Irrigation Water 
5 
Traps were set in a number of irrigation ditches in and 
about Fort Collins, Colorado. These included a large main 
ditch and several smaller ones. The data collected covered 
two seasons. 
The ditches from which the seed catches were taken are 
designated as: No. 1 (the Arthur ditch), No. 2, and No. 3, 
which are laterals from No. 1. 
The majority of catches were taken from No. 1 ditch whicli 
is, on the average, 12 feet wide, from 4 to 6 feet deep, and 
about 7 miles long, its source being the Cache la Poudre River 
two miles southeast of La Porte. The banks are steep and, in 
places, have been undermined by the current. The bottom of' 
this ditch is covered by a layer of fine, silty mud, ranging in 
depth from 3 to 14 inches. Ditches No. 2 and No. 3 are 2 to 
2 V 2 feet wide; 1 to 3 feet deep, and about IV 2 miles long. 
They have their sources from No. 1 ditch 1 mile apart. The 
bottoms of these ditches are rather sandy as compared with 
the bottom of ditch No. 1. 
The seed traps were set in No. 1 ditch only when the water 
was 3 to 4 feet deep, and in No. 2 and No. 3 when the water 
was 6 inches or more in depth. 
The velocity of the current varied from day to day. On 
those days on which the traps were set, the average velocity 
was 1 foot per second. 
INDIVIDUAL CATCHES OF WEED SEEDS 
The following typical cases give the number of species 
of weed seeds and the number of seeds of each species in indi- 
vidual catches. It will be kept in mind that the cross-section 
of water cut by the trap was a semi-circle, 3.36 square inches 
in area. 
TEST No. 1. DITCH No. 2. 
Date, June 1, 1918. Duration, 60 min. 
Species of weed seeds, 7. 
Number of seeds, 72. 
On pages 18, 14 and 16 will be found 
common names of the following plants. 
Chenopodium album 7 
Iva xanthifolia 3 
Polygonum aviculare 2 
Taraxacum officinale 5'6 
Verbena hastata 2 
Ambrosia trifida 1 
Leonurus cardiaca 1 
TEST No. 2. DITCH No. 3. 
Date, June 1, 1918. Duration, 80 min. 
Species of weed seeds, 10. 
Number of seeds, 35. 
Amaranthus blitoides 2 
Amaranthus retroflexus 1 
Chenopodium album 9 
Iva xanthifolia 1 
Iva ciliata 1 
Polygonum persicaria 1 
Rumex crispus 1 
Taraxacum officinale 16 
Grindelia squarrosa 2 
Ambrosia trifida 1 
