HydroGETA web service client for ArcGIS

Ernest ToPhD Candidate, University of Texas at

AustinAugust 2008

What is HydroGET?

• A web service client for ESRI‘s ArcGIS environment. • Harvests time series data from web services and stores them in the Arc Hydro data

model.• Default Mode: Downloads data from national data sources to describe

components of the hydrological cycle.

Atmospheric data from Daymet or Unidata

Surface data from USGS NWIS

Subsurface data from USGS NWIS

Illustration courtesy of the United States Geological Survey

• Custom Mode: Downloads data from any combination of CUAHSI web services to describe other properties (e.g. biological) of a study area.

GIS layer that contains points of interest.

List of variables

(each tab holds a different set of variables)

Period of interest

Geodatabase to store downloaded data

Main Interface Types of data and sources

User inputs

Data from user-

specified sources

for single point

Subsurface data

from USGS NWIS

Surface data from

USGS NWIS

Data from user-

specified sources

for multipoints

Atmospheric data

from Daymet and

Unidata Default

Mode

Custom

Mode

HydroGET Interface

The default mode of Weather Downloader describes the hydrological history of a given location by downloading time series from public data repositories.

For this demonstration, we have selected the San Marcos basin in central Texas. The basin is located between the cities of Austin, TX and San Antonio TX. It isis situated over the Edwards Aquifar, a major source of fresh water for the region.

Legend

Watershed centroids (Daymet)

USGS groundwater gages (USGS

NWIS)

USGS streamflow gages (USGS NWIS)

San Marcos basin in central Texas

HydroGET in action (Demo I)

Assembling data for hydrological insightsPrecipitation data from watershed centroids

Streamflow data from USGS gages.

Groundwater data from USGS wells.

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Precipitation (cm)

Streamflow (cfs)

Groundwater level (m above ground surface)

What HydroGET needs to call a web serviceQuery Parameter Explanation Example

WSDL Web Service Description Language (WSDL) http://water.sdsc.edu/wateroneflow/NWIS/DailyValues.asmx?WSDL

NETWORK Name for the sensor network NWIS

SITECODE Site code of the monitoring point 08170500

VARCODE Variable code for the variable of interest 00060

STARTDATE Start date for the period of interest 1/1/2000

ENDDATE End date for the period of interest 12/31/2003

AUTHCODE Authentication code for security reason

Query Parameter Explanation Example

HydroID ID assigned to the site (Long Integer) 1000004

TSTypeID/VarID

ID assigned to the variable(Long Integer)

1003

Underneath the hood

What HydroGET needs to store data in Arc HydroWhat HydroGET needs to store data in Arc Hydro

Making Arc Hydro data user-friendly with SQL queries

Join

Pivot

2. Join

(Use a query to join the TimeSeries table with TSType table and the featureclass attribute table)

3. Pivot

(Pivot the joined table by Variable field to create a MultiColumn table)

MultiColumn table

Joined table

1. Arc Hydro data model

(In Arc Hydro, time series information are stored in three separate tables: TSType, TimeSeries and a featureclass containing the monitoring sites)

Join

Time series format is optimal for storing data but not necessarily for data analysis.

Multicolumn table

• All the time series data from the Arc Hydro geodatabase can be integrated into a single understandable, multicolumn table using queries.

• Each record in the table contains all variables measured at the same point in space and time. Latitude, Longitude, Offset and Time information are also provided within each record.

• Multicolumn format is more amenable to data analysis.

• Because the table is actually a query, when underlying time series data are updated with HydroGET, the multicolumn table gets updated as well.

Conclusions

• HydroGET and MySelect are useful tools for harvesting from CUAHSI web services.

• Semantic differences between different data sources can be mediated by MySelect.

• SQL queries allow instantaneous conversion of Arc Hydro time series into a format suitable for analysis.

• HydroGET is available at http://his.cuahsi.org/hydroget.html