Laserfiche WebLink
1 <br />1 <br />1 <br />1 <br /> <br /> <br /> <br /> <br /> <br />1 <br />1 <br />[~ <br />flow regulations altered the timing, duration, and magnitude of annual flood flows. <br />F'eak discharges in many areas of the Colorado River system have been reduced by <br />~~bout 50% since 1942, and base flows have been increased by 21 % (Fradkin 1984). <br />C)iversions from the river systems begin at or above tree line in most sub-basins:. In the <br />upper Colorado basin, transmountain diversions take water out of the basin. This water <br />is~ diverted for agricultural, municipal, and industrial uses, and is also lost from the <br />system by evaporation from reservoirs. Consumptive use data for the river system <br />suggest that, if water usage equates to habitat, fish have to survive on 60% less <br />basinwide, and much less than 60% at specific locations within the system. Flow <br />depletions constitute a major threat to endangered fishes in some areas. For example, <br />hiistoric aquatic habitats once maintained in important tributaries, such as the Salt and <br />Gila, may now be dry. <br />Construction of large impoundments has changed the distribution of riverine and <br />lacustrine habitats in the basin over a very short time period. The effect is more <br />pronounced in the lower basin. Historically, portions of the Colorado River system <br />have had extensive floodplains that were inundated seasonally. The seasonally <br />flooded bottomlands, marshes, and oxbow lakes once were a normal feature of the <br />river system, and presumably were important habitats in the life cycle of the razorback <br />sucker. <br />27 <br />