Colorado River. The Colorado River system serves as a source of water divided among 7 states for irrigation and domestic uses as well as for recreational activities, hydroelectric power, and environmental benefits. Most of the total flow into the Colorado River basin is a result of natural runoff from mountain snowmelt (USBR 2002). The Colorado River has undergone decades of alterations that have affected its ecosystems. These ecosystem alterations may have historically affected relict leopard frog populations through fragmentation of habitats and movement pathways, however, the extent of impacts are unknown. The closure of Xxxxxx Dam potentially created a barrier in gene flow between the Northshore population and the Black Canyon population of frogs as well as inundated existing habitat for the frogs. Coldwater releases from Xxxxxx Dam could potentially impact dispersal activities among the frogs, however, relict leopard frogs have been found downstream of Black Canyon at the Willow Beach National Fish Hatchery. These coldwater releases may have created a barrier against invasion by bullfrogs at Black Canyon which is beneficial to those populations of relict leopard frogs. Littlefield (including Xxxxx Springs) – The headwaters of the Virgin River originate in the Cedar and Pine Valley mountains in Utah (ADWR 1993). Annual runoff of the lower Virgin River consists of many sources including upper basin discharge, Xxxxxxxxxxx Springs inflow, Beaver Dam Wash discharge, and surface runoff from flood events (Xxxxxxx 1995). The origin of the Xxxxxxxxxxx Springs has been described by Xxxxxxx and Xxxxxx (1934), Xxxxxx et al. (1955), Xxxxxxx, (1979) and recently by Xxxxxxx (1995). Both Xxxxxxx (1979) and Xxxxxxx (1995) conclude that a portion of the flow from Xxxxxxxxxxx Springs is from Virgin River water, however, they each identified different sources for the remainder of the spring output. Xxxxxxx used major ion chemistry and tritium concentrations to describe the source of the Xxxxxxxxxxx Springs as local recharge and influent river water. Xxxxxxx used stable isotope data to rule out the local recharge component as being a potential source for the Xxxxxxxxxxx Springs. She concluded that groundwater was more likely a factor in contributing to the recharge of the Xxxxxxxxxxx Springs. The Southern Nevada Water Authority (SNWA) combined the tritium and stable isotope data of these 2 studies and concluded that the source of the Xxxxxxxxxxx Springs was a mixture of Virgin River wate...
Colorado River. The fish community sampling protocol established during Project 48-A (see Osmundson 1999) will be repeated in the 18-mile reach. At that time, the river from Rifle to Xxxxxxxxx was stratified by geomorphology and tributary input. On aerial photos, each of five strata was divided into multiple reaches, each consisting of one meander (xxxxxx-run) sequence 0.5-1.2 miles long. The reaches were numbered and three study reaches were selected within each stratum using a random numbers table. The 18-mile reach was one of the strata and the three study reaches selected within the 18-mile reach then will continue to be sampled for this SOW. Both shorelines will be sampled with boat electrofishing. To keep effort consistent with the earlier methods, two netters will be stationed at the front of each boat. Fish will be identified, measured for TL, and weighed. Two boats with a crew of three people each will be needed. One deviation from the earlier design, however, will be to reduce costs by sampling only once per year in the fall (Sep-Oct), instead of both spring and fall. Larval sampling will follow the protocol outlined above for the Gunnison River, extending from mid-May through the first week of August for razorback larvae. If at some point it is deemed feasible to begin sampling for larval Colorado pikeminnow, that sampling would occur from mid-June through the end of August (pending available funding, personnel, and equipment). The 18-mile reach and from Loma downstream to the Colorado-Utah state line will be sampled for comparison with results of Osmundson and Seal (2009). Fall YOY sampling will be restricted to the 18-mile reach and Loma downstream to the Colorado-Utah state line, following ISMP protocol with two seine hauls in each of two backwaters within each 5-mile reach (see XxXxx et al. 1994). The Principal Investigator will train crew members, act as overall crew leader and actively participate in data collection efforts. Along with annual data collection efforts, additional time will be required prior to field sampling to ready equipment and train new crew members in motor boat operation and field techniques specific to this project and later to input and check data.
Colorado River
