Abstract: It is significant for the mining watershed ecology to design protective coal pillar on surface runoff in ecologically fragile mining area. Taking Shennan mining area in Northern Shaanxi Province as research area, ecological carrying characteristics of watershed in desert shoal mining area have been investigated with methods of field geological investigations and sampling tests. Based on the research of development rules of water flowing fractured zone, limitations of traditional design for protective coal pillar have been analyzed. And a new method to design protective coal pillar, on the basis of watershed mining, has been proposed from the point of hydrodynamics of groundwater. The results have shown that on one hand surface runoff satisfies the most gross of ecological water requirement, as well as domestic and production water demand, but on the other hand 91.33% of surface runoff comes from ground water recharge in the sand layer. The water flowing fractured zone heights will reach 40.4 m to 69.2 m as first coal seam’s mining around drainage basins, and at the same time, sandy aquifer above goaf will drain off after mining. The new designing method based on watershed can avoid reverseseepage of surface runoff into goaf. The practical calculation has shown that the designed protective coal pillar is 62 m around Changjiagou River based on watershed, which is greater than 34.8 m of the traditional design for protective coal pillar.

Key words: water preserved mining, desert shoal, surface runoff, sandy phreatic water, watershed