The water crisis caused by climate change, population growth, high urbanization rate, lifestyle changes, and industrialization has decreased global access to safe freshwater resources. As the primary food-producing and the largest water-consuming sector, agriculture heavily depends on water availability. Incorporating alternative water supplies (e.g., water reuse) can reduce freshwater demands, addressing water crisis consequences. Water reuse generally includes recycling treated effluent (known as recycled water) from wastewater treatment plants for different applications (e.g., agricultural irrigation). This alternative water resource can reliably and sustainably increase the resiliency of agriculture to water shortage. However, the complexities inherent in water resources management and the challenges associated with water reuse make planning and managing agricultural water reuse practices demanding. Agricultural water reuse projects include many interrelated/ interconnected components, including the human (e.g., farmers) and technical (e.g., engineering and natural infrastructures) components. The abilities of existing models are limited in simulating these components’ complex and adaptive behaviors. It is necessary to utilize tools capable of capturing these complexities and adaptations to plan and manage agricultural water reuse practices sustainably.The main research question of this dissertation was: How to capture the complex and adaptive dynamics of socio-hydrological systems inherent in sustainable water resources management when alternative water sources are introduced in the water supply system? The primary focus of the dissertation was to develop a dynamic decision support system that can successfully simulate the complexities and adaptations inherent in agricultural water reuse practices. It aims at increasing the existing knowledge regarding agricultural water reuse planning and management and help water resource decision-makers make sustainable and better-informed decisions in agricultural water reuse practices. To accomplish this goal, first, the literature was thoroughly reviewed to identify, collect, and analyze the data related to agricultural water reuse (e.g., current agricultural water reuse regulations and guidelines). Second, two models were developed using a “bottom-up” approach to study two agricultural water reuse practices in the Southwest (CA) and Mid-Atlantic (MD-DE) regions. These two models were used to further study the dynamics of agricultural water reuse adoption by farmers and their impacts on local water resources. The results showed that the regulations and guidelines were mainly human health centered, insufficient regarding some potentially dangerous pollutants such as emerging constituents, and with large discrepancies when compared with each other. In addition, some important water quality parameters, such as pathogens, heavy metals, and salinity, were only included in a few of the regulations and guidelines investigated in this study. Finally, specific treatment processes were only mentioned in some of the regulations and guidelines, with high levels of discrepancy. Moreover, results showed that agricultural water reuse adoption by farmers is a gradual and time-consuming process. In addition, results also showed that agricultural water reuse could significantly decrease the water shortage (by 57.7%) and groundwater withdrawal (by 74.1%) in CA. The results also showed that climate change and recycled water storage capacity and unit price were among the top factors with significant influence on agricultural water reuse practice studied in this dissertation. This study demonstrated the importance of conducting time-varying sensitivity analysis for complex simulation models. Furthermore, results demonstrated that implementing agricultural water reuse could decrease farmers' water shortage, groundwater consumption, and surface water consumption (by almost 19.5 %) in MD. This dissertation’s results can help decision-makers effectively take advantage of agricultural water reuse projects and other alternative water resources to plan and manage water resources sustainably.