage to be irrigated 
with the available water supply, and conserves the land. 
The transition from a flat rate to a rate based on the water actually 
used is calling for a better knowledge of the accuracy and practicability 
of existing measuring devices as well as the development of new devices. 
‘ The weir is generally considered an accurate device for measuring water, 
and it doubtless is such, provided it is properly installed and the correct 
formula is used for determining the discharge through the notch. Weirs 
constitute a large proportion of the devices in use for measuring irriga¬ 
tion water at the present time, being principally of the rectangular notch 
1 This paper is based on experiments conducted in the hydraulic laboratory at Fort Collins, Colo., under 
cooperative agreement between the Office of Experiment Stations of the United States Department of 
Agriculture and the Colorado Agricultural Experiment Station. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
cs 
Vol. V f No. 23 
Mar. 6,1916 
D—s 
(1051) 
