Water-retention characteristics of coarse rock particles

Abstract

Water is retained on large particles of non-porous rock as a film of water about 0.1 mm thick on rock surfaces, as 0.006 to 0.180 ml droplets held at contact points between adjacent particles, and as small puddles of water on the upper surfaces of the rock. Water retained at contact points accounts for most of the water stored within aggregates of particles with diameters smaller than 30 mm. Whereas with diameters larger than 100 mm, water retained on the rock surfaces, particularly water puddled on top of the rock, accounts for most of the water. Infiltrating water will not wet all the rock surfaces. More than 50% of the surfaces may be dry at depth. The total amount of rainfall needed to initiate ground-water recharge in many areas having coarse rock particles at the surface is probably less than 1.0 cm.