Successful formation and long-term stability of cooperative ventures is often linked to the perceived fairness of the cost and resource allocations that these ventures employ. Indeed, the lack of a consensus over what basis should be used for gauging equitable allocation can undermine the prospects for collaboration. We use irrigation cost sharing as a context for examining the equity basis selections of cooperative ventures that successfully form and endure. Our analysis reveals that these selections are explained by features of the cooperative environment and inequities in the derived benefits from the irrigation water.