The Lake Tahoe Basin Stream Catchment Database: A resource for water quality monitoring in the basin
Description
Although the Lake Tahoe Basin and its receiving waterbody, Lake Tahoe, are intensively monitored, managed, and studied, there has been no centralized resource for evaluating variation in environmental characteristics among watersheds (i.e., catchments). To address this opportunity, we compiled and calculated 161 variables for 60 non-overlapping contiguous watersheds draining to Lake Tahoe . Watershed-scale variables include climatic, topographic, vegetation, edaphic, hydrologic, and anthropogenic characteristics. Data were downloaded from publicly-available sources including: the National Elevation Dataset, USDA SSURGO soils, Calfire FRAP dataset of fire perimeters, the National Land Cover Dataset, and the Rangeland Analysis Platform. We compiled data in a Geographic Information System at the scale of the watershed. Existing and custom scripts were used to process data and derive variables that could not be obtained from existing databases. These data will be useful for environmental managers and scientists who work in the Lake Tahoe Basin and can assist with future site selection intended to span environmental gradients.
Files
Steps to reproduce
Our dataset includes 161 variables summarized into seven categories. The seven categories are: geographic and shape, hydrologic, anthropogenic, edaphic, land cover, and topographic. The dataset does not include the original raw data since these are all publicly-available, but rather calculates the data for each delineated watershed in an accessible format. Using Dettinger and Rajagopal (2023) as a guide we delineated each stream by filling the 10-meter DEM to remove pits, calculating a flow direction raster, and then calculating a flow accumulation raster using the dam at the outlet of Lake Tahoe as the pour point. All steps were completed using the ArcGIS Pro Spatial Analyst extension (Esri 2023). Next, we manually located pour points to represent each watershed placing each pour point on the highest flow accumulation cell. However, in many cases the spatial locations were too inaccurate or the DEM flow routing necessitated moving the points onto high flow cells. We used topographic maps and the flow accumulation raster to identify the proper pour point. We matched stream delineation to the NHDPlus High Res resulting in all cells with a flow accumulation >5 ha being mapped as streams. We did not use the NHDPlus High Res product directly for stream delineation because of discontinuities in some of the stream networks in our study area (e.g. one stream in Incline Village did not connect to Lake Tahoe). Using the Spatial Analyst extension, we mapped Strahler stream order (Strahler 1957) for all streams in all watersheds. We assigned names to each watershed following the published names by Dettinger and Rajagopal (2023). For most watershed variables we downloaded publicly-available datasets as rasters and calculated the mean, standard deviation, and in some instances, change, and used zonal statistics within the ArcGIS Pro Spatial Analyst extension to write the summary statistics to each watershed. For vector datasets (mostly in the hydrologic group) we used a variety of custom scripts to summarize data to watersheds.
Institutions
- University of Nevada Reno