top of page
Research Highlights
Calibration-free PT method
Regional ET model
Water-Environment-Energy-Food Nexus
Calibration-free PT method
1/10
1. Evapotranspiration modeling & Regional and Global Irrigation Water Demand
Feb 2023, Water Resources Research
The Priestley-Taylor (PT) method is widely used in hydrologic and crop models to calculate the atmospheric demand for water or reference evapotranspiration (ETo). However, the default value of the PT coefficient (PTa=1.26) cannot assure reliability under different climatic regions. Su and Singh [2023, WRR] derived an analytical expression of PTa (PT_Su method) following the Penman-Monteith method. We provided the monthly PTa value at global scales with a spatial resolution of 0.25° using the daily Princeton Global Forcing dataset (1948-2016). The gridded global monthly PTa dataset is fully open-source [download] and can be incorporated into hydrologic and crop models to improve their ETo estimation using PT method. PT_Su method greatly improved the accuracy of ETo estimation using the PT method. We also provided simplified PTa under different climatic conditions for regional or local uses. Our findings have important implications for understanding the roles of radiative and aerodynamic components in global ETo changes.
December 2022, Agricultural Water Management
Su et al. [2022, AWM] evaluated the performance of three commonly used temperature-based methods, i.e., Thornthwaite (Th_T), Blaney-Criddle (BC_T), and Hargreaves and Samani (HS_T), and five radiation-based methods, i.e., Makkink (Ma_R), Priestley-Taylor (PT_R), Jensen and Haise (JH_R), Turc (Tu_R), and Abtew (Ab_R), for regional ETo estimates and calibrated them using the Penman-Monteith method using monthly meteorological data (1961–2010) from 15 weather stations in Texas, United States, covering humid, subhumid, semiarid, and arid climates. Here, we elucidated the controlling variables of ETo under different climatic conditions and how they are related to the structures of these methods. The HS_T method is recommended for regional analysis if reliable wind speed and relative humidity data are not available. We also adjusted the HS_T and PT_R methods by multiplying a calibration-free coefficient. By doing so, the accuracy of ETo under cool, dry, and windy conditions is considerably improved compared with the locally calibrated methods. The adjusted HS_T and PT_R methods can significantly improve the efficiency and accuracy of applying the less data-intensive ETo methods to predict regional or global irrigation water demand.
September 2022, Book Chapter
Fundamental to food security is irrigated agriculture and fundamental to irrigated agriculture is water security which is closely linked to soil security, energy security, health security, and ecological security. However, these securities are being threatened by climate change. Singh and Su [2022] address the role of irrigated agriculture in food security in the wake of climate change. Food production will have to increase by 24% by 2050 and by 40% by 2100 to ensure food security, assuming no change in consumption patterns. Irrigation capacity and technology efficiency will have to be increased, and at the same, food wastage and loss will have to be curtailed.
_tif.png)
July 2021, ASABE Annual Meeting Paper No. 2100540
Irrigation decision support tools can help crop producers improve the efficiency of the water they apply. However, the available tools generally have poor adoption rates due to high costs, extensive input data requirements, lack of economic analysis support, and/or low accuracy. Ale, Su, et al. [2022, ASABE Resource Magzine] developed an inexpensive and easy-to-use decision support mobile app called Irrigation Decision-support for Conserving Resources and Optimizing Production (idCROP) to aid cotton producers in the Texas Rolling Plains (TRP) regions to increase water-use efficiency while maintaining higher crop yields. Current global and regional seasonal weather predictions have a very coarse resolution, which limits their use in driving regional and local crop models. To overcome this issue, Su et al. [2021, ASABE Annual Meeting] developed an improved bias-corrected downscaling method to produce 1-km gridded daily seasonal weather forecast over the contiguous United States (CONUS). The downscaled seasonal forecasts at different lead times in local crop modeling were further evaluated using a calibrated crop model at an experimental station in the semi-arid TRP during the growing seasons of 2019-2020. The high-resolution seasonal weather forecasts generated in this study ensured robust and reliable regional or local crop yield and seasonal irrigation demand predictions in idCROP, which be directly integrated with other crop models.
July 2021, ASABE Annual Meeting Paper No. 2100541
To help producers choose deficit irrigation strategies that fit their well capacities and yield goals, Su et al. [2021, ASABE Annual Meeting] improved the Crop Water Stress Index (CWSI), a widely used method to indicate crop water stress and schedule irrigation, for sensor-based irrigation scheduling at Chillicothe station in the Texas Rolling Plains during the 2020 cotton growing season. The newly developed CWSI-PET model, representing potential evapotranspiration from a well-watered crop surface, outperformed the other three methods with less variability and uncertainty.
2. Modeling the Water-Environment-Energy-Food Nexus
January 2023, Environmental Science & Technology
Greenhouse gas (GHG) emissions from integrated urban drainage systems (IUDSs), including sewer, wastewater treatment plants (WWTPs), and receiving water systems, have not yet been integrated due to the lack of modeling tools. Su et al. [2022, ES&T] updated the computable general equilibrium-based System Dynamics and Water Environmental Model (CGE-SyDWEM), a recently developed model (Su et al., 2018) simulating the water–energy–carbon nexus at the watershed level, to calculate the direct and indirect (electricity use and external) GHG emissions from IUDSs considering carbon mitigation strategies and water engineering practices. The updated CGE-SyDWEM was applied to an estuary watershed in Shenzhen, the fourth largest city in China. The relative contributions of GHGs from sewers, WWTPs, and receiving water systems and their changes under carbon mitigation strategies and wastewater treatment and engineering practices were quantified for the first time.The integrated model can aid water, energy, and carbon decision-makers in finding cost-effective solutions for water and energy security in the future.
January 2019, Environmental Science & Technology
Carbon mitigation strategies have been developed without sufficient consideration of their impacts on the water system. Su et al. [2019, ES&T] evaluates whether carbon mitigation strategies would decrease or increase local industrial water use and water-related pollutants discharge by using a computable general equilibrium (CGE) model coupled with a water withdrawals and pollutants discharge module in Shenzhen, the fourth largest city in China. To fulfill China’s Nationally Determined Contributions (NDC) targets, Shenzhen’s GDP and welfare losses are projected to be 1.6% and 5.6% in 2030, respectively. We reveal that carbon mitigation accelerates local industrial structure upgrading by restricting carbon-, energy-, and water-intensive industries, e.g., natural gas mining, nonmetal, agriculture, food production, and textile sectors. This study highlights the importance of considering the energy–water nexus for better-coordinated energy and water resources management at local and national levels.
November 2018, Journal of Environmental Management
Energy and water systems are interdependent and have complex dynamic interactions with the socio-economic system and climate change. Few tools exist to aid decision-making regarding the management of water and energy resources at a watershed level. Su et al. [2018, JEM] developed CGE-SyDWEM to predict future energy use, CO2 emissions, economic growth, water resource stress, and water quality change at the watershed level. The effects of both the CO2 mitigation strategies and water engineering measures were evaluated. Our study improves the understanding of the feedbacks of CO2 abatement on water demand, pollutant discharges, and water quality improvement. CGE-SyDWEM can be used to aid energy, carbon, and water policy makers to understand the complicated synergistic effects of proposed CO2 mitigation strategies on water demand and pollution emissions, and to design more effective policies and measures to ensure energy and water security in the future.
Calibration and Application of the Receiving Water Module in CGE-SyDWEM
November 2014, Science of the Total Environment
Water supplement has been used to improve water quality in a heavily polluted river with small base flow. However, its adverse impacts particularly on nearby sensitive ecosystems have not been fully investigated in previous studies. Su et al. [2014, Sci. Total Environ.] employed Environmental Fluid Dynamics Code (EFDC) to evaluate the impacts of two potential water supplement schemes (reclaimed water scheme and seawater scheme) on water quality improvement and salinity alteration of the Shenzhen River estuary in China. The influences of salinity alteration on the dominant mangrove species (Aegiceras corniculatum, Kandelia candel, and Avicennia marina) were further evaluated by comparing the alteration with the historical salinity data and the optimum salinity range for mangrove growth.
December 2022, Indian Journal of Soil Conservation
The increasing demand for water, energy, and food poses significant challenges to natural resources and environmental sustainability. The concept of water, environment, energy, and food (WEEF) nexus offers an opportunity for integrated management of WEEF systems. Emphasizing the role of water in achieving the sustainability of WEEF security, Singh and Su [2022, Indian Journal of Soil Conservation] present the competition of water use, withdrawal, and requirement in domestic sector, food production, and energy generation and how climate change impacts the water availability for food and energy production. The nexus challenge and solutions to maintain the sustainability of WEEF are discussed. Engineering measures, such as adopting new technologies (particularly more efficient irrigation technologies) to improve water and energy use efficiency, and non-engineering measures, such as dietary pattern shifts and food waste reduction, are suggested as possible approaches. To achieve acceptable, equitable, and adoptable sustainability of WEEF security, we also suggest that water resources management simultaneously consider social, environmental, economic, and technological factors.
bottom of page