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Section 5 <br />transfer involving a 1 in 5 year fallowing, 125,000 to <br />330,000 acres of agricultural land would be needed <br />in the fallowing program to produce 100,000 AF of <br />firm annual yield. Storage would also be associated <br />with this alternative and the volume of storage <br />required is specific to the irrigation company <br />system. It is estimated that 100,000 to 200,000 AF of <br />storage could be required to produce 100,000 AF of <br />firm annual yield that would be delivered every year <br />including during extended drought periods. <br />Under a rotational fallowing, 125,000 to <br />330,000 acres of agricultural land would <br />be needed in the fallowing program to <br />produce 90,000 AF of firm annual yield. <br />Conceptual schematics of an agricultural pumpback <br />diversion are shown in Figure 5-14. This figure <br />illustrates the likely components of the water <br />diversion system and firming storage system for a <br />South Platte or Arkansas agricultural transfer <br />alternative. <br />Addressing the Water Supply Gap Technical Roundtable <br />Water quality in the lower reaches of the South <br />Platte and Arkansas Basins is not suitable to directly <br />provide for drinking water supply using <br />conventional water treatment processes. There is <br />limited opportunity to exchange the transferred <br />agricultural water upstream to points of diversion <br />where water quality is higher and compatible with <br />standard water treatment processes. Total dissolved <br />solids (TDS) in the South Platte range from <br />approximately 700 milligrams per liter (mg/L) in the <br />Brighton area to over 1,000 mg/L downstream of <br />Greeley. In the Arkansas, TDS also progressively <br />increases as the river flows downstream Removal of <br />TDS greater than 500 mg/L and other constituents <br />of concerns such as hardness, nitrates, and organics <br />will require advanced water treatment processes. <br />Due to low water quality, alluvial pretreatment <br />(bank filtration) is assumed as a pretreatment step <br />for organics removal and to precondition the water <br />for advanced membrane processes such as reverse <br />osmosis. A comparison of a conceptual treatment <br />process for conventional treatment of higher quality <br />water and two advanced treatment processes for <br />treating TDS supplies with higher TDS or organic <br />carbon are shown in Figure 5-15. <br />River <br />Diversion <br />o`~ <br />Alluvial <br />Wellfield <br />Delivery <br />to <br />New Use <br />Figure 5-14 <br />Conceptual Schematic of Diversions and Firming Storage for Agricultural Pumpback Alternative <br />FINAL DRAFT 5-21 <br />Pipeline to Water <br />Treatment & <br />Terminal Storage <br />