Flow Estimation in Ungaged Basins USGS Progress and Perspectives Julie Kiang, Office of Surface Water Stacey Archfield and Lauren Hay, National Research Program

Contributors Statistical estimation Stacey Archfield, MA WSC Will Farmer, OSW Tom Over, IL WSC Riten Patel, IL WSC David Eash, IA WSC Jon Nania, IA WSC Mike Linhart, IA WSC PRMS development Lauren Hay, NRP Roland Viger, NRP Steve Markstrom, NRP Steve Regan, NRP Andy Bock, NRP Shannon Poole, NRP David Bjerklie, CT WSC John Risley, OR WSC Jeff Tracey, CA WSC PRMS applications Jacob Lafontaine, GA WSC Jeff Riley, GA WSC Ana Maria Garcia, NC WSC Rodney Knight, TN WSC Dan Christiansen, IA WSC Kasey Hutchinson, IA WSC Eddie Haj, IA WSC Parker Norton, ND WSC Portal development Dave Blodgett, CIDA Jordan Walker, CIDA Gap Analysis Dave Stewart, OSW Stacey Archfield, MA WSC Emily Osborne, OSW Ken Eng, NRP Comparisons Jessica Thompson, CIDA Dave Wolock, NAWQA Ken Eng, NRP Plus other WSC staff and students …

Current capabilities for ungaged locations WaterWatch: monthly time series estimates at HUC-8 scale http://waterwatch.usgs.gov StreamStats: estimation of specific flow statistics http://streamstats.usgs.gov/ Local and regional modeling studies Low-resolution national studies

Updating our capabilites National Water Census Objective: To place technical information and tools in the hands of stakeholders, allowing them to answer questions about water availability. Streamflow estimates are needed at ungaged locations National Streamflow Information Program (NSIP) Objectives include: Perform regional streamflow assessments to estimate streamflow at ungaged locations, identify trends, and attempt to determine the cause of trends. John Wesley Powell Center Workgroup Objective: Develop an integrated model approach to estimate streamflow at ungaged locations in the United States

Daily Flow Estimation: Model Comparison Goals for USGS work on ungaged catchments Daily Flow Estimation: Model Comparison Improve temporal and spatial resolution of natural streamflow estimates at ungaged locations throughout the U.S. - daily timestep - 30-year historical period - HUC-12 or better spatial scale Web portal for delivery of results Current work: - testing and enhancing current models - improve understanding of hydrologic similarity and scaling - characterize uncertainty in estimates

Models being considered Type Used Where Dependency on Streamgage Density Drainage Area Ratio (baseline approach) Statistical Widely High Flow Duration Transfer (and variants) MA, PA, NY Analysis of Flow in Networks of Channels (AFINCH) Great Lakes Basin Water Availability Tools for Environmental Resources (WATER) very limited testing Deterministic Watershed KY, NJ, Great Lakes Moderate Precipitation Runoff Modeling System (PRMS) Note: Regional regressions will also be used to estimate specific flow statistics.

All methods require transfer of information from gaged watersheds to ungaged watersheds. Step 1: look at gage network http://pubs.usgs.gov/sir/2013/5013/

Streamgage network: spatial analysis Spatial Gap Analysis Drainage area <=20,000 sq mi 9,674 streamgages 78% coverage

Streamgage network: spatial analysis Spatial Gap Analysis Drainage area <=2,000 sq mi 8,167 streamgages 53% coverage

Streamgage network: spatial analysis Spatial Gap Analysis Drainage area <=1,000 sq mi 7,466 streamgages 37% coverage

Streamgage network: spatial analysis Spatial Gap Analysis Drainage area <=500 sq mi 6,346 streamgages 23% coverage

Availability of long streamflow records Temporal Gap Analysis 8.6% of continental U.S. is gaged by streamgages considered of “reference” quality.

Estimating Stats at Ungaged Locations Estimating streamflow at ungaged sites Estimating Stats at Ungaged Locations Requires the transfer of information from a gaged to an ungaged location. River location Watershed A key assumption: gaged catchments are available which are similar in some way to the ungaged locations. Correlation – tells us about redundancy and where we may need gages (for map correlation) Basin similarity – tells us what basin characteristics we are missing

Correlation Correlation The correlation between streamflow at two gages is one way to assess the potential for successful transfer of information. r = 1: Perfect correlation r = 0: No correlation r = 1 r = 0 Gage B Gage B STREAMFLOW STREAMFLOW Gage A Gage A

Maximum correlation between stations

Models being considered Type Used Where Dependency on Streamgage Density Drainage Area Ratio (baseline approach) Statistical Widely High Flow Duration Transfer (and variants) MA, PA, NY Analysis of Flow in Networks of Channels (AFINCH) Great Lakes Basin Water Availability Tools for Environmental Resources (WATER) very limited testing Deterministic Watershed KY, NJ, Great Lakes Moderate Precipitation Runoff Modeling System (PRMS) Note: Regional regressions will also be used to estimate specific flow statistics.

Southeast U.S. Model Comparison Study Domain

Lots of methods tested – some jump out as being better than others Lots of methods tested – some jump out as being better than others. Note PRMS is very competitive in terms of NSE. Highlighting QPPQ and PRMS as the two models described earlier and the focus of future work.

Looked at lots of different metrics, this for example, NSE but for logs of flows. There we start to see more so that the stats models have advantages. Working on a report that fully documents the analysis.

Trade-off Plot of Model Rankings PRMS NN-SMS12R AFINCH NN-DAR NN-SMS12L NN-SM12 NN-QPPQ Trade-off Plot of Model Rankings Standard deviation of ranking Average mean ranking PRELIMINARY RESULTS

Preliminary results from model comparisons For statistical methods, only able to provide historical estimates and highly dependent on gage network Without calibration, PRMS and other rainfall-runoff models have larger errors Rainfall-runoff models desirable for scenarios (land use change, climate change, etc.) Need method for constraining model parameters at ungaged locations What if we combined modeling approaches to constrain the PRMS model?

Next steps Explore improvements for PRMS bring in information from stats models better understanding of hydrologic similarity and scaling Improve default parameter specification Expand analysis of uncertainty of model results Assess results throughout nation WaterCensus Web portal for streamflow and other components of the water budget Provide tools for ecological analysis