Research on collective action and common pool resources is extensive. However, little work has concentrated on the effect of uncertainty in resource availability and collective action, especially in the context of asymmetric access to resources. Earlier works have demonstrated that uncertainty often leads to a reduction of collective action in the governance of shared resources. Here we assess how uncertainty in the resource availability may impact collective action. We perform a behavioral experiment of an irrigation dilemma. In this dilemma participants invest first into a public fund that generates water resources for the group, which is subsequently appropriated one participant at the time from head-end to tail-end. The amount of resource generated for the given investment level is determined by a payoff table and a stochastic event representing rainfall. Results show that access asymmetry and resulting inequalities dominate any effects from uncertainty about the resource condition. The strategic uncertainty about the decisions of other players dominates potential effects from the environmental uncertainty.