The University of Arizona

Evaluating Existing and Developing New Drought Indices Using Modeled Soil Moisture Time Series | CLIMAS

Evaluating Existing and Developing New Drought Indices Using Modeled Soil Moisture Time Series

Evaluating Existing and Developing New Drought Indices Using Modeled Soil Moisture Time Series

CLIMAS Lead:  

Our initial project study area is focused on the Las Cienegas National Conservation Area in partnership with the Nature Conservancy (TNC) to examine longer-term drought impacts in a multi-use, Bureau of Land Management NCA. We are working with TNC to develop modeled long-term soil moisture estimates to examine with long-term vegetation monitoring data. This will allow us to assess the impacts of precipitation variability and temperature changes on vegetation production and mortality and identify optimal drought monitoring metrics. We are finding that traditional, simple drought indices like the Standardized Precipitation Index capture complex variability in soil moisture reasonably well at shallow depths. This allows us to recommend using an index like the 2-month SPI to anticipate drought impacts to shallow rooted rangeland vegetation. We are also finding that precipitation variability in winter and summer wet seasons can be used to anticipate soil moisture variability at deeper depths many months later and used as a sort of drought forecasting tool.

A preliminary accomplishment has been in presenting to U.S. Department of Agriculture—Natural Resources Conservation Service (USDA—NRCS) field personnel and establishing some interest in our idea of using soil moisture modeling to assess drought indices. With continued work and engagement with USDA—NRCS we may be able to convince them this is a good strategy to use across their land management units, allowing them to customize their use of drought monitoring indices. We have been working with the Las Cienegas Watershed group as well and may be able to recommend specific drought indices for their ongoing State of the Watershed monitoring. This will become clearer by next spring if they adopt any of our recommendations.