Asking "what's the chance of rain" has acclimated everyone who watches the news to the concept of risk. The goal of this work is to enable tools for watershed managers, stakeholders, and the public alike to be able to evaluate the risk of water contamination within watersheds. Presented in this dissertation are three methods of risk analysis using reliability methods. First, Load Resistance Factor Design (LRFD) is applied to watersheds to develop reliability based design equations. Second, risk maps of watershed are created using first order approximation. Third, a Monte-Carlo (MC) procedure is used to perform system reliability analysis, create sensitivity maps, and create sustainability metrics including reliability, vulnerability resilience, and the sustainability index. These methods help to address watersheds which are complex systems and water quality which is driven by inherently stochastic environmental processes. These tools will give watershed managers means to evaluate the risk of water contamination and help make decisions regarding management.