How is a sand dam different from other rainwater harvesting methods?

Sand dams are one of the lowest cost rainwater harvesting techniques, costing less than both underground and above ground tanks per 1,000 litres of water provided. Costs are kept down by the fact that communities contribute to every sand dam project (e.g. by providing basic construction materials and labour), but also because sand dams require little to no maintenance, and have no operational costs.