Fate of suspended sediment during basin recharge

Suspended sediment in water used for recharge was tagged with the radioisotope 134Cs to determine the extent of its movement into materials underlying recharge basins and to aid in evaluating the effect of its accumulation on infiltration rates and the basin life. When openings of naturally occurring large pores were allowed to remain at the basin surface, 50% of the sediment suspended in the recharge water was moved deeper than 18 inches. However, when large‐pore openings at the surface were destroyed by cultivation, over 90% of the suspended sediment was filtered in the upper 1 inch. Most of this sediment could easily be removed at frequent intervals. The suspended sediment that moved deeper than about 0.15 inch, the depth removed at the end of each recharge cycle, has not noticeably reduced infiltration rates of a 0.1‐acre experimental basin.