ENDANGERED RIVERS - A CASE-HISTORY OF THE ARKANSAS RIVER IN THE CENTRAL PLAINS

1. This paper presents a summary of recent patterns of surface discharge in the Arkansas River in Kansas, and discusses the implications of dewatering on aquatic insect communities. 2. Significant reductions in surface flows of the Arkansas River have been observed since approximately 1974 in central and western Kansas. Dewatering of the river has been most severe between Syracuse and Great Bend, a distance in excess of 335 river kilometres, and has resulted in complete losses of surface flow for periods in excess of one year at several points along the river. 3. Minimum desirable stream flow (MDSF) standards developed and legislated by the state in the early 1980s have had little effect on reversing the trends associated with river dewatering. It must be concluded that dewatering has had substantial effects on aquatic insect communities through habitat modification in areas where surface flows are dramatically curtailed. These communities are extirpated, or nearly so, in areas where dewatering is most pronounced. 4. Reduction in groundwater withdrawals from the riverine aquifer and palaeochannels, some of which are considerable distances from the present-day river channel, must be considered in order to achieve MDSF during periods of dewatering. 5. Although it may be possible to achieve MDSF, it is argued that MDSF will not be sufficient to allow for development of habitats that are critical for restoration of 'natural' communities. A distinction is made between the ideal and the achievable as goals for a management strategy to conserve habitats for aquatic insects, and it is concluded that the ideal of managing surface flows to restore natural communities cannot be achieved in the light of recent reductions of surface flow and conflicting uses of groundwater for irrigation and minicipal consumption. As an alternative, concerted efforts must be made to ensure that MDSF is continuously achieved.