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Arc Hydro: A User’s Experience. Louis Wasson GeoResources Institute Mississippi State University. The Problem. Find rain gauges in a specific watershed There aren’t any … Sorry Model results weren’t representative of the environment. But I was curious. There had to be something better ….
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Arc Hydro: A User’s Experience Louis Wasson GeoResources Institute Mississippi State University UC 2006 Tech Session
The Problem • Find rain gauges in a specific watershed • There aren’t any … Sorry • Model results weren’t representative of the environment But I was curious. There had to be something better … UC 2006 Tech Session
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. UC 2006 Tech Session
Part I. NEXRAD MPE precipitation data What is MPE?? Ground Truthed NEXRAD UC 2006 Tech Session
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. UC 2006 Tech Session
Why use NEXRAD MPE over a surface rain gauge? ETHM6 = 2.6” MPE = 2.25” KSCM6 = 2.38” MPE = 2.4 4km x 4km grid ENBM6 = 1.5” MPE = 1.53” UC 2006 Tech Session
Why use NEXRAD MPE over a surface rain gauge? Rain Gauge NEXRAD MPE UC 2006 Tech Session
Why use NEXRAD MPE over a surface rain gauge? Using MPE NEXRAD precipitation estimates we cover Mississippi almost 8,000 virtual rain gauges! UC 2006 Tech Session
Where can you get NEXRAD MPE data? Quality Controlled daily rainfall estimates. Lower Mississippi River Forecast Center It’s FREE!! http://www.srh.noaa.gov/rfcshare/precip_analysis.php?location=LMRFC UC 2006 Tech Session
Other issues!! • Daily precipitation data comes in Polar Stereographic • Projection. • Hourly data arrives in a xmrg format. • Data is not in TimeSeries format for ArcHydro • applications UC 2006 Tech Session
Part II. • Delineate watershed catchments. • Determine how much rain fell in each catchment. UC 2006 Tech Session
ESRI Arc Hydro Data Model Relationships between objects linked by tracing path of water movement Hydrograph Channels Terrain Surfaces Rainfall Response Digital Orthophotos UC 2006 Tech Session
GeoDatabase? Schema? XML? Feature Class? HydroResponseUnit? Feature DataSet? Extents? UC 2006 Tech Session
ESRI Arc Hydro Data Model Delineate Catchments Hydrologic DEM Outlets Junctions for Each Catchment Hydrologic Network UC 2006 Tech Session
I’ve got delineated catchments and a quality controlled rain fall data source with good spatial coverage. Know how do I get the rain fall data into the catchments? UC 2006 Tech Session
The HydroResponseUnit UC 2006 Tech Session
HydroResponseUnit LMRFC MPE Point Grid UC 2006 Tech Session
Time Series Transfer Rainfall to Catchments UC 2006 Tech Session
In Closing… • Arc Hydro consumes memory quick. Do not work in C: or system drive. Change your environment variables to change your ‘temp’ folder to a larger drive. • If Arc Hydro crashes during the Terrain Processing steps it is usually caused by something in the RivGrid folder. Delete the entire folder. • Understand what a Feature Dataset is all about. Correctly setup it’s spatial properties, especially the limits. You will get ‘out of bounds’ or ‘beyond spatial limit’ errors when you load data into Feature Classes. • HydroID of the HydroResponseUnit polygons must be the same as the FID of your NEXRAD (MPE) data. Use the FID from the MPE point grid you get from the RFC. • Use the CRWR Online Support System! UC 2006 Tech Session