About

Ximing Cai has been a faculty member at the University of Illinois Urbana-Champaign's Department of Civil and Environmental Engineering since 2002. He teaches undergraduate and graduate courses in water resources engineering, surface water hydrology, application of geographic information systems, and river basin management. His primary research area is water resources systems analysis, with a focus on coupled hydrology-human systems. He develops and applies systems approaches and data-driven methods to various water management problems, including food-energy-water nexus, river basin management, reservoir operation, drought management, and interdependent infrastructure system planning. His work emphasizes interdisciplinary research by connecting hydrology and economics to understand environmental and water resources system complexity and to develop water management policies and solutions. Cai has been recognized for his contributions to hydrologic change accounting and water resources management, being elected as an AGU fellow in 2019 and receiving awards such as the 2023 Julian Hinds Award from the ASCE and the 2024 Warren Hall Medal from UCOWR. He has held academic positions including Colonel Harry F. and Frankie M. Lovell Endowed Professor in Civil Engineering and has served as a visiting professor at ETH Zurich. His consulting activities include work with international organizations such as the World Bank, OECD, and the International Food Policy Research Institute, focusing on climate impacts on agriculture, water and food security, and water management systems.

Research topics

• Geography
• Environmental science
• Computer Science
• Meteorology
• Geology
• Agroforestry
• Microeconomics
• Ecology
• Business
• Natural resource economics
• Cartography
• Climatology
• Statistics
• Geotechnical engineering
• Mathematics
• Economics

Selected publications

• pH-responsive, self-lubricating hyaluronic acid-chondroitin sulfate-chitosan hydrogel for articular cartilage repair

  Carbohydrate Polymers · 2026-05-11

  articleOpen access

  Cartilage degradation after joint injury often leads to post-traumatic osteoarthritis, a process accompanied by a drop in synovial pH. Traditional dynamically crosslinked hydrogels overlook how their mechanical and tribological properties change in such acidic, inflammatory environments. Here, we report an arthritis-responsive, injectable hydrogel designed to both regenerate articular cartilage and inhibit its further degradation. The hydrogel is formed via Schiff base chemistry between aldehyde groups of oxidized hyaluronic acid (OHA) and amino groups of adipic acid dihydrazide-grafted chondroitin sulfate (Chs-ADH) and carboxyethyl chitosan (CEC). Under neutral pH, the imine bonds remain stable, allowing precise defect filling and minimizing stress-induced debris; under acidic conditions, their reversible nature enhances lubrication and resists wear. The hydrogel formulation was optimized using molecular dynamics simulations to achieve excellent injectability, shear-thinning behavior, and low friction without impeding normal joint motion. In vitro, the hydrogel exhibited outstanding biocompatibility and stimulated cell migration. In vivo, it accelerated cartilage repair, prevented cartilage degradation, and restored the lubrication of newly formed tissue to levels comparable with healthy cartilage. Together, these findings demonstrate that the pH-sensitive hydrogel is a promising candidate for effective cartilage repair and prevention of cartilage degradation.

  PublisherDOI

• Extrapolability improvement of machine learning-based evapotranspiration models via domain-adversarial neural networks

  Environmental Modelling & Software · 2025-02-17 · 8 citations

  articleSenior author
  PublisherDOI

• Climatic and Socioeconomic Drivers of Water Use and Their Spatio‐Temporal Patterns for Small and Mid‐Sized Cities in the Contiguous United States

  Earth s Future · 2025-12-01

  articleOpen accessSenior authorCorresponding

  Abstract This study explores the drivers of urban water use and their spatial‐temporal patterns in 142 small and mid‐sized cities across the Contiguous United States (CONUS) by analyzing the data directly collected from these cities and using advanced machine learning techniques. We identify five distinguished clusters across CONUS, each showing unique trends of the impact of drivers on water use. We find that socioeconomic factors significantly influence water use in eastern and southwestern cities, while climatic variables such as precipitation and temperature range dominate in central and northwestern regions. Temporal analysis reveals the impacts of major socioeconomic and climatic disruptions on urban water use in the period 2011–2021, including the COVID lockdown, the rapid growth of data centers, and the drought of 2012. In addition, our analysis suggests that economic growth in small and mid‐sized US cities continues to be accompanied by rising water use, contrasting with the opposite trend observed in large cities in prior studies. This implies that as smaller cities develop, their water use may increase above current levels until incomes reach a higher threshold, highlighting the need to improve water use efficiency. This study also presents useful insights for developing effective water demand management strategies in response to climatic variability and socioeconomic growth in small and mid‐sized cities.

  PublisherOA PDFDOI

• Multi-Scale Impacts of Land Use Change on River Water Quality in the Xinxian River, Yangtze River Basin

  Water · 2025-05-20 · 6 citations

  articleOpen access

  This study investigated the impact of land use change on water quality in the Xinxian River Basin amidst rapid urbanization. While previous studies have predominantly focused on single-scale buffer analyses or specific land use types, the interactions between multi-scale riparian buffers and diverse land cover dynamics remain rarely understudied, particularly in a rapidly urbanizing county in the Yangtze River Basin. Land use type data for the Xinxian River Basin in 2000, 2010, and 2020 were acquired using GIS technology, and subsequent analysis quantified land use pattern changes over this 20-year period. Additionally, 2023 land use data for riparian buffer zones (50 m, 100 m, 200 m, 400 m, and 600 m) were obtained via GIS and subjected to Redundancy Analysis (RDA) with 2023 water quality monitoring data to evaluate the impact of land use on water quality. The results revealed significant land use conversion dynamics, particularly between natural and anthropogenic cover types. Forest cover exhibited negative correlations with riverine nutrient concentrations, while built-up areas displayed strong positive associations, especially at finer scales (50–100 m buffers). Notably, the dominant influencing factor shifted from built-up land at smaller buffer scales (50–100 m) to forest land at larger scales (400–600 m), whereas agricultural land showed no significant correlation. These findings highlight scale-dependent relationships between land use and aquatic ecosystems, emphasizing the critical role of spatial planning in mitigating urbanization impacts. The work is conducive to the sustainable development of Longgan Lake National Wetland Nature Reserve and the protection of water ecology in the middle and lower reaches of the Yangtze River.

  PublisherOA PDFDOI

• Data Centers Water Footprint: The Need for More Transparency

  2025-10-14

  preprintOpen accessSenior author

  The exponential growth of artificial intelligence (AI) has driven the rapid global expansion of data centers, raising serious concerns about their environmental impact—particularly water use. While national and global water consumption by data centers may seem modest compared to other users, their localized impacts can be significant—especially in regions already facing water stress or drought. This commentary examines the multi-faceted water footprint of data centers, encompassing direct cooling, electricity generation, and supply chain water demands. It highlights major gaps in transparency around how much water data centers use, which undermine effective regulation, innovation, and community planning. To ensure the sustainable growth of digital infrastructure and the preservation of water resources, comprehensive monitoring and public disclosure of water use are essential. Equally important are resilient water infrastructure planning and stronger collaboration between industry and communities.

  PublisherOA PDFDOI

• Fifty years of excellence in water resources research: insights from the most cited articles per decade published in <i>Water International</i>

  Water International · 2025-07-04 · 4 citations

  articleOpen access

  Yes

  PublisherOA PDFDOI

• Emerging Fields in Hydrology

  Journal of Hydrologic Engineering · 2025-02-07

  article

  Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

  PublisherDOI

• ENSO Enhances Seasonal River Discharge Instability and Water Resource Allocation Pressure

  Water Resources Research · 2025-01-01 · 2 citations

  articleOpen access

  Abstract The El Niño‐Southern Oscillation (ENSO) significantly disrupts Pacific Ocean watershed hydrology, affecting water supply reliability. However, the specific ways in which ENSO affects seasonal river discharge remain underexplored, presenting a significant gap in our understanding of climate‐water interactions. Our study reveals that ENSO exacerbates river discharge variability, evident in the dynamics of maximum rise (Dr) and fall (Df) in standardized discharge, and their duration (M). Notably, ENSO augments Dr but shortens M in major rivers like the Yangtze. Employing a novel metric, the Discharge Instability Index (DII), we find that DII surges by at least 69% in El Niño years, particularly in southwestern North American watersheds. Vegetation and precipitation emerge as pivotal in shaping the discharge response to ENSO. Predictive modeling with DII suggests an escalation in discharge instability under climate warming, with a 0.11%–9.46% increase. This insight calls for water managers to integrate ENSO‐induced seasonal variations into strategic planning, blending immediate actions like dam regulation with long‐term initiatives such as afforestation, to counteract climate‐induced water scarcity.

  PublisherOA PDFDOI

• Downscaling SDG6 (clean water and sanitation) to decision relevant scales

  Water International · 2025-07-04

  articleOpen access1st authorCorresponding

  Current efforts to localize Sustainable Development Goal (SDGs) are hindered by uncertainties and risk, insufficient monitoring and inappropriate indexes, and limited exchanges among countries/regions. We provide perspectives on downscaling SDG6 - clean water and sanitation -1 to decision relevant scales everywhere in the world. We synthesize existing experiences to identify promising approaches; test entry points and applicability of SDG indicators in pilot basins, cities, and countries; promote evidence-based indexes and dashboards for local water management. In this way, we directly respond to a key question of the UN 2023 SDG progress report on how progress towards SDG6 can be accelerated.

  PublisherOA PDFDOI

• Reachability of a Soil Phosphorus Target That Satisfies Agricultural Production and Water Quality Goals

  Water Resources Research · 2025-03-01

  articleOpen accessCorresponding

  Abstract Phosphorus fertilization has supported remarkable improvements in agricultural productivity but also degraded water quality. Watershed simulation models have been broadly instrumental to crafting phosphorus management responses. However, simulation‐based studies rely on predesigned watershed scenarios (e.g., initial conditions and management actions) and are blind to outcomes that might only emerge from unseen scenarios. Meanwhile, efforts to restore water quality have routinely failed. In contrast to simulation‐based methods, here we implement optimal control and reachability methods that describe watershed phosphorus trajectories for any initial condition and fertilizer strategy. The trade‐off is that these new methods require simplification of the system's dynamics. For a two‐pool phosphorus model, we define a dual management target where (a) plant‐available phosphorus satisfies crop demand but (b) total phosphorus losses meet water quality goals. From this target, we compute backwards‐reachable sets that indicate the minimum time in which the target can be reached from all initial conditions. For a typical watershed in the U.S. corn belt, we find that it will take at least 42 years to reach the joint agricultural and water quality target. We show that the optimal (time‐minimizing) fertilizer rate strategy drives a roundabout trajectory toward the target where soil phosphorus violates the crop demand threshold during the interim time. However, we find that even small, short‐term agricultural sacrifices can profoundly hasten progress toward the long‐term, joint target of agricultural productivity and water quality. These results and methods complement traditional simulation‐based studies and provide watershed managers with a richer characterization of uncertainty and management options.

  PublisherOA PDFDOI

Recent grants

• Planning for Drought Preparedness in the Watershed Context: A Risk-Based Decision Analysis

  NSF · $320k · 2008–2013

• EFRI-RESIN: Interdependence, Resilience and Sustainability of Infrastructures for Biofuel Development

  NSF · $2.0M · 2008–2014

• CAREER: Quantifying Environmental-Ecological Relationships for Watershed Sustainability Analysis

  NSF · $427k · 2008–2014

• INFEWS/T1: Advancing FEW System Resilience in the Corn Belt by Integrated Technology-Environment-Economics Modeling of Nutrient Cycling

  NSF · $2.4M · 2017–2023

Frequent coauthors

• Dingbao Wang

  University of Central Florida

  53 shared

• Mohamad Hejazi

  King Abdullah Petroleum Studies and Research Center

  47 shared

• Claudia Ringler

  International Food Policy Research Institute

  44 shared

• Mark W. Rosegrant

  International Food Policy Research Institute

  39 shared

• Yi‐Chen E. Yang

  29 shared

• Tze Ling Ng

  Commonwealth Scientific and Industrial Research Organisation

  22 shared

• Xin Li

  University of Chinese Academy of Sciences

  20 shared

• Pan Yang

  19 shared

Awards & honors

• 2019 AGU fellow for hydrologic change accounting for human i…
• 2023 Julian Hinds Award from American Society of Civil Engin…
• 2024 Warren Hall Medal from University Council of Water Reso…