Humans  activities are today’s major geophysical forces driving the Earth’s environmental changes. Over the past century, humans have altered various Earth system processes over a broad range of scales resulting in profound and often unprecedented negative environmental consequences, and freshwater systems are one of the most altered ecosystems. It is now well recognized that the water cycle is not natural anymore. Some of the most prominent and plainly visible impacts on freshwater systems are the changes in natural flow regimes, disappearance of large surface water bodies such as the Aral sea, and widespread depletion of groundwater resources around the world. On the one hand, the water cycle is continually changing in response to natural climate variability (climate change), and on the other hand, increasing human appropriation of freshwater systems is exerting additional pressure on already scarce water resources. Climate change and intensified extremes are further compounding these pressures, posing increasing challenges for sustainable management of food, water, and energy systems, and resilience of infrastructure and societal systems.

The foundation of my research framework is a quantitative modeling tool that holistically integrates various climatic, hydrological, societal, environmental, and agricultural systems. By taking large-scale climate drivers and human stressors (e.g., socio-economic changes, water management, nutrient loading) as input, the framework enables assessment and future projection of water supplies, demands, environmental flows, and floods and droughts, among many other dimensions crucial to address growing social and environmental problems and developing informed adaptation strategies. Technically, my research advances modeling capabilities for an improved understanding of changing water cycle within the Earth system and better assessment and projection of water resources (e.g., dwindling groundwater storages), agricultural productivity, and environmental shifts (e.g., nutrient loading and water quality). I have developed novel models to represent human dimensions (e.g., water management, crop growth and irrigation, groundwater pumping, reservoir regulation, and nutrient transport) in large-scale hydrological models and Earth system models (ESMs). Many of these new models are first of their kind and include innovative assimilation of big data from emerging satellite observations.

Over the years my research has, however, evolved largely from model-centric to transdisciplinary integration. My current projects include direct stakeholder engagement, inherent integration of socio-economic dimensions, and use of data science to leverage big data from new-generation satellites. Some of such recent crosscutting projects include the NSF grant on “Water and Environmental Sustainability in the American Southwest” and NSF/BELMONT Forum project on “Soils, Groundwater, and Societies”. Other projects aim to address the impacts of increased flooding in coastal and urban areas under intensified future extremes. More emerging research directions and proposal developments include convergent projects on socio-technical integration of climate change, shifting water demands, future energy needs, and resilience of transportation infrastructure. These new initiatives include collaborations with colleagues from energy, transportation, sustainability, and data science disciplines. Evidently, water and climate change are at the core of these problems; for example, climate change exacerbates the imbalance between future water demands and supplies directly impacting FEW securities, increased floods impede resilience of transportation systems, and growing energy needs for emerging transportation technologies compete with other water needs.

Despite major scientific advances made in modeling the changing water cycle under climate change, critical gaps remain in a holistic understanding of the intricately intertwined interactions between climate, water, society, and the environment, especially because of limited ability to model the compounding impacts of climate change and growing human stressors. My research uses a systems approach to address these challenges by using models and data that integrate hydrological, climatic, and socio-economic drivers into a holistic modeling framework comprising a suite of hydrological, agricultural, and ecological models. My research is inherently transdisciplinary and aims at integrating physical and/or engineering aspects of water cycle studies with socio-economic and environmental factors to address societal issues related to water and food security, while fundamentally advancing the understanding of the human-induced transformation of the water cycle.