2.1. Study Area
The SRR is located in south-central Utah and is a tributary of the Green River in the upper CRB (Figure 1). Like many desert river tributaries in the arid southwestern United States, the SRR has experienced a number of anthropogenic perturbations like dams, diversions and intensifying climate shifts. These impacts have significantly altered its natural hydrograph of high-magnitude, long-duration spring snowmelt-driven floods and short-duration, monsoon-driven floods in late summer and early fall (Webb & Betancourt, 1990; Fortney, Schmidt, & Dean, 2011; Laub et al., 2013). The presence of reservoir and water-diversion systems upstream on the SRR’s three tributaries causes the SRR to be one of the most overallocated basins in Utah, where these reservoirs can hold back all spring runoff with exception to those years with abundant snowfall and snowmelt (Fortney et al., 2011). Another significant impact to the SRR riverscape includes the invasion of nonnative tamarisk and Russian olive (Elaeagnus angustifolia ), which has contributed to vertical accretion of fine sediments, enhanced streambank stabilization, channel narrowing and planform simplification (Manners, Schmidt, & Scott, 2014). The loss of a natural flow regime, as well as the invasion of nonnative vegetation, has caused the SRR to change from heterogenous, diverse and multi-threaded system to a highly aggraded, simplified and homogenous riverscape (Walker & Hudson, 2004; Pennock et al., 2021;). Specifically, between 1938 and 2009, the system has narrowed 83% in the lower 90 km, and the floodplain has vertically accreted between 1.0 and 2.5 m (Fortney et al., 2011). Reduced flow and exacerbated channel simplification have also collectively altered habitat for native and endemic fishes, significantly reducing the quality and availability of complex habitat required for spawning, feeding, resting and rearing necessary for their persistence (Bottcher, Walsworth, Thiede, Budy, & Speas, 2013; Walsworth, Budy, & Thiede, 2013).