StreamStats: A Web-StreamStats: A Web-Based Tool for Based Tool for

Estimating Streamflow Estimating Streamflow StatisticsStatistics

byby

Alan ReaAlan Rea

and Pete Steevesand Pete Steeves

General description of General description of StreamStatsStreamStats

Web application for stream-flow statistics Web application for stream-flow statistics and basin characteristicsand basin characteristics

GIS-like interfaceGIS-like interface Provides access to GIS data and methodsProvides access to GIS data and methods Gage site and ungaged site proceduresGage site and ungaged site procedures Provides fast, consistent, reproducible Provides fast, consistent, reproducible

resultsresults

National StreamStats StatusNational StreamStats Status

9 states up and running9 states up and running National gages web siteNational gages web site 8-10 more states plan8-10 more states plan

to start up in FY07to start up in FY07 Data upgrades on 3 Data upgrades on 3

states (PA, ID, WA)states (PA, ID, WA) Each state is developedEach state is developed

(and funded) separately(and funded) separately

Overview—Streamflow Overview—Streamflow StatisticsStatistics

What—Estimate of streamflow under What—Estimate of streamflow under some condition, e.g. the 100-year flood some condition, e.g. the 100-year flood flowflow

Why—Engineering design flows for Why—Engineering design flows for structures; many other applicationsstructures; many other applications

How Computed— How Computed— At stream gages: statistical analysis of historic At stream gages: statistical analysis of historic

flowsflows Ungaged sites: Regression equationsUngaged sites: Regression equations

Streamflow Regression Streamflow Regression EquationsEquations

Regression equations take the form:Regression equations take the form:QQ100100 = 758A = 758A0.6430.643PP0.286 0.286 (Wong, 1994)(Wong, 1994)

Drainage area is used in nearly all equationsDrainage area is used in nearly all equations Other common variables include:Other common variables include:

Basin slope, relief, or mean elevationBasin slope, relief, or mean elevation Precipitation (mean annual; 2-year, 24-hour)Precipitation (mean annual; 2-year, 24-hour) Stream length or slopeStream length or slope Land use (forest area, wetland and water areas)Land use (forest area, wetland and water areas) Basin shape or orientationBasin shape or orientation Soils or surficial geologySoils or surficial geology

The benefit of GIS-based toolsThe benefit of GIS-based tools

Cost—Reduce time to delineate and compute Cost—Reduce time to delineate and compute basin characteristics from hours to minutesbasin characteristics from hours to minutes

Accuracy—Some measurements much better, Accuracy—Some measurements much better, others about the same as manual methodsothers about the same as manual methods

Consistency—Important for statistical validityConsistency—Important for statistical validity Reproducibility—Different users will get same Reproducibility—Different users will get same

resultsresults Web-based tool provides broad access to:Web-based tool provides broad access to:

Large geospatial data basesLarge geospatial data bases Consistent methods and dataConsistent methods and data

Some Caveats:Some Caveats:

Estimates are for natural streamflows, Estimates are for natural streamflows, NOTNOT Regulated flows, significant diversions/returnsRegulated flows, significant diversions/returns Gaining/losing reaches, unusual ground-water Gaining/losing reaches, unusual ground-water

influenceinfluence Estimates are not valid for extrapolation Estimates are not valid for extrapolation

outside limits of the regression input data outside limits of the regression input data (given in report)(given in report)

No long-term climate change assumedNo long-term climate change assumed

Application ExamplesApplication Examples

Engineering Design—Bridges, culverts, Engineering Design—Bridges, culverts, flood-plain managementflood-plain management

Water and Land Management—Water Water and Land Management—Water rights adjudication, in-stream flows, fish rights adjudication, in-stream flows, fish passage/habitat studiespassage/habitat studies

Water Quality Regulation—Low flows, Water Quality Regulation—Low flows, perennial vs. intermittent streams (TMDL’s, perennial vs. intermittent streams (TMDL’s, NPDES Permits)NPDES Permits)

Sampling Network Design—Cover a range Sampling Network Design—Cover a range of desired flows of desired flows

The data behind StreamStatsThe data behind StreamStats

Data Sources (flexible)Data Sources (flexible) DEMDEM

• usually NED 10-musually NED 10-m• Can use NHDPlus 30-m grids (Oregon, Wash.) Can use NHDPlus 30-m grids (Oregon, Wash.)

NHD HiRes burned into DEMNHD HiRes burned into DEM WBD walls added to DEM if availableWBD walls added to DEM if available Create DEM derivatives (flowdirection, Create DEM derivatives (flowdirection,

flowaccumulation, etc.)flowaccumulation, etc.) Basin characteristic grids (precip, forest, etc.)Basin characteristic grids (precip, forest, etc.)

The data behind StreamStats (cont)The data behind StreamStats (cont)

Data are brought into ArcHydro using ArcHydro Data are brought into ArcHydro using ArcHydro ToolsTools Most vector data are vectorized DEM derivatives Most vector data are vectorized DEM derivatives

(synthetic hydro)(synthetic hydro) Good alignment with NHD due to burningGood alignment with NHD due to burning Currently we do not use NHD directlyCurrently we do not use NHD directly Plan to add NHD reach/measure and navigation, Plan to add NHD reach/measure and navigation,

event discoveryevent discovery Data are tiled to keep grids smallData are tiled to keep grids small

Usually by 8-digit HUCUsually by 8-digit HUC ““Global” database ties together HUCsGlobal” database ties together HUCs Data can be updated one tile at a timeData can be updated one tile at a time

Global NetworkGlobal Network

Global Directory StructureGlobal Directory Structure

StreamStats is State-CentricStreamStats is State-Centric

Most regression studies state-basedMost regression studies state-based Data needed for a state are built Data needed for a state are built

separately (stove-pipe)separately (stove-pipe) Data usually developed on state’s Data usually developed on state’s

preferred projectionpreferred projection Consequence: More difficult to integrate Consequence: More difficult to integrate

nationallynationally

Tier 1 Consideration for MassachusettsTier 1 Consideration for Massachusetts

Tier 2 Consideration for MassachusettsTier 2 Consideration for Massachusetts

Preprocessing Data for StreamStats Preprocessing Data for StreamStats Includes (among other steps) ….Includes (among other steps) ….

Making a dendrite of the NHD for drainage enforcement (burning-Making a dendrite of the NHD for drainage enforcement (burning-in hydro)in hydro) A consequence of skipping this step may be incorrect watershed A consequence of skipping this step may be incorrect watershed

delineations for locations on the braided sections of a network; headwaters delineations for locations on the braided sections of a network; headwaters that flow in 2 different directions; and at divergences/canals/ditchesthat flow in 2 different directions; and at divergences/canals/ditches

The dendrite was developed in joint maintenance with the WBD (feature The dendrite was developed in joint maintenance with the WBD (feature comparisons resulted in modifications to both datasets on a case-by-case comparisons resulted in modifications to both datasets on a case-by-case basis)basis)

Canals and other man made structures are dealt with on a case by case Canals and other man made structures are dealt with on a case by case basisbasis

The objective to this processing was to develop datasets that would The objective to this processing was to develop datasets that would contribute to accurate watershed delineationscontribute to accurate watershed delineations

Definition of a Dendrite NetworkDefinition of a Dendrite Network

A dendrite is a connected flow network which, if A dendrite is a connected flow network which, if built as a polygon feature class, would produce built as a polygon feature class, would produce zero polygonszero polygons

General RulesGeneral Rules Reaches or parts of reaches could be removed Reaches or parts of reaches could be removed

from the NHD. However, features could not be from the NHD. However, features could not be modified in the NHD.modified in the NHD. The goal was to maintain a spatial link with the source The goal was to maintain a spatial link with the source

datadata

Connectors could be added to the dendrite Connectors could be added to the dendrite WBD inner boundaries could be modifiedWBD inner boundaries could be modified Topographic maps were used in the editing Topographic maps were used in the editing

processprocess

** not all States developed a complete dendrite** not all States developed a complete dendrite

Benefits to NHD StewardsBenefits to NHD Stewards

Dendrite generated connectors could be used Dendrite generated connectors could be used and incorporated into NHD updatesand incorporated into NHD updates

VAA’s such as stream level and stream order VAA’s such as stream level and stream order could be assigned to NHD features in braided could be assigned to NHD features in braided areas based on the dendrite dataareas based on the dendrite data

NHD Navigation in StreamStatsNHD Navigation in StreamStats

NHD functionality in StreamStats will include:NHD functionality in StreamStats will include: Zoom to a reach and measureZoom to a reach and measure Get reach/measure for watershed outletGet reach/measure for watershed outlet Upstream/downstream tracingUpstream/downstream tracing Search on upstream/downstream point and linear Search on upstream/downstream point and linear

eventsevents

Implemented as a web serviceImplemented as a web service

Prototype ArcGIS Server sitePrototype ArcGIS Server site

NHD Navi-gation

NHD Navigation/Reach NHD Navigation/Reach IndexingIndexing

Streamgaging station

User-selected site

Dam site

Point discharge

Water withdrawal

Explanation

Biotic sampling site

StreamStats will provide reach address, consisting of reach number and percentage along reach, for user-selected sites

For more info:For more info:

StreamStats Web SiteStreamStats Web Site

http://streamstats.usgs.gov/http://streamstats.usgs.gov/