8.4.1 Step drawdown tests

In a step drawdown test，the well is pumped at several successively higher pumping rates and the drawdown for each rate is recorded.The entire test is usually carried out within one day.Usually，5 to 8 pumping rates are applied，each lasting 1⁃2 h.

Figure 8.16 displays the relationships between pumping rates and drawdowns in a hypothetical case.As shown in the figure，line45is of steeper slope than line123.Obviously，when the pumping rate is equal to 90 m3／h or 100 m3／h，the drawdown in the well increases substantially and the well is in the condition of overpumping.The pumping rate at the intersection of line123 and line45is thus the capacity of the well.

Figure 8.16 Relation between drawdowns and pumping rates for a step drawdown test