Water resource management under short term system perturbations such as storms and longer-term systemic changes caused by climate change such as droughts is challenge when multiple agencies are involved. Many semi-arid regions in western USA are experiencing rapid urban population growth, resulting in increase in water demand. At the same time, climatic changes in the hydrological processes have resulted in decreased water supply. These reinforcing changes have resulted in rendering the conventional urban water management approach of use-and-release as ineffective and a paradigm shift towards water reuse, water conservation, and water sequestration at an urban scale. With the adoption of new strategies by the urban water management agencies, the process of decision making has become complex due to interdependence and competition. In addition, the creation of specialized departments to monitor and manage different aspects of the water resource system led to the development of data management and computational systems within each agency focused on their own limited decision-making scope. However, the stakes for coordinated decisions are rising, especially in arid and semi-arid regions where the buffer between supply and demand is small. Uncertainty brought by future climate change, increased pressure on a range of natural resources, and growing demand make efficient decisions critical. At the same time, the potential for better integration across the water resource system has also increased, as more data are collected and computational power have advanced. This research focuses on improving the water management under changing climate conditions and population growth. This is achieved through understanding the agency water jurisdictions, management strategies, and modes of operation in Las Vegas Valley (LVV). The coupled behavior of supply water, stormwater, and wastewater in LVV is analyzed through a multi-agency point-of-view to identify ways to improve water efficiency and management efficacy. In this valley, Southern Nevada Water Authority (SNWA) is tasked with supplying water to Clark County from Lake Mead and groundwater pumping. Likewise, the job of Clark County Regional Flood Control District (CCRFCD) is to efficiently remove storm water from the urban area using a network of drains and detention basins. Similarly, Clark County Reclamation District (CCRD) treats the urban wastewater and releases into Las Vegas wash and thus, back into Lake Mead, the source of water supply for the LVV. Evidently, SNWA, CCRFCD, and CCRD have interrelations that could be used to improve an integrated water management of all types of water. For example, stormwater and treated wastewater can augment water supply. As a final product, a framework is presented that SNWA, CCRFCD, and CCRD can use to share data and models necessary for integrated water management. This framework, with appropriate modifications, can be used by other cities to improve coordination among different water management agencies resulting in better management of water resources.