Water Resources Research Act Program

Details for Project ID 2017OK337B

The Impact of Drought on Vegetation Water Use in Different Climatic Divisions across Oklahoma

Institute: Oklahoma
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $10,000

Principal Investigators: Saleh Taghvaeian, Prasanna Gowda

Project Summary: Water consumed by vegetation is a major component of surface water budget, having a significant impact on water availability at variable scales. The state of Oklahoma lies between the eastern humid and western semi-arid climates including nine climatic divisions (CDs) delineated based on precipitation and temperature gradients. The southeast CD 9 is humid with largest average annual rainfall (57 in), whereas the Panhandle CD 1 is the driest with only 17 in of average annual rainfall. The water use of different types of vegetation is impacted by the variation in climatic conditions, with the same vegetation requiring more water in semi-arid regions than in humid environments. At the same time, the water use and its role in plant health and survival is influenced by drought, a phenomenon that occurs frequently in Oklahoma. Understanding the complex and spatially-variable interactions among vegetation water use, climatic factors, and drought can provide decision maker with critical information required to develop and optimize water management plans to conserve available water resources for agricultural and natural ecosystems. The main objective of this study is to investigate the variations in water use responses for different vegetation types in humid and semi-arid regions of Oklahoma under different levels of drought severity. In this study space-borne remote sensing techniques will be combined with ground-based data to conduct the water use analysis. Freely accessible satellite imagery at appropriate spatial resolution will be used to provide information at individual farm level and sub-basins. A surface energy balance model will be identified and used to map water use estimate across different climatic regions for multiple years with and without drought. The meteorological information will be obtained from the Mesonet weather stations located at each CDs. The study will cover multiple drought events specific to each of CDs including the exceptional drought of 2012. The drought indicator products will be obtained from the US Drought Monitor and other appropriate sources. Landcover data from the USDA National Agricultural Statistics Service (CropScape) will be used for identification of different vegetation types. Irrigated and non-irrigated cropland will be differentiated for water use comparisons based on remotely sensed vegetation indices and surface temperature. Multiple samples of varying sizes from each of the landcover type will be extracted and coupled with drought indices for analyzing water use signals at different climatic environments under variable drought levels. The results from this study include the time series plots of ET from different landcovers. ET maps showing the averages and anomalies at multiple time scales such as month, season and year. Results from this study and meteorological observations from Mesonet stations expect to provide the critical information affecting the water balance at two different climatic divisions of Oklahoma. We expect to see varying ET responses during normal and drought years from different landcovers. For example, above or below average ET among irrigated and non-irrigated agriculture and grasslands during normal year versus during the drought year. Drought impact is expected to be severe and last longer in non-irrigated grasslands or croplands and in forests with lower access to groundwater. These inter-comparisons of ET from multiple landcovers at varying time scale and integrating meteorological information from Mesonet stations expect to improve our understanding on relationships between drought and ET in humid and semi-arid CDs of Oklahoma. After completion of this study, we disseminate our finding by publishing reports, factsheets, and a peer-reviewed journal article.