Native Aquatic Species of the Gila River Basin
in Arizona and New Mexico
Drop Fish Barriers
A basic design for a drop barrier consists of a vertical concrete wall that rises 4-5 feet
above a concrete apron on the channel bottom (Figure 1). The crest wall typically follows
the configuration of the channel bottom so that a 4-5 foot drop extends across the entire
channel bottom (Figure 2). The apron is designed to produce uniform water velocities that exceed fish swimming
abilities, thereby precluding upstream passage. The vertical height of the barrier exceeds
the leaping abilities of fishes when combined with the shallow, fast-flowing water over the
apron. At high discharges, effectiveness of the vertical barrier will be lost in the center of the channel as water depths increase, but
the vertical drop will be maintained at the edges of the floodwaters where current
velocities are lowest. Upstream movements of fishes during floods are not expected in
mid-channel because of high current velocities and sediment loads, but potential movements
along the edges of floodwaters will be prevented by the maintained vertical drop. 
Figure 1. Conceptual View of a Fish Barrier
(Click on the Diagram above for full size version - .JNG approx. 43 kb)
Figure 2. Plan View of a Fish Barrier
(Click on the Diagram above for full size version - .JNG approx. 43 kb)
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Constructed barrier sites
Primary purposes
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| Aravaipa Creek | Protect existing populations of spikedace and loach minnow |
| Cottonwood Spring | Protect existing population of Gila topminnow |
| Fossil Creek | Replicate Verde River population of spikedace, replicate undetermined population of loach minnow |
| Tule Creek | Protect existing population of Gila topminnow |
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Proposed barrier sites
Primary purposes
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| Blue River | Protect existing population of loach minnow, replicate Eagle Creek population of spikedace |
| Bonita Creek | Protect existing population of Gila chub, replicate Eagle Creek populations of spikedace and loach minnow |
| Hot Springs Canyon | Protect existing population of Gila chub, replicate Aravaipa Creek populations of spikedace and loach minnow |
| O'Donnell Canyon | Protect existing population of Gila chub, replicate undetermined population of Gila topminnow |
| Redfield Canyon | Protect existing population of Gila chub, replicate Aravaipa Creek populations of spikedace and loach minnow |
| Redrock Canyon | Protect existing population of Gila topminnow |
| Sheehy Spring | Protect existing population of Gila chub, replicate undetermined population of Gila topminnow |
| Sonoita Creek | Protect existing population of Gila topminnow |
| Tonto Creek drainage (stream not yet selected) | Protect existing population of Gila chub, replicate East Fork White River population of loach minnow |
| Verde River | Protect existing population of spikedace, replicate Aravaipa Creek population of loach minnow. |
Last Reviewed:
May 28, 2008