Shallow groundwater and irrigation are two major factors that may substantially alter water, energy, and carbon fluxes within earth s critical zone. Representing accurate groundwater levels and…

This contract award to Georgia Tech Research Corporation, also known as the Office of Sponsored Programs, is a $446,552 grant for research from the National Aeronautics and Space Administration (NASA) Shared Services Center. The research aims to develop innovative approaches to detect shallow groundwater and irrigation using data from the Soil Moisture Active Passive (SMAP) satellite mission, in order to improve the accuracy of Earth system models in simulating water, energy, and carbon balance components globally. The research will be conducted in four stages, including theoretical foundation, testing, quantifying irrigation, and evaluating the global impacts. This grant does not have a set-aside designation.

Shallow groundwater and irrigation are two major factors that may substantially alter water, energy, and carbon fluxes within earth s critical zone. Representing accurate groundwater levels and irrigation amounts within an earth system model (ESM) is crucially important for proper modeling of the land-atmosphere system. The main goal of this project is to develop innovative, yet simple, approaches to detect shallow groundwater and irrigation based solely on smap images and use the estimates to improve the ability of an ESM to simulate water, energy, and carbon balance components at a global scale. Specific research questions are: (1) how can we detect the influence of shallow groundwater and irrigation from smap observations under various climates and soil textures? (2) can we improve lower boundary conditions of a variably saturated soil moisture flow model solely based on smap dataset without using groundwater observations or groundwater models? (3) how can we account for the influence of irrigation and estimate the amount of irrigation based on smap observations for esms? (4) what are the impacts of shallow groundwater and irrigation on the global water cycle, surface energy balances, and global net ecosystem exchange? Our study will be divided in 4 stages: 1) theoretical foundation: the result of this research is predicated on developing an understanding of the influence of shallow groundwater on surface soil moisture that in turn can be observed by smap. We will use modeling experiments to address the first research question. We will use hydrus-1D to investigate the groundwater influence on surface processes. Our preliminary results show that we can detect the groundwater impacted data points by applying a simple algorithm, which uses thresholds of mean soil moisture and its coefficient of variations as well as a basic block data correction scheme. 2) testing the theory: to address the second research question, we will use smap data to test our approach by focusing on various parts of the world, where shallow groundwater influences surface soil moisture. We will investigate using the smap-based estimates of shallow groundwater to improve the boundary conditions of, and results from, an advanced ESM. A preliminary test using smap data over the pampas region in argentina indicates that we can detect periods of shallow groundwater and improve the model parameterization using the acquired information. 3) quantifying irrigation: to address the third research question, we will develop an algorithm using smap data and a bucket type ecohydrology model to estimate irrigation amounts at global scale. Our preliminary analysis shows that the irrigation amounts during the growing season can be quantified. We will incorporate this information to an ESM by adjusting its upper surface boundary conditions over heavily irrigated regions. 4) evaluating the global impacts: in the final stage, using an advance ecosystem and land surface model (agro-ibis), we will investigate the groundwater and irrigation impacts on global ecosystem exchanges, surface energy fluxes and global water cycle components with more realistic smap-based boundary conditions and high spatial resolution, for the first time. Our research addresses the growing need for new observation-based approaches to quantify the impact of global shallow groundwater and irrigation on esms. The project suggests new uses of smap observations that will be highly beneficial to water, carbon and energy balance related research.