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<br />. <br /> <br />03G,l <br /> <br />RECHARGE POTENTIAL <br /> <br />Infiltration Rates <br /> <br />An important factor in the consideration of artificial recharge is <br /> <br />the infiltration rate or rate at which water can enter the soil. Infiltra- <br /> <br />tion rates will depend upon water characteristics such as the amount and type <br /> <br />of suspended material and chemical constituents, and upon soil characteris- <br /> <br />tics such as texture or size of soil particles; soil structure or the <br /> <br />arrangement of soil particles; the resulting pore space and its distribution; <br /> <br />the continuity and stability of the pores; and chemical constituents. On a <br /> <br />reasonably uniform soil, the interface between water and soil at the soil <br /> <br />. <br /> <br />surface appears to be the zone controlling the infiltration rate (Schiff and <br /> <br />Dyer, 1965, P.H-6l, H-62). <br /> <br />In general, a decrease in infiltration rate is observed as recharge <br /> <br />takes place. Some of the factors include (1) swelling of the clay fraction of <br /> <br />the soil upon wetting, (2) air entrapment, (3) clogging action of microorgan- <br /> <br />isms and (4) deposition of suspended solids. Furthermore, recharge rates may <br /> <br />be retarded by perching of the percolating water caused by changes in the <br /> <br />lithology of the unsaturated zone (Gillespie, et al.,1977. P.23). Exhibit 5 <br /> <br />shows typical infiltration-rate curves for clear water and sediment laden <br /> <br />water. The increase in infiltration rate for the clear water curve is due to <br /> <br />~ <br />-D <br /> <br />the elimination of entrapped air as the recharge water percolates through the <br /> <br />sediments. The curve for sediment laden water is probably representative of <br /> <br />what would be experienced in the study area. <br /> <br />. <br />