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RRAWFLOW: Rainfall-Response Aquifer and Watershed Flow Model

Overview of RRAWFLOW

RRAWFLOW is a lumped-parameter model that simulates streamflow, springflow, groundwater level, solute transport, or cave drip for a measurement point in response to a system input of precipitation, recharge, or solute injection. For many applications, a simple lumped model, such as RRAWFLOW, simulates the system response with equal accuracy to that of a complex distributed model. The ease of model construction and calibration makes RRAWFLOW a good choice for many applications, and it provides professional hydrologists and students with an accessible and versatile tool.

RRAWFLOW includes a time-series process to estimate recharge from precipitation and simulates the response to recharge by convolution; that is, the unit-hydrograph approach. Gamma functions are used for estimation of the impulse-response function (IRF), also known as the unit hydrograph, and nonparametric options are available also. Several options are available to simulate time-variant systems.

Some uses of RRAWFLOW to consider:

  • Simulate hydrologic responses to climate projections.
  • Estimate missing periods for a hydrologic monitoring station.
  • Base-flow separation.
  • Investigate time variance, response time, and system memory for a hydrologic system.
  • Edit the code for custom applications.

RRAWFLOW Information and Downloads

The RRAWFLOW program (v1.16) is written in R language. It is not necessary to know the R language to execute the model, but R must be installed on the user’s computer. The file 00_Quick_Start_Guide.pdf, included in the download, will get the R novice started in a short time. The example model can be used as a template to start a new modeling project by editing the input files. The example is set up to run on the Microsoft® Windows operating system but could be slightly modified to run on a Linux operating system.

If parameter optimization is desired, RRAWFLOW can be executed with any optimization routine, including trial and error. The example model is set up for parameter optimization using the PEST software program for model calibration, and the quick-start guide contains instructions for PEST execution.

Example Applications of RRAWFLOW

A preliminary version of RRAWFLOW was developed by Long and Mahler (2013) and used to classify karst aquifers and characterize time-variant systems. This preliminary version also was used by Symtad et al. (2014) to simulate future scenarios of streamflow and groundwater level in a cave in Wind Cave National Park, United States and by the U.S. Geological Survey to simulate future scenarios of springflow and groundwater level in two karst aquifers (

Long, A.J., 2015, RRAWFLOW: Rainfall-Response Aquifer and Watershed Model (v1.15): Geoscientific Model Development, v. 8, p. 865-880,

Long, A.J. and Mahler, B.J., 2013, Prediction, time variance, and classification of hydraulic response to recharge in two karst aquifers: Hydrology and Earth System Sciences, v. 17, p. 281–294. doi:10.5194/hess-17-281-2013

Symstad, A.J., Long, A.J., Stamm, J.F., King, D.A. and Bachelet, D.M., 2014, Two approaches for planning natural resource management in a changing climate at Wind Cave National Park: National Park Service Natural Resource Technical Report NPS/WICA/NRTR—2014/918, 87 p.

Point of Contact

Andrew J. Long, PhD
Research Hydrologist and Groundwater Specialist
U.S. Geological Survey, 934 Braodway, Ste 300, Tacoma, Washington 98402, USA.
Phone: 253-552-1660

Other USGS Groundwater Software

The USGS develops groundwater RSS, water-quality, surface-water, and other water-resources software for use by the USGS in fulfilling its mission. Most of this software is available online for download at no charge.

Disclaimers and Notices

Please refer to the USGS Software User Rights Notice for complete use, copyright, and distribution information. The USGS provides no warranty, expressed or implied, as to the correctness of the furnished software or the suitability for any purpose. The software has been tested, but as with any complex software, there could be undetected errors. Users who find errors are requested to report them to the USGS.

References to non-USGS products, trade names, and (or) services are provided for information purposes only and do not constitute endorsement or warranty, express or implied, by the USGS, U.S. Department of Interior, or U.S. Government, as to their suitability, content, usefulness, functioning, completeness, or accuracy.

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