Hydrologic Insights from Recession Curve Analysis and Streamflow Records

Tadhg McGowan^*
*Correspondence: Tadhg McGowan, Department of Civil and Environmental Engineering, Trinity College Dublin, Dublin, Ireland, Email:

Introduction

Recession curve analysis and streamflow records are critical tools in hydrology, providing deep insights into groundwater discharge, aquifer characteristics and watershed behavior. As water moves through a landscape, it infiltrates into the ground, replenishes aquifers and eventually contributes to streamflow through baseflow discharge. The declining limb of a hydrograph known as the recession curve represents this delayed flow of groundwater to surface streams after precipitation events. Analyzing this curve enables hydrologists to estimate key variables such as groundwater recharge rates, storage capacities and the rate at which aquifers release water over time. These parameters are essential for effective water resource planning, especially in regions facing seasonal variability or long-term changes in climate and land use. The United States Geological Survey (USGS), through research and software tools like those developed by Albert T. Rutledge, has greatly advanced the ability to estimate mean groundwater recharge and discharge directly from streamflow records, thus providing a cost-effective and data-driven approach to watershed management [1].

Description

Recession curve analysis typically involves isolating the baseflow portion of a streamflow hydrograph and fitting mathematical models to its downward slope. This decline is assumed to be governed primarily by groundwater contributions, with minimal influence from direct runoff or surface storage. By applying exponential or power-law decay functions, hydrologists can characterize how quickly groundwater drains into streams. These models yield important metrics such as the recession constant and time of drainage, which help quantify aquifer behavior and hydrologic response under varying environmental conditions. Additionally, long-term streamflow records particularly from unregulated or minimally impacted basins are invaluable for recession analysis because they provide a consistent dataset to understand seasonal and inter-annual variations in groundwater discharge. Tools such as RORA (Recession-Only Analysis) and PART (Partitioning of Flow) developed by the USGS have standardized these analyses and enabled hydrologists to automate baseflow separation and recharge estimation using daily streamflow data.

Moreover, recession curve analysis offers broader implications for hydrologic modeling, climate impact assessments and groundwater sustainability. Accurate estimation of mean annual recharge and discharge informs the development of groundwater budgets, critical for understanding aquifer depletion or recovery trends. This is particularly relevant in arid and semi-arid regions, where groundwater may be the primary source of water supply. Through continued calibration using recession parameters, models can simulate future groundwater behavior under various stressors, including urban expansion, land-use changes and increased pumping. The linkage between surface and subsurface hydrology, as revealed by recession data, also supports integrated water management practices that consider the connectivity of streams, wetlands and aquifers. Recession analysis thus provides a vital bridge between raw observational data and practical hydrologic decision-making, ensuring that both quantity and timing of groundwater-sourced flows are adequately understood and preserved [2].

Conclusion

Recession curve analysis and streamflow record interpretation provide powerful insights into the dynamics of groundwater-surface water interactions. By quantifying how aquifers contribute to streamflow over time, hydrologists gain essential knowledge for assessing groundwater sustainability and planning for future water demands. The development and application of tools by institutions like the USGS have made it easier to harness long-term flow data to evaluate recharge and discharge patterns across diverse hydrological settings. As water scarcity and climate variability challenge existing water infrastructure, the continued refinement of recession analysis methods will remain a cornerstone of effective watershed management and sustainable groundwater utilization.

Acknowledgement

None.

Conflict of Interest

None.

References

1. Turnipseed, D. Phil and Vernon B. Sauer. “Discharge measurements at gaging stations.” US Geol Surv

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2. Rutledge, Albert T. “Computer programs for describing the recession of ground-water discharge and for estimating mean ground-water recharge and discharge from streamflow records-update. US Geol Surv

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