About our research

The Role of Sierra Nevada Mountains in Regulating Central Valley Groundwater Recharge

The overall objective of this project is to understand and quantify, the feedback between Sierra Nevada seasonal snow, the GWS in the Central Valley, and the impact of hydro-climatic extremes such as droughts and atmospheric rivers on GWS, while reducing key uncertainties in the current physical understanding of the natural system for guiding hazard monitoring and predictions, thus advancing climate change adaption strategies. We leverage recent advances in satellite observations and modeling to answer the following overarching science question: How much water from the Sierra Nevada's recharges aquifers in the Central Valley via mountain recharge processes, and at what rate?  We include tasks to: 1) Integrate GRACE observations with vertical land motion data to estimate GWS storage change in both deep and shallow aquifers; 2) develop a process-based modeling framework of the Sierra Nevada-Central Valley interface in which land-surface to GWS recharge mechanisms are explicitly represented; 3-4) quantify GWS recharge mechanisms and associated uncertainties by assimilating, among others, the observations derived in 1) within the modeling setup of 2).

Hydrological Predictability and Prediction Skill Associated with Agricultural Practices

Soil Moisture dynamics contribute to the accuracy of sub-seasonal to seasonal forecasts. While natural processes driving soil moisture dynamics (such as precipitation-induced soil wetting) are included in global atmospheric circulation models, anthropogenic processes (such as irrigated agriculture) are rarely modeled. The impact of irrigation on soil moisture variability and soil evaporation depends on the irrigation technique. Innovations in irrigation infrastructure have allowed humanity to utilize previously inaccessible water resources, irrigation techniques, and planting practices to enhance agricultural productivity, often converting rain-fed croplands to irrigated lands. While agricultural intensification is a promising approach to meet the increasing food needs of humanity, it is still unclear to what extent the expansion of irrigated areas, and the related agricultural practices will affect the local, regional, and global climates via teleconnections across temporal scales. Our primary hypothesis is that an improved representation of land atmosphere dynamics can be accomplished if irrigation processes are explicitly coupled within current state-of-the-art Earth Modeling Systems. Specifically, we hypothesize: H1) The explicit representation of agricultural practices allows for improved forecasts skill of sub-seasonal and seasonal models. H2) Through land-atmosphere feedback, agricultural practices may alter the local precipitation regime at the sub-seasonal and seasonal timescale, thereby locally changing the irrigation water needs and availability with the potential to reshape the distribution and extent of areas suitable for irrigation. This feedback may involve teleconnections between irrigation in one region and hydroclimatic conditions in another region. To assess predictability and influence of irrigation practices, we use both observations and model analyses. We introduce an irrigation scheme in the existing GEOS Earth System Modeling framework.