Last Updated: 1/26/2025
Contact: Bhuwan Ghimire (bhuwan.ghimire@usu.edu)

This resource contains hydroclimate data used in the MS Thesis:
Ghimire, B. (2025). "Investigating Changes in Hydroclimate, Land Cover, and Evapotranspiration across The Great Salt Lake Basin and its Major Subbasins," Civil and Environmental Engineering, Utah State University.

Overview
It contains the data and Python scripts used to extract hydroclimate variables for the subbasins of the Great Salt Lake Basin. Precipitation, air temperature, and evapotranspiration data were retrieved from the 
ClimateEngine platform, while streamflow data was retrieved from the USGS National Water Information System. These variables were averaged over the water years (2004-2021). These data were used to analyze the 
water balance and hydroclimatic trends over the river basins that drain to GSL to investigate causes for changes in lake level.

Data Sources:
ClimateEngine (https://climateengine.com/) - open-access climate cloud computing platform to obtain area-averaged timeseries. The polygons that represent the boundary of the GSL subbasins was delineated from 
the Model My Watershed (https://modelmywatershed.org/) application using USGS gage locations as basin outlet.
USGS (https://waterdata.usgs.gov/nwis/) - Streamflow data from the National Water Information System.

The following hydroclimatic data sources were used:
#1 Precipitation: PRISM (Units: mm)
#2 Daily Mean Air Temperature: PRISM (Units: °C)
#3 Monthly Evapotranspiration: MODIS-ET SSEBop (Units: mm)
#4 Streamflow: USGS (converted to units of mm over the subbasin area)

For consistency, all data were aggregated over the water year.

-------------------- ************** --------------------
Folder Structure
#1. Data_WaterYearAverages
This folder contains water-year averaged data for the following variables:
	Precipitation: PRISM_ppt.csv
	Air Temperature: PRISM_tmean.csv
	Streamflow: streamflow_mm.csv (basin area equivalent streamflow depth)
	Evapotranspiration: USGS_ET_MODIS_MONTHLY_et.csv (depths)

Additional files: Derived from above variables (files)
	Evaporation Ratio   : 	EvaporationRatio.csv
	Runoff Ratio        :	RunoffRatio.csv

Note: The header in these files represents the USGS streamflow gage codes at the outlet of the Bear, Weber, and Jordan River basins:
10126000: Bear River basin
10171000: Jordan River basin
10141000: Weber River basin
Data for some watersheds internal to the major watersheds is also included in these files, but this data was not reported in the study results.

#2. PythonCodes
"ClimateEngine_API_BasinAveraged.ipynb": Customized script to retrieve basin-averaged timeseries data from ClimateEngine API (https://support.climateengine.org/article/42-api-tutorials). Executing this script 
requires an API key from ClimateEngine. The customization enables easy selection of predefined variables using the input Excel file in the "Dependencies_ExcelFiles" folder.
Additional Python scripts in this folder were used for aggregating and visualizing the retrieved timeseries data.

#3. Dependencies_ExcelFiles
This folder contains the input Excel file "Variable_inputs.xlsx", which is used in "ClimateEngine_API_BasinAveraged.ipynb" script. The file defines variables and their abbreviations based on ClimateEngine API 
documentation (https://docs.climateengine.org/docs/build/html/variables.html).
Spatial and temporal resolution and the time period to be used are also set in this file.

#4. Basin_Shapefiles
This folder contains subfolder for the Great Salt Lake subbasins, each with the shapefile that defines the basin/watershed boundary, obtained from the Model My Watershed platform 
(https://modelmywatershed.org/) as USGS streamflow gaging station as the basin outlet.