Datasets derived from Landsat imagery can help guide watershed managers.

(This is the first in a four-part blog series.)

We’re coming to the end of our project to map vegetation trends along the Colorado River, so we’d like to share what SkyTruth has accomplished, what we’ve found, and what others can do to make this work meaningful in their watersheds.

If you’re just starting to explore this project, be sure to have a look at our first few posts to get caught up. You can find my brief overview of the project here, and you can read more about it in a post from Cameron Reaves, one of our recent interns, here.

Background

Our project goal has been to connect vegetation trends over the last 35 years to watershed management and restoration practices. With our data, watershed managers can track vegetation trends through time. And with our soon to be released Issue Map, they can explore how those trends vary spatially across a watershed. Our hope is that managers will be able to identify which particular restoration techniques generate the landscape responses that they want, so they can make better choices in the future about targeting their efforts and resources.

The dataset

We’ve created a 35-year time series of seven different spectral indices for the entire Colorado River drainage using Landsat satellite imagery. The spectral indices that we’ve computed are: the Normalized Difference Vegetation Index (NDVI), the Enhanced Vegetation Index (EVI), the Soil Adjusted Vegetation Index (SAVI), the Modified Soil Adjusted Vegetation Index (MSAVI), the Normalized Difference Moisture Index (NDMI), the Normalized Burn Ratio (NBR), and the Normalized Burn Ratio 2 (NBR2). You can read more about the different indices here, and you can download our 35-year dataset as a CSV file here.

The CSV file contains 7,558 rows (i.e. every subwatershed in the Colorado River drainage) and 471 columns – all 35 years of all spectral indices plus some basic identifying information for each subwatershed (e.g. hydrologic unit code, name, area). We’ve also included a shapefile containing geometries for all of the subwatersheds in the dataset. You can find the shapefile here. Users with a Google Earth Engine account can access them there directly using the hydrologic unit code found in the CSV.

What to expect

We’re planning to release three more blog posts about our work along the Colorado River. Next month, we’ll look at the overall vegetation trends along the river and explore some of the best and worst performers. In August, we’ll release a new Issue Map in SkyTruth Alerts that focuses on the Colorado River, and we’ll zoom in on a few of the watersheds undergoing restoration. And in September, we’ll take a deeper dive into the watersheds where ecological health is up and look at the restoration activities that delivered benefits in multiple watersheds. See you next month!