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<br />I <br />I <br />I <br />I <br />I <br />~ <br />I: <br />I <br />I <br />I <br />I' <br />I <br />I <br />I \ <br />I <br />I <br />I <br />I <br />I <br /> <br />Kansas, is 5,572 square miles. Snowmelt in the upper reaches of the basin generally begins in <br />April, with the majority of runoff occurring from May through July. <br /> <br />The Colorado Water Quality Control Commission (1989, 1991) has classified benefIcial <br />uses and established basic quality standards for surface waters in the state. The Arkansas River <br />from immediately above the confluence with Fountain Creek downstream to the Colorado- <br />Kansas border is designated as "Use-Protected", that is, waters that do not warrant the special <br />protection provided by the High Quality 1 and 2 designations. lbis reach of the Arkansas <br />River has the following use classifications: <br /> <br />Class 2 warm water aquatic life - waters which are not capable of sustaining a wide <br />variety warm water biota due to physical habitat, water flows or levels, or uncorrectable <br />water quality conditions; <br />Secondary contact recreation - waters are those which are not suitable for prolonged <br />and intimate contact with the body; <br />Domestic water supply - waters which are suitable or intended to become suitable for <br />potable water supplies; and <br />Agriculture - waters which are suitable or intended to become suitable for irrigation of <br />crops and which are not hazardous as drinking water for livestock. <br /> <br />Numeric water quality and metal concentration standards that must be maintained in <br />surface waters in the study reach are described in Colorado Water Quality Control Commission <br />(1989, 1991) regulations. <br /> <br />Although surface water in most of the Arkansas River basin within Colorado is of a <br />quality suitable for most uses, mining in the headwater areas and irrigation in the primarily <br />agricultural lower basin have substantially degraded water quality in many reaches of the <br />system (Colorado Water Quality Control Division 1990). Generally, the concentrations of <br />dissolved solids, sulfate, total nitrogen, selenium, and suspended sediment increase in the river <br />from the headwaters to the Colorado-Kansas border. However, declining specific conductance <br />(an indicator of salinity and total dissolved solids) measured near the Kansas border between <br />1970 and 1989 is likely attributable to changes in water management and improved irrigation <br />practices (Middelburg 1993). <br /> <br />11 <br />