i-Tree Hydro Data Requirements & International Limitations

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i-Tree Hydro Data Requirements & International Limitations

Post by rcoville » Mon Feb 01, 2016 10:40 am

The following information is provided to summarize data requirements and international limitations for users considering using i-Tree Hydro outside the United States. This information is meant to supplement the i-Tree Hydro manual (http://www.itreetools.org/resources/manuals.php) and other documentation which primarily provide details for use of the Hydro model within the United States. The i-Tree Team is currently working with cooperators to improve functionality of the models outside the U.S as time and limited resources will permit.

The data requirements for i-Tree Hydro are as follows, with limitations specific to international projects highlighted in orange.
  1. Project Area information – Defining a project requires setting its location, the project area size, and the time period of simulation, in addition to the inputs described below. In international projects, the location should be set to a reference place within the United States that has similar latitude, elevation, and climate as the actual study area. You can start by looking along a world map on your actual location's latitude, then finding areas in the United States with either similar elevation or similar climate (preferably both) and pick which location you judge as best suited to reflect the conditions of your actual project area. Location data is used to inform weather preprocessing and leaf phenology.
  2. Elevation data – i-Tree Hydro is designed to work with free Digital Elevation Model (DEM) data from the USGS or Topographic Index (TI) data prepared by the i-Tree Team and the USGS. We have pre-loaded TI data for municipalities and watersheds around the United States. For project areas not included in the pre-loaded TI data, users will need to prepare their own DEM for use in i-Tree Hydro.
    For more information on elevation data: viewtopic.php?f=35&t=1240
  3. Land cover data – % tree cover, % of trees that are evergreen, % pervious & impervious cover beneath tree canopy, % shrub cover, % of shrubs that are evergreen, % impervious surface, % of impervious surface which is directly connected, % herbaceous cover, % bare soil cover, % surface water, and other cover types are needed to run the Hydro model. In the United States, most of these values can be obtained from updated National Land Cover Data (NLCD) from the USGS. You can also derive many of these values from i-Tree Canopy, available online at www.itreetools.org/canopy.
    For more information on land cover data: viewtopic.php?f=35&t=1242
  4. Weather data – i-Tree Hydro includes weather data from 2005-2012 for the United States. With some formatting, you can also load your own weather files. i-Tree Hydro is designed to process weather data from the National Climatic Data Center's Integrated Surface Global Hourly stations, which has a specific format you can view here. International users often need to merge their own hourly precipitation time-series into the nearest available NCDC station's data. In the past, the i-Tree Team performed that merger, but at this time limited resources prevent us from providing that support. The i-Tree Database tool is being developed to allow international data to be imported for seamless use in i-Tree Eco and eventually i-Tree Hydro, but it is not ready for use with i-Tree Hydro yet. Currently the easiest option for using weather data from outside of the United States is to use U.S.-based NCDC data, allow Hydro V6 to preprocess it, and then customize the preprocessed file using spreadsheet software (e.g. MS Excel). Instructions on that are described in the FAQ below about customizing timeseries inputs.
    For more information on weather data: viewtopic.php?f=35&t=1248
    For more information on customizing timeseries inputs, which is necessary for merging NCDC data with local hourly precipitation data: viewtopic.php?f=35&t=1400
  5. Hydrological parameters – the model provides Suggested Default Values that can be modified to better represent the specific analysis area. These default values are based on national averages for the United States.
    Stream gauge data is not required and is only needed to use auto-calibration, an optional feature of i-Tree Hydro. With a time-series of stream discharge that corresponds well with good quality weather data, auto-calibration can be used to find a hydrological parameter set which best fits the simulated hydrograph with the observed hydrograph. i-Tree Hydro includes stream data from 2005-2012 for the United States. With some formatting, you can also load your own stream data. Again, stream gauge data is not required to run the model and perform a comparative analysis between land cover scenarios.
    For more information on stream gauge data: viewtopic.php?f=35&t=1249
    For more information on customizing timeseries data, which may be necessary when using international stream gauge data: viewtopic.php?f=35&t=1400
  6. Multiple land use scenarios – i-Tree Hydro can be run for the Base Case to assess current conditions in your project area. To contrast how land cover changes affect the runoff volume and water quality, an Alternative Case can be run. To save time, both Base Case and Alternative Case can be specified at the outset. The Alternative Case can be changed and the model re-run at any time.
In addition to the limitations described above with data requirements, international users should be aware that our water quality estimates are derived from Event Mean Concentration (EMC) values based on studies of pollution in urban areas around the United States. Our pollution estimate method is described in greater detail in the i-Tree Hydro User Manual v5, Appendix 4, Calculating Pollution Load.

Other FAQs about international use that are not listed above:
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