Stone covering factors influencing hillside pond interception and storage in a partial rainfall area

Abstract

In this study, a rainfall simulator was used in the laboratory to determine the interception capability of ponds with different percentages of stone covering (0, 5, 10, 20, and 30%) and different slopes (5, 10, and 20°). Red soil was placed on top of clean aquifer sand. A simulated semi-confined/semi-unconfined aquifer was formed in a soil tank connected with the rainfall simulator. Five ponds and five observation wells were dug along a red soil slope to measure groundwater levels, interception and storage of the ponds from rainfall runoff. The runoff collector (or a measuring tank) connected with the rainfall simulator was used to measure the surface runoff. The results showed that the interrelationships of the slope, percentage of stone covering, groundwater level, surface runoff, and the capability of interception and storage of the ponds were varied and irregular. No systematic patterns were detected for the changes in groundwater level, surface runoff, and capability of interception and storage of the ponds with different stone covering percentages and different slopes. No threshold values were apparent. For a 5°slope, an increase in the percentage of stone covering and a decrease in the amount of surface runoff and groundwater level increased the capability of interception and storage of the ponds. For a 10°slope, an increase in the percentage of stone covering and decrease in groundwater level decreased the amount of surface runoff and the capability of interception and storage of the ponds. For a 20°slope, an increase in the percentage of stone covering and decrease in the amount of surface runoff and groundwater level decreased the capability of interception and storage of the ponds. In addition, irrespective of the percentage of stone covering, and with hydraulic conductivity of the top material close to fine sand or red soil, an increase in slope gradient decreases the surface runoff and increases the storage of ponds.