Utilizing Crushed Volcanic Scoria as a Subsurface Medium for Water Storage in Arid Regions: A Comparative Laboratory Study

Water storage systems face major challenges in arid regions, such as the Kingdom of Saudi Arabia (KSA), where high evaporation and seepage significantly reduce the efficiency of traditional open reservoirs. In addition, the construction of large steel and concrete tanks is costly, limiting their use outside urban areas. This study experimentally evaluates Crushed Volcanic Scoria (CVS) as a sustainable medium for subsurface water storage, and compares its performance with Crushed Granite (CG) and natural sand. Laboratory experiments were conducted using transparent acrylic cylinders to measure the Water Storage Capacity percentage (WSC%) and dry density across three particle size groups (16–12.5 mm, 12.5–9.5 mm, and 9.5–4.75 mm). For sand, three grain size types were tested for comparison. All materials were oven-dried, placed in cylinders, and saturated to determine their void-filling capacity. The results showed that CVS achieved the highest WSC% (72.7–62.8%), approximately 22% higher than CG and 30% higher than sand. The dry density of CVS (404.3–500.8 kg/m3) was markedly lower than that of CG (1532.8–1554.0 kg/m3) and sand (1468.7–1528.7 kg/m3), confirming its light and porous nature. These properties are attributed to the vesicular structure and irregular particle geometry of CVS, which result in higher porosity and water retention. Overall, it is demonstrated that CVS is a technically effective, economical, and locally available alternative for subsurface water storage in arid environments, reducing reliance on costly conventional storage systems.