Urban Evapotranspiration in Water Scarce Regions Estimates for the Middle Rio Grande Region, United States and Mexico
Environmental Engineering Graduate Seminar
As populations increase and climate patterns continue to change, understanding and properly managing water resources is imperative. Estimating urban evapotranspiration (ET) in arid to semi-arid climates is important for water resource management and conservation due to the significant amount of water lost to ET in regions that have warm, dry climates. The purpose of the study is to determine urban ET rates in the Middle Rio Grande Region to support a water balance model by producing a time series of urban ET. The study area includes the cities of Las Cruces, New Mexico; El Paso, Texas; and Cuidad Juarez, Mexico. Changes in climate, water pumping rates and insufficient precipitation to recharge aquifers and surface water sources have caused decreases in water supply leading to water scarcity in these regions. As water scarcity increases, so does the conflict over water rights. Understanding the magnitude of water lost to ET in urban areas will be important for future water use and management decisions.
Components of urban ET include vegetation ET, open water evaporation, evaporation from leaking infrastructure and evaporative coolers. To estimate ET from vegetation, GIS was used with an Operational Simplified Surface Energy Balance (SSEBop) approach along with Normalized Difference Vegetation Index (NDVI) values as a proxy of vegetation greenery. To estimate open water evaporation, Google Earth Engine was used to locate areas of open water in each of the three cities using a script written based on NDVI and color thresholds. Using pan evaporation coefficients, the total area of open water can be calculated and used to determine urban ET from open water sources. Infrastructure leaks were determined from water utility reports and water balances and evaporation from evaporative coolers was calculated based on estimates of evaporative cooler use in each city.
To verify the urban ET, a database of water demands was assembled to separate the urban ET from the total water demand by comparing water use patterns over a historical time period. The urban ET estimates will be included in a broader model to be used for future water resource decision making including impacts of urban water conservation in water scarce regions.
Monday, March 18 at 3:00 pm
Great Lakes Research Center (GLRC), 202
1400 Townsend Drive, Houghton, MI 49931