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Section 785.19(d) Continued. <br />r 1 <br />LJ <br />Chatacteiistics"Sdppoitirig Essential Hydrologic Fdnctions <br />The first sub3ect area, the Illinois River floodplain, was found by <br />field investigation to be sub-irrigated. The essential hydrologic <br />function of sub-irrigation ie supported by the ability of the <br />alluvial valley floor to collect, store, regulate and make ground <br />water available to agriculturally useful plants year-round. The <br />characteristics of the Illinois River floodplain which support <br />sub-irrigation are: 1) high water table; 2) permeable alluvial <br />material; 3) high storage capacity in the alluvium; 4) perennial <br />source of water; and 5) water quality adequate for agricultural <br />use. A high water table is evident in the Kerr Tipple Area because <br />the water table is above ground level in the marsh surrounding the <br />tipple for most of the year. The permeability and storage capacity <br />of the alluvium is sufficient to store, regulate and transmit <br />alluvial ground water to the root zone. The main source of water <br />is from the perennial Illinois River, which transmits water to the <br />alluvium by flooding during the spring runoff season and by perco- <br />lation through the streambed at other times of the year. Alluvial <br />ground water quality, while moderately high in sodium and total <br />dissolved solids, is adequate for use in irrigating, farming, or <br />grazing land, as shown in Table 6, Kerr Mine Area Ground Water <br />Quality Data. <br />The second subject area, the Canadian River floodplain, is current- <br />ly flood irrigated. The essential hydrologic function of flood <br />irrigation is supported by surface water availability. The role of <br />the alluvial valley floor in collecting, storing, regulating and <br />making surface water available to agriculturally useful plants is <br />dependent on the following characteristics: 1) perennial source of <br />water; 2) diversion structures used for irrigation; 3) surface <br />water quality adequate for agricultural use. The Canadlan River is <br />a perennial stream with an average baseflow of 4 cubic feet per <br />second, as shown in Figure 8, USGS Canadian River Flow Hydrographs. <br />785-34 <br />