Introduction 



Populations of many native fishes in the western United States have declined in 

 part because of entrainment in irrigation ditches (Schill 1984; Fleming et al. 1987; Der 

 Hovanisian and Megargle 1998). In the Blackfoot drainage of Montana, unscreened 

 irrigation ditches are common within the range of bull trout {Salvelimts confluentus), 

 which is threatened (63 FR 31647) under the ESA (USFWS 2002), and westslope 

 cutthroat trout {Onchorynchus clarki lewisi) a species of special concern in Montana 

 (Pierce et al. 2002). Blackfoot tributary assessments have identified irrigation ditches on 

 47 of 89 inventoried streams (Montana Fish, Wildlife and Parks files). As a tool to assist 

 recovery of native fish populations, resource agencies, conservation groups and irrigators 

 are screening irrigation diversions in order to minimize population losses due to ditch 

 entrainment. Screening irrigation ditches in the Blackfoot River drainage had contributed 

 to increased fish densities in tributary populations as well as the overall densities of 

 imperiled native fish in the Blackfoot River (Pierce et al. 2002b). 



Although some states require irrigators to screen ditches, Montana relies on 

 voluntary compliance. In order for voluntary screening programs to be effective, fish 

 screening devices must first meet fish screening objectives and provide adequate water 

 supply for agricultural needs, operate effectively with little or no maintenance and must 

 be cost effective (Black 1998; personal observation). Although there are many options 

 for screening irrigation ditches (Odeh 1999; Nordlum 1996), barrier screens are often 

 expensive and require higher maintenance than many irrigators are willing to accept 

 (Mefford and Kubitschek 1997; Fleming et al. 1987; Black 1998; personal observation). 



Herein, we discuss the potential for a turbulent fountain, originally designed as a 

 self-cleaning trash remover (Bondurant 1983), and then modified as an effective fish 

 screen. A turbulent fountain screen consists of a circular, horizontal screen with a 

 vertical riser pipe in the center. The water flows up through the center pipe and spreads 

 laterally over the screen pushing fish and any entrained debris outward towards the edge 

 of the screen surface (Kemper and Bondurant 1985). Turbulent fountain screens operate 

 entirely with hydraulic pressure as a single integrated diversion structure and contain no 

 moving parts, require no external power and only minimal maintenance {See Bondurant 

 and Kemper (1985) and Kincaid (2002) for original descriptions and diagrams of 

 turbulent fountain screens). 



As with other types of barrier screens used for fish protection, the suitability of a 

 turbulent fountain screen varies with site conditions. A turbulent fountain is most 

 appropriate for small irrigation diversions with flows ranging from 0.03 -0.15 m^s, and a 

 moderate level of hydraulic differential between the intake and the fountain riser (e.g. 

 higher gradient streams; Kincaid 2002). Although turbulent fountain screens offer an 

 effective, low-maintenance option for screening debris from small stream irrigation 

 diversions (Bondurant and Kemper 1 985), the efficacy of turbulent fountains is untested 

 for screening fish. 



In order to assess efficacy for screening fish, we designed and installed a 

 prototype turbulent fountain fish screen on McCabe Creek, Montana. Our objectives for 

 evaluating the turbulent fountain fish screen were to: 1) determine the potential of a 

 turbulent fountain system for screening fish; 2) assess impingement (fish contact with the 



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