This dissertation is made up of three separate studies under the unifying theme of 0́−Water Decision-Making under Uncertainty.0́+ The first study analyzed a farmer0́9s decision to invest in a more efficient irrigation system given uncertainty about future water supplies and his post-investment efficiency. It found the price at which farmers would no longer produce to be a bigger consideration in irrigation investment than previously thought. It also found support for a careful identification and consideration of all significant sources of uncertainty in order to create better policy incentives for irrigation technology investments. The second study extended the first to allow the farmer to gradually update his irrigation system rather than undertake a single, complete overhaul. It found that giving the farmer this option, has significant impact and potential with regards to investments meant to effect behavioral change for improved system outcomes such as more efficient irrigation systems towards regional water conservation goals. The third and final chapter established a spatially explicit hydroeconomic model of water-use behavior in the Cache Valley of Utah to evaluate the impact of individual decisions, actions and interactions on available water supplies, and whether and how a water master0́9s privileged information about the behavior of users in his system may be used to improve system outcomes for users in the canal, downstream water requirements and storm-water management.