Evaluation of scraping treatments to restore initial infiltration capacity of three artificial recharge projects in central Iran

 A limiting factor in developing artificial recharge of groundwater is clogging of the soil surface and consequent reduction of infiltration rates. In order to evaluate the degree of improving infiltration rates by scraping away various amounts of the upper soil materials, a study was conducted at three artificial recharge sites (Kohrouyeh, Bagh-Sorkh, and Kachak) in Isfahan Province, central Iran. Five treatments (T1–T5) were considered. Infiltration was measured: T1, on deposited sediment layer; T2, after removing the sediments; T3, scraping of sediments and 5 cm of soil; T4, scraping of sediments and 10 cm of soil; and T5, removing sediments and 15 cm of soil. Initial soil-moisture content of the sites ranged from 1.0–2.87% for Kohrouyeh, 1.18–3.47% for Bagh-Sorkh, and 1.89–3.93% for Kachak. The main texture of the soils was sandy loam. Clay particles have penetrated to a depth of more than 40 cm in some of the recharge basins. A significant increase in final infiltration rate of T5 as compared to T1 treatment was observed for all recharge sites. The final infiltration rates of T1 and T5 treatments for Kohrouyeh, Bagh-Sorkh, and Kachak sites were 0.35, 7.9; 1.22, 12.3; and 0.93, 6.2 cm/h, respectively. The differences between infiltration rates of T2, T3, and T4 treatments were not statistically significant. It is concluded that on average, the infiltration capacity of the untreated recharge facilities have reached 20.3% of the original values, and that scraping the top sediment layer and 15 cm of topsoil could restore 68.3% of the initial infiltration capacity. Received, July 1998 / Revised, April 1999, May 1999 / Accepted, June 1999