UC 2006 Tech Session 1 Louis Wasson GeoResources Institute Mississippi State University Arc Hydro: A User’s Experience

UC 2006 Tech SessionUC 2006 Tech Session11

Louis WassonGeoResources Institute

Mississippi State University

Arc Hydro: A User’s Experience


The ProblemThe Problem• Find rain gauges in a specific watershedFind rain gauges in a specific watershed

–There aren’t any … SorryThere aren’t any … Sorry

–Model results weren’t representativeModel results weren’t representative

of the environmentof the environment

But I was curious. There had to be something better …


Here’s what I want to do:

Part I. Use NEXRAD Multi-Sensor Precipitation Estimate (MPE)for a better spatial estimation of rainfall.

Part II. Determine how much rain fell into each delineated watershed and how much is flowing out.


Part I. NEXRAD MPE precipitation data

Ground Truthed NEXRAD

What is MPE??What is MPE??


Why use NEXRAD MPE over a surface rain gauge?

A watershed is a rainfall collector with rainfall being the critical driving force in hydrologic modeling.

A rain gauge opening is 8 inches in diameter which is equivalent to 12.5 x 10-9mi2.

Many rain gauges are not in the watershed of interest. Rainfall being based on a few observed points.



KSCM6 = 2.38”

MPE = 2.4

ETHM6 = 2.6”MPE = 2.25”

ENBM6 = 1.5”MPE = 1.53”

4km x 4km grid



Rain Gauge NEXRAD MPE



Using MPE NEXRAD precipitation estimates we cover Mississippi almost 8,000 virtual rain gauges!


Where can you get NEXRAD MPE data?

Quality Controlled daily rainfall estimates.

Lower Mississippi River Forecast Center

http://www.srh.noaa.gov/rfcshare/precip_analysis.php?location=LMRFC

It’s FREE!!


• Daily precipitation data comes in Polar Stereographic Projection.

• Hourly data arrives in a xmrg format.

• Data is not in TimeSeries format for ArcHydro applications

Other issues!!


Part II.Part II.

– Delineate watershed catchments.Delineate watershed catchments.– Determine how much rain fell in each catchment.Determine how much rain fell in each catchment.


ESRI Arc Hydro Data Model

Hydrograph

Channels

Terrain Surfaces

Rainfall Response

Digital Orthophotos

Relationships betweenobjects linked by tracing pathof water movement


GeoDatabase?GeoDatabase? Schema?Schema?XMXML?L?

Feature Class?Feature Class?Feature DataSet?Feature DataSet?Extents?Extents?

HydroResponseUnit?HydroResponseUnit?


ESRI Arc Hydro Data Model

Hydrologic DEM

Delineate Catchments

Outlets Junctions for EachCatchment

HydrologicNetwork


I’ve got delineated catchments and a quality controlled I’ve got delineated catchments and a quality controlled rain fall data source with good spatial coverage.rain fall data source with good spatial coverage.

Know how do I get the rain fall data into the catchments? Know how do I get the rain fall data into the catchments?


The HydroResponseUnitThe HydroResponseUnit


LMRFC MPE Point GridLMRFC MPE Point Grid

HydroResponseUnitHydroResponseUnit


Time SeriesTime Series Transfer Rainfall to CatchmentsTransfer Rainfall to Catchments


• Arc Hydro consumes memory quick. Do not work in C: or system Arc Hydro consumes memory quick. Do not work in C: or system drive. Change your environment variables to change your ‘temp’ drive. Change your environment variables to change your ‘temp’ folder to a larger drive.folder to a larger drive.

• If Arc Hydro crashes during the Terrain Processing steps it is usually If Arc Hydro crashes during the Terrain Processing steps it is usually caused by something in the RivGrid folder. Delete the entire folder.caused by something in the RivGrid folder. Delete the entire folder.

• Understand what a Feature Dataset is all about. Correctly setup it’s Understand what a Feature Dataset is all about. Correctly setup it’s spatial properties, especially the limits. You will get ‘out of bounds’ spatial properties, especially the limits. You will get ‘out of bounds’ or ‘beyond spatial limit’ errors when you load data into Feature or ‘beyond spatial limit’ errors when you load data into Feature Classes.Classes.

• HydroID of the HydroResponseUnit polygons must be the same as HydroID of the HydroResponseUnit polygons must be the same as the FID of your NEXRAD (MPE) data. Use the FID from the MPE the FID of your NEXRAD (MPE) data. Use the FID from the MPE point grid you get from the RFC.point grid you get from the RFC.

• Use the CRWR Online Support System!Use the CRWR Online Support System!

In Closing…In Closing…

Documents

UC 2006 Tech Session 1 Louis Wasson GeoResources Institute Mississippi State University Arc Hydro: A User’s Experience