U.S. Department of the Interior U.S. Geological Survey Reston, Virginia (703) NHD Flow and Velocity Project Greg Schwarz, Reston, VA Alan Rea, Boise, ID

Needed: Estimates of flow and velocity for every reach in NHD Useful for determining:  Dilution of pollutant loadings  Travel time between pollution sources and water intakes  Pollution attenuation with distance

Proposal For every NHD reach, estimate -  Long-term mean annual flow and velocity  Long-term mean monthly flow and velocity  Long-term variance of annual and monthly flow and velocity  Derive 10 th and 90 th percentile flow estimates  7Q10 flow  Measure of statistical accuracy for each estimate

Methodology Statistical approach  Flow estimates best fit the available data  Provides a basis for estimating the accuracy of each estimate Mass balance  Ensures that flow below a confluence equals the sum of the flows entering the confluence  Estimates of non-point pollution concentration derived by dividing non-point pollution load by flow are valid for arbitrarily small basins

Approach Three pilot projects  Arkansas-White-Red River Basin flow pilot  Region of influence regression method  Flow is correlated with basin attributes across a group of basins having similar characteristics.  Large-scale RF1 flow pilot  Spatially Referenced Regression (SPARROW) model of flow applied to all RF1 streams  Simple process oriented model incorporating flow routing from the landscape to RF1 channels.  Flow accumulates according to the defined reach network.

Approach (continued)  Pilot to estimate velocity for every reach in RF1  Regression method (Jobson, 1996)  Time of travel from dye studies  Relate to reach characteristics  flow  slope

The Pilots are Complementary Arkansas-White-Red pilot provides an opportunity to gain experience with NHD and NED. Large-scale RF1 pilots will investigate the diverse processes required to adequately model flow and velocity across the entire nation.

Arkansas-White-Red Pilot Initially computing basin characteristics using EDNA Will be used for first-run model development Initial model calibration

Topographic Basin Characteristics Basin area Mean Basin elevation Basin relief Avg. basin slope Percentage of area with slope >= 30% Synthetic reach slope, node elevations

Thematic Basin Overlays Mean annual precipitation (PRISM) Mean annual temerature (PRISM) Land cover percentages from NLCD, 9 general categories Area-weighted average soil properties from STATSGO Water use by 8-digit HUC Percent area of playas / sand dune regions (AWR only)

Full Scale NHD Project Apply what is learned from the pilots to develop regression-based flow and velocity models for the entire NHD network.

Data Needs NHD reach locations for:  Approximately 4,000 gaging stations with 20 years of record since 1970  76,000 reservoirs from the National Inventory of Dams (NID)  6,600 drinking water intakes  Not required for model estimation but included to provide functionality to the NHD project results.

Other Data Needs Long term mean annual and monthly flow, and variance of annual and monthly flow for over 4,000 gaging stations with 20 years of record since  Data will be compiled from the NWIS data base. Compile over 3,000 velocity measurements from USGS time of travel studies.

Other Data Needs Basin boundaries for every NHD reach  Ongoing effort to derive basin boundaries for every NHD reach having an identified flow direction using the 30m NED. Reach slope  Determine from NED.

Other Data Needs Climate loadings  Precipitation and temperature estimates taken from the Prism climate model. Flow diversions and consumptive use  Water use estimates by hydrologic unit apportioned to reaches on the basis of land use from the NLCD.

Final Products Reach locations for gaging stations, reservoirs, and drinking water intakes. Long-term mean annual and monthly flow and velocity estimates, with estimates of accuracy, for every reach in NHD. Estimates of 10 th and 90 th percentile annual and monthly flows and velocities, and 7Q10 flow, with estimates of accuracy, for every reach in NHD. Results will be made available via the internet. Estimates will be revised periodically as data sets improve.