Arkansas River Channel Capacity and Riparian Habitat Planning Study

Home Browse Search

1 ' especially between 1880 and 1910, and other water source alternatives were developed such as , P Y tapping ground and trans - mountain water (USAGE 1973:59; Milenski 1990:6 - 8,16 -27; Abbott 1985:8 -9). ' The preceding information brings us to a point from which we have a general understanding of some of the physical characteristics' of the Arkansas River and we have been ' introduced to numerous early historical 1800s events that have led to effects on the river that have culminated in the river we see today. While nature has a unique ability to overcome stress, by the end of the 1800s, the valley's vegetation and soils were in an extremely stressed condition. Through history then, there were several periods in which the floodplain grasses had been extensively overgrazed and their root systems %yere depleted to a point that it is nearly , impossible for the plant to survive, The upland prairie grasslands were also severely strained and the drought years were taking a toll. The stands of g1rand old cottonwoods that had grown to gigantic proportions during "the monsoon" years hack been cut down for firewood by the Native ' Americans and the huge influx of white people that traveled through or settled in the valley, and for railroad cross -ties and the smoke- belching locomotives. Many cottonwoods had also been cut down to feed large horse herds during the severe =winters and for building materials. The ' buffalo were nearly all gone and cattle have been introduced to take their place. Young cottonwood treei and other riparian vegetation were being grazed off almost faster than it could sprout. As in the many previous cycles of rain and drought, there is now little native riparian vegetation with significant root systems left in the volley to hold the soils during flood events. ' These poor conditions may have had some effects on the Arkansas River and be reflected in research by Nadler (1978:64 -65, 67, Table 11; USACE 1997:3 -5) where, in association with the Central PIains drought years of 1888 -1897 and the floods reported for the years 1885, 1886, and 1894, river sinuosity decreased between La Junta anal Las Animas and average river channel widths had increased from about 575 feet to 700 feet, between the years of 1870 and 1892. This is the river that was reported as a characteristically straight, wide, shallow braided channel. This ' would change, however, between 1926 and 1952 wh6n the channel "narrowed considerably" until "The 1952 width was only 21% of the 1892 width" (Nadler 1978:64). By the late 1800s, however, the canal systemo were starting to divert river water, as well ' as its suspended sediments, in significant amounts. It was not long before they were constructing sluice boxes in the canal downstream of the diversioO structures to try to flush at least a portion of the sediments back to the river in order to maintaii the canal (Watts and Lindner - Lunsford 1992:5). Now, during the irrigation season, the rive has such low flows that it could no longer effectively redistribute the flushed return sediments.: A Corps (1960) sedimentation report for the river above John Martin Reservoir indicated that ;as much as 5,000 acre -feet of sediment per ' year was being diverted from the river with irrigation waters, and that only about 20 percent of that sediment, about 1,200 acre -feet per year, was being returned to the river (and in Nadler 1978:90). The irrigation water diversions "temporarily reduced mean annual and peak discharges of the rivers" (Nadler and Schumm 1981 :197) and, along with other human uses that were also placing increasing demands on the river water, were beginning to make significant ' alterations to the river. Alterations were also occurring to the ground water table. Below the irrigation canals, the ground water table was rising a� the diverted irrigation water was utilized to 18 '