Three high flow experiment releases from Glen Canyon Dam on rainbow trout and flannelmouth sucker habitat in Colorado River

In recent years, dam management guidelines need to estimate the effects of downstream flow on environment. However, high-flow alters physical conditions such as water depth, flow velocity and water temperature in the downstream side of the river. These changes will lead to alteration in fish habitat of the river. In this paper, an eco-hydraulic model was used to determine the levels of fish habitat in the Colorado River downstream from the Glen Canyon Dam. This model has been proposed by combining hydrodynamic and heat transfer model with a habitat suitability index model based on fish preference curves. Rainbow trout (Oncorhynchus mykiss) and flannelmouth sucker (Catostomus latipinnis) were chosen as target species because they represent both native and non-native fish in the study area. Flow velocity, water depth and water temperature were selected as the suitability indicators. The hydrological data from three high-flow experiments were analyzed to determine the effects of high-flow on the Colorado River ecosystem. Numerical model simulations were undertaken as follows: firstly, based on the hydrodynamic and heat transfer equation, three hydraulic factors including water depth, velocity and temperature distribution were simulated and the associated suitability for each was obtained based on the fish preference curves. Later, the habitat suitability equation was developed to simulate the target species’ habitat situation in high flow effects. Finally, the WUA (weighted usable area) and OSI (overall suitability index) of the spawning fish species were quantitatively calculated to evaluate the sensitivity of the high flow. The results show that the effects of three HFE are more severe in spawning flannelmouth sucker than in spawning rainbow trout. It is worth noting that the one day HFE was beneficial to spawning rainbow trout and harmful to spawning flannelmouth sucker but in the HFE of more than 8 days, both the spawning habitats were completely destroyed.