Research Highlights

The Role of Groundwater Withdrawals on River Regulated Flow

The primary research question addressed in this study is: How does groundwater pumping modulate the regulated streamflow in the CRB? The sensitivity of groundwater withdrawals to streamflow was performed using a modified version of the Variable Infiltration Capacity (VIC) model integrated with a water management component (VIC-IRR). The VIC-IRR version integrates a standardized method of irrigation with a reservoir module for dam release optimizations. Yet, the VIC-IRR version omits the consideration of groundwater availability when allocating the water needed for irrigation, which can have significant impacts on streamflow variability. We further augmented the VIC-IRR to include a third water management scheme that accounts for groundwater withdrawals and therefore allows for more supply options to irrigation demands (namely, VIC-GIRR version).


Reduction in total annual deficits after considering groundwater pumping (km3) at grid cells located upstream (a) and downstream (b) of each reservoir. (c) Reduction in total annual deficit (million m3) over the CRB. d) Total annual deficit in the grids located upstream and downstream of the American Falls Dam located at the upper Snake River. The deficit is calculated for VIC-GIRR 1234 scenario (GW has a priority of 2).

• Higher dam releases and storage fraction are simulated when groundwater withdrawals are considered.
• In dry years, deficits in surface water supply are offset by groundwater withdrawals.
• Future research directions include accounting for non-irrigation sectoral water withdrawals and impacts of climate change scenarios.

Scientific Focus Area (SFA): Integrated Modeling - Water System Dynamics

Reference: Eldardiry, H., Zhou, T., Huang, M., & Chegwidden, O. (2022). The Role of Groundwater Withdrawals on River Regulation: Example from the Columbia River Basin. Water Resources Research

Success Stories of Satellite Radar Altimeter Applications

For nearly three decades, satellite nadir altimeters have provided essential information to understand primarily ocean but also inland water dynamics. A variety of parameters can be inferred via altimeter measurements, including sea surface height, sea surface wind speeds, significant wave heights, and topography of land, sea ice, and ice sheets. Taking advantage of these parameters with the long record of altimeter data spanning multiple decades has allowed a diverse range of societal applications. In this paper, we review selected altimeter success stories that incorporate altimetry data, alone or in conjunction with numerical models or other Earth observations, to solve a key societal problem.


Timeline of the satellite radar altimetry missions since 1985.

• The growing constellation of altimeter satellites results in greater quantity (increasing record) and quality (increasing accuracy) of data and information products available to researchers and decision-makers.
• Development of altimeter-based datasets and the continued promotion of success stories at the global scale will support and highlight the potential societal applications of the forthcoming SWOT mission.

Scientific Focus Area (SFA): Remote Sensing

Reference: Eldardiry, H., Hossain, F., Srinivasan, M., & Tsontos, V. (2022). Success stories of satellite radar altimeter applications. Bulletin of the American Meteorological Society, 103(1), E33-E53. (DOI:

Satellite-based Framework for Modeling Reservoir Operation

This study presents the water management value of a modeling framework to predict the current and future reservoir operating rules in lower Nile basin using satellite earth observations and hydrologic models. The platform comprises the Variable Infiltration Capacity (VIC) hydrologic model driven by high spatial and temporal resolution of satellite observations. Reservoir storage change is estimated using altimeter and visible imagery of lake area for Lake Nasser and then applied to infer reservoir operation for High Aswan Dam (HAD).


Upper Panel: The discharge anomalies at Eldiem station (location of GERD dam in Ethiopia) averaged over the rainy season JJAS (June-July-August-September) during the period (1981–2017). Lower Panel: Operating curve of HAD for wet vs drought episodes using the satellite-based framework

• The hydrological modeling of the BNB shows high accuracy in simulating streamflow along the Blue Nile Basin (validated at Khartoum and Eldiem stations).
• Monthly HAD releases using satellite altimeter show good agreement with measured discharge downstream of the dam.

Scientific Focus Area (SFA): Integrated Modeling - Remote Sensing

Reference: Eldardiry, H., & Hossain, F. (2019). Understanding Reservoir Operating Rules in the Transboundary Nile River Basin Using Macroscale Hydrologic Modeling with Satellite Measurements. Journal of Hydrometeorology, 20(11), 2253-2269 (DOI:

Adapting High Aswan Dam Operation to Challenges of the Grand Ethiopian Renaissance Dam

The resilience of HAD operation to GERD construction typifies one of the challenges facing dam operators and water managers in downstream Nile riparian countries. Recently, various studies have investigated the impacts of GERD on downstream countries with more focus on the GERD filling strategies. However, crucial insights on how dam operators can adapt to potential impacts have not been capitalized in previous studies. Our study proposes a physical blueprint that employs water scarcity indices to infer modified reservoir operation that could adapt to streamflow alterations while maintaining the supply to downstream water use, i.e., water supply for irrigation and hydropower demands.


Schematic diagram of the blueprint proposed to re-evaluate the operation of existing dam under the filling/operation of an upstream planned dam.

• High Aswan Dam can adapt its operation in summer months by elevating the downstream stress level (store more and release less), to mitigate the effects of rapid GERD filling.
• A 7-year filling scenario by Ethiopia is minimally disruptive to operations of High Aswan Dam and results in faster recovery.

Scientific Focus Area (SFA): Integrated Modeling - Remote Sensing - Infrastructure Resilience

Reference: Eldardiry, H., & Hossain, F. (2020). A Blueprint for Adapting High Aswan Dam Operation in Egypt to Challenges of Filling and Operation of the Grand Ethiopian Renaissance Dam. Journal of Hydrology (DOI:

The Value of Long-term Streamflow Forecasts in Adaptive Reservoir Operation

Our study evaluates the use of long-term climate forecasts to improve real-time operations of High Aswan Dam (HAD) in the Nile river basin. A suite of eight models from North American Multimodel Ensemble (NMME) are used to generate monthly precipitation and temperature forecasts at up to 12 months of lead time. The NMME forcing are used to drive the Variable Infiltration Capacity (VIC) model and produce monthly streamflow forecasts for an optimization horizon of four years from 1998 to 2001. The value of NMME-based forecasts to reservoir operations are compared with perfect and climatology-based forecasts.


Forecast-based Adaptive Reservoir Operation (FARO) framework for deriving adaptive reservoir operating policy using streamflow forecasts

• The forecast horizon for HAD operation ranges between 8- and 11-month lead time at low and high demand scenarios, respectively, beyond which the forecast information no longer improves the release decision.
• Actual forecasts from NMME models can significantly improve the HAD operation with an average gain in forecast value of 77% compared to the climatology-based forecasts.
• When considering the operation of upstream Grand Ethiopian Renaissance Dam (GERD), using streamflow forecasts minimally helps to maintain current target objectives of HAD operation and therefore result in higher operation costs as opposed to current conditions without GERD.

Scientific Focus Area (SFA): Integrated Modeling - Infrastructure Resilience

Reference: Eldardiry, H., & Hossain, F. (2021). The Value of Long-term Streamflow Forecasts in Adaptive Reservoir Operation: The Case of High Aswan Dam in the Transboundary Nile River Basin. Journal of Hydrometeorology.

Small-Scale Catchment Analysis of Water Stress in Wet Regions of the U.S.

Using the state of Louisiana as an example, this study quantifies the stresses on water resources and investigates the potential for opportunities to use surface water in lieu of groundwater pumping. The assessment is based on a fine watershed scale (12-digit Hydrological Unit Code [HUC] boundaries) water balance between the availability of surface and groundwater and surface water and groundwater demand. Water demand includes environmental flows, as well as public supply, rural domestic, industrial, power generation, agricultural, and aquaculture sectors. The seasonality of water stress is also addressed by incorporating monthly variations in surface water supply and irrigation demands.


Water Supply Stress Index (WaSSI) on the HUC12 scale derived using annual average estimates of water supply and demand and a 50% environmental flow requirement (HUC12 watersheds with WaSSI less than 0.06 are displayed in white).

• The areas of the highest water stress in Louisiana are largely attributable to water consumption for power generating plants or irrigation.
• The stress analysis reveals a significant over-drafting/deficit of groundwater in many of the states aquifer systems.
• Seasonal fluctuations in surface water supply and water withdrawals for irrigation highlight the fact that the water system is under more stress during the summer season.

Scientific Focus Area (SFA): Integrated Modeling - Water System Dynamics - Infrastructure Resilience

Reference: Eldardiry, H., Habib, E., & Borrok, D. M. (2016). Small-scale catchment analysis of water stress in wet regions of the US: an example from Louisiana. Environmental Research Letters, 11(12), 124031. (DOI:

Energy-Water Nexus over the CONUS

The interactions between food production, energy production, and water supplies, sometimes referred to as the food-energy-water (FEW) nexus, are critically important to sustaining society. Two components of this nexus, energy and water, are strongly interrelated: Generating electricity and refining fuel require us to use water; pumping, delivering, and treating water require us to use energy. Links between the energy and water systems are expected to intensify in the future. Therefore, it is important to understand and foster continued attention to the interdependency between the systems in the water-energy nexus.


Using the energy-water nexus (HydroViz platform) to estimate net availability of water-for-energy resources and stresses on the water system (main panel) under different future scenarios of population growth, plant retrofitting options, and potential use of non-potable water resources (small inset).

• Increase in energy demand may infringe on water availability for other sectors, and it is important to explore if non-potable water resources can alleviate such infringement.
• Changing the plant cooling system (e.g., re-circulating, versus once-through), fuel type (e.g., coal, natural gas), or limiting greenhouse gas emission (e.g., via a carbon capture and sequestration, CCS) are primary factors to consider when assessing stresses on water system.

Scientific Focus Area (SFA): Integrated Modeling - Water Energy Dynamics - Infrastructure Resilience

Reference: Habib, E., Eldardiry, H., and Tidwell, V. (2017). New online tool teaches students about the energy-water nexus, Eos, 98. (DOI:

Carbon Capture and Sequestration in Power Generation: Impacts and Opportunities for Water Sustainability

Water is an integral element of Carbon Capture and Sequestration (CCS) processes. Since water is used for cooling and emissions scrubbing, deployment of CCS will potentially increase water withdrawals to meet the added needs for chemical and physical processes of capturing and separating large volumes of CO2. Thus, the CCS technologies are expected to significantly introduce additional stresses on the sustainability of water system.


Effects of primary cooling technology on plant water use at coal power plants with and without carbon capture and sequestration (CCS).

• CCS-equipped power plants have shown significant increases in water consumption in the range of 45 to 90 percent.
• The need for integrating the environmental, economic, and societal aspects of CCS deployment into future assessment of the viability of CCS operations.
• The extracted brine can potentially be used as a freshwater source to alleviate stresses in areas with water supply shortages.

Scientific Focus Area (SFA): Water Energy Dynamics - Infrastructure Resilience

Reference: Eldardiry, H., & Habib, E. (2018). Carbon capture and sequestration in power generation: review of impacts and opportunities for water sustainability. Energy, Sustainability and Society, 8(1), 1-15 (DOI:

Atmospheric River-Induced Precipitation and Snowpack during the Western United States Cold Season

In this study, we characterized precipitation and snow water equivalent associated with ARs intersecting the US western coast during the cold season (November through March) of water years 1949-2015. For each AR landfalling date, we retrieved the precipitation and relevant hydrometeorological variables from dynamically downscaled atmospheric reanalyses (NCEP/NCAR) using the WRF mesoscale numerical weather prediction model. Landfalling ARs resulted in higher precipitation amounts throughout the domain than did non-AR storms.


The average of upper 10th percentile daily precipitation over the western coastal domain during the winter (November to March) ARs for water years 1949-2015.

• ARs contributed the most extreme precipitation events during January and February.
• Daily snow water equivalent (SWE) changes during ARs indicate that high positive net snow accumulation conditions accompany ARs in December, January, and February.
• Analysis of ARs during dry and wet years reveals that ARs during wet years are more frequent, and produce heavier precipitation and snow accumulation as compared with dry years.

Scientific Focus Area (SFA): Extreme Events - Infrastructure Resilience

Reference: Eldardiry, H., Mahmood, A., Chen, X., Hossain, F., Nijssen, B., & Lettenmaier, D. P. (2019). Atmospheric River–Induced Precipitation and Snowpack during the Western United States Cold Season. Journal of Hydrometeorology, 20(4), 613-630 (DOI:

On the Use of Radar-based Quantitative Precipitation Estimates for Precipitation Frequency Analysis

This study investigated three fundamental issues that arise when radar-based QPE products are used in frequency analysis: (a) Effect of sample size due to the typically short records of radar products; (b) Effect of uncertainties present in radar-rainfall estimation algorithms; and (c) Effect of the frequency estimation approach adopted. We used a 13-year dataset of hourly, 4x4 km2 radar-based over a domain that covers Louisiana, USA.


Spatial Distribution of the Mean Annual Maxima (MAM) over Louisiana during the study period (2002-2014).

• The relatively short radar records explained the majority of the uncertainty associated with the radar-based quantiles.
• A systematic underestimation bias is observed between radar- and gauge-bases frequency estimates, which was mostly attributable to the conditional bias inherent in the radar product.

Scientific Focus Area (SFA): Remote Sensing - Extreme Events

Reference: Eldardiry, H., Habib, E., & Zhang, Y. (2015). On the use of radar-based quantitative precipitation estimates for precipitation frequency analysis. Journal of Hydrology, 531, 441-453 (DOI:

Artifacts in Stage IV NWS Real-time Multisensor Precipitation Estimates and Impacts on Identification of Maximum Series

This study focuses on data artifacts in the Stage IV radar-based Quantitative Precipitation Estimates (QPE) product over its full record period (2002-2013) and assesses their impacts on the analysis and derivation of heavy rainfall statistics. Examining annual maximum series extracted from the Stage IV 1-h accumulation product revealed the presence of numerous artifacts that were mostly linked to erroneous rain gauge reports and which can be mistaken as rainfall maxima.


First field of Partial Duration Series (PDS) of hourly precipitation (mm) over the CONUS for the period of study, 2002-2013 (maximum value at each individual pixel).

• Artifacts detected in Stage IV QPE had negative impacts on the estimation of parameters and quantiles of commonly-used extreme value probability distributions
• Stage IV 6-h and 24-h accumulations, as well as the longer-latency QPE archive from the regional River Forecasting Centers (RFCs), are mostly free from the artifacts shown in the Stage IV 1-h product.

Scientific Focus Area (SFA): Remote Sensing - Extreme Events

Reference: Eldardiry, H., Habib, E., Zhang, Y., & Graschel, J. (2015). Artifacts in Stage IV NWS real-time multisensor precipitation estimates and impacts on identification of maximum series. Journal of Hydrologic Engineering, 22(5), E4015003. (DOI: