Towards a Data Assimilation Framework for Evapotranspiration Over Urban Regions

Project Summary

The hydrological network of the greater Los Angeles County is comprised of many different interactions between the natural and built environment and internal and external changes to the water system. Understanding how water moves through and is stored in this system is the first step towards transitioning to local water usage. This project aims to characterize the evapotranspiration occurring over urban parcels via the integration of a land surface model, a high-resolution land-cover dataset and Bayesian methodologies. The overall goal of the project is to quantify the evapotranspiration over each parcel and its corresponding uncertainty and deliver those estimates to decision makers by means of a web-based user interface. By considering a physically based land-surface model, the evapotranspiration estimates may be updated by assimilating remotely sensed imagery or estimates of outdoor water use from water agencies where available. Finally, through the implementation of land use and climate change scenarios, reserachers expect the model to offer a parcel-level estimate of evapotranspiration (and hence, outdoor water use) under different future conditions. This research effort builds on the team's Los Angeles County water balance study that assessed precipitation, evapotranspiration, imported water, groundwater flows, wastewater flows, stormwater, and consumption demands.

Research Team

Steve Margulis
Civil & Environmental Engineering, Samueli School of Engineering 

Gonzalo Cortés
Civil & Environmental Engineering, Samueli School of Engineering

Progress and Results

This project aims to combine the high-performance computing and modeling in a way that allows an accurate quantification of evapotranspiration over each parcel of the L.A. region. It has the potential to allow home owners to know in detail an estimate of  their own outdoor water use. Furthermore, the framework that we are building is physically based and thus will allow the assimilation of existing and new remote sensing data over the region that could enhance the evapotranspiration estimates.

The project team has generated a comprehensive historical analysis of the primary hydrological fluxes within Los Angeles county, including rainfall, runoff, groundwater recharge, evapotranspiration, imported water and groundwater extractions. This analysis was useful to identify the primary sources of uncertainty in flux estimates, highlighting in particular the need for a more detailed analysis on historical evapotranspiration estimates. This first part of the research has led to the ongoing implementation of land surface model in the Los Angeles county region which is being used to simulate and enhance parcel-level evapotranspiration estimates.


Other Information of Interest

Project graphic showing the cycle of evapotranspiration


Award Year