[dgjrhgi]

Sand type definitely matters for water body ability to hold water. I have read articles where Indian ponds/lakes(used in older India for conserving water) were completely destroyed by Britisher's in attempt to clean them. They disturbed the existing floor composition leading to higher water percolation which dried the lake quickly.

[valarauko]

I doubt the ponds had sand, though. The size of sand particles is due to recent erosion and will continue to erode down to clay. Ponds and lakes are not capable of the level of erosion to create sand. Besides, sand is pretty poor at holding water. Remove the silt at the bottom of a lake clogging it up, and it'll percolate through much faster.