Tuesday - November 14, 2023

 6:00 to 8:00 p.m. PST

​

"Lake Mead Water Quality During a Historic Drought:

Data and Modeling Results"

​

By:  Dr. Todd Tietjen, Dr. Deena Hannoun, and Ms. Charlotte van der Nagel 

 Southern Nevada Water Authority, Las Vegas, Nevada

​

ABSTRACT:

​

The Southern Nevada Water Authority has an extensive water quality monitoring program on Lake Mead and has collected data for over 20 years from this vital resource for the Las Vegas community. This sampling program covers all major inflows to the lake, the Las Vegas Wash, the Virgin and Muddy Rivers, and the Colorado River. Routine monitoring occurs somewhere in the lake every week, with data collected on traditional water quality parameters and parameters of special interest to the drinking water treatment process and drinking water compliance. In addition to this comprehensive sampling program the Water Authority has developed an advanced 3-dimensional, mathematical model of Lake Mead water quality that can be used to explore potential future inflow and outflow scenarios as well as to plan for treatment modifications that would be necessary to address water levels that are beyond actual predicted levels. The majority of the intensive sampling period for Lake Mead has corresponded with the historic drought that began at the turn of the century.  Despite a loss of 75% of the volume of the lake and more than 50 m of surface elevation water quality in the main body of the lake has remained high. Our work suggests that this maintenance of high-water quality resulted from a combination of high levels of wastewater treatment in the Las Vegas Valley, the decreased residence time of water in the lake as water levels fell, and the placement of the reservoir at the bottom of a chain of 3 of the premiere National Parks of the West. 

​

BIOS:

​

Todd Tietjen has been the Regional Water Quality Manager for the Southern Nevada Water Authority for 15 years, working on water quality issues in Lake Mead and the Colorado River Basin with particular focus on issues related to drinking water quality treatment. Todd received his Ph.D. in Aquatic Ecology from the University of Alabama and has previously worked at Mississippi State University and the Grand Canyon Monitoring and Research Center.

​

Deena Hannoun received her BS in Mathematics from James Madison University and her MS & PhD in Applied Mathematics from North Carolina State University.  Deena is the Limnology Modeling Project Manager at the Southern Nevada Water Authority.  She manages the 3D hydrodynamic and water quality model for Lakes Mead and Mohave, as well as performing various modeling tasks on large, diverse data sets.

​

Charlotte van der Nagel is a third year Ph.D. candidate at the Geoscience Department at UNLV. She is originally from the Netherlands and received her MS in Hydrology from the Vrije Universiteit in Amsterdam. Her current research focuses on the effects of climate change on semi-arid ecosystems. She carries out part of her research at SNWA, where she uses hydrodynamic modeling and statistics to study the effects of drought on Lake Mead.