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Shallow Groundwater Estimation (SAGE) for Groundwater Dependent Ecosystems in NV

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Nevada

Publication date: April 1, 2022

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Groundwater levels associated with groundwater-dependent ecosystems in Nevada between 1985 and 2021 were estimated with the Shallow Groundwater Estimation (SAGE) tool developed by The Nature Conservancy in California. The mapped results are found here.

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  • Groundwater

Description

Using a machine learning algorithm developed by TNC-CA (see Rohde et al. 2021), we applied the Shallow Groundwater Estimation (SAGE) tool to estimate groundwater level trends for groundwater dependent ecosystems (GDEs) in Nevada. The tool is applied in Google Earth Engine and uses a Random Forest model that is trained with predictor variables from satellite images,  climate data, and observed groundwater table depths. A Mann-Kendall trend test was used to determine significance of groundwater level trends. By area, we found that 44% of Nevada's GDEs in Nevada were likely associated with groundwater level declines between 1984 and 2021, but monitoring data are lacking at most GDEs in Nevada so more monitoring is needed to verify results. Results are dependent on the quality of the data input to the model, and choice of appropriate predictor variables. For example, locations with very little vegetation like groundwater-dependent playas or lakes may return erroneous results. Python code to apply the tool along with a methods document is available at https://github.com/tnc-ca-geo/SAGE.

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